springboot
Spring Boot Reference Guide
Authors
Phillip Webb, Dave Syer, Josh Long, Stéphane Nicoll, Rob Winch, Andy Wilkinson, Marcel Overdijk, Christian Dupuis, Sébastien Deleuze
1.3.7.RELEASE
Copyright © 2013-2016
Copies of this document may be made for your own use and for distribution to others, provided that you do not charge any fee for such copies and further provided that each copy contains this Copyright Notice, whether distributed in print or electronically.
Table of Contents
I. Spring Boot Documentation
1. About the documentation
2. Getting help
3. First steps
4. Working with Spring Boot
5. Learning about Spring Boot features
6. Moving to production
7. Advanced topics
II. Getting started
8. Introducing Spring Boot
9. System Requirements
9.1. Servlet containers
10. Installing Spring Boot
10.1. Installation instructions for the Java developer
10.1.1. Maven installation
10.1.2. Gradle installation
10.2. Installing the Spring Boot CLI
10.2.1. Manual installation
10.2.2. Installation with SDKMAN!
10.2.3. OSX Homebrew installation
10.2.4. MacPorts installation
10.2.5. Command-line completion
10.2.6. Quick start Spring CLI example
10.3. Upgrading from an earlier version of Spring Boot
11. Developing your first Spring Boot application
11.1. Creating the POM
11.2. Adding classpath dependencies
11.3. Writing the code
11.3.1. The @RestController and @RequestMapping annotations
11.3.2. The @EnableAutoConfiguration annotation
11.3.3。“主要”方法
11.4。运行示例
11.5。创建一个可执行jar
12.接下来要读什么
III。使用Spring Boot
13.构建系统
13.1。依赖管理
13.2。Maven的
13.2.1。继承启动父级
13.2.2。在没有父POM的情况下使用Spring Boot
13.2.3。更改Java版本
13.2.4。使用Spring Boot Maven插件
13.3。摇篮
13.4。蚂蚁
13.5。入门POM
14.构建代码
14.1。使用“默认”包
14.2。找到主应用程序类
15.配置类
15.1。导入其他配置类
15.2。导入XML配置
16.自动配置
16.1。逐渐取代自动配置
16.2。禁用特定的自动配置
17. Spring Beans和依赖注入
18.使用@SpringBootApplication批注
19.运行您的应用程序
19.1。从IDE运行
19.2。作为打包应用程序运行
19.3。使用Maven插件
19.4。使用Gradle插件
19.5。热交换
20.开发人员工具
20.1。属性默认值
20.2。自动重启
20.2.1。不包括资源
20.2.2。看着额外的路径
20.2.3。禁用重启
20.2.4。使用触发器文件
20.2.5。自定义重启类加载器
20.2.6。已知限制
20.3。LiveReload
20.4。全局设置
20.5。远程应用
20.5.1。运行远程客户端应用程序
20.5.2。远程更新
20.5.3。远程调试隧道
21.打包您的应用程序进行生产
22.接下来要读什么
IV。Spring Boot功能
23. SpringApplication
23.1。自定义横幅
23.2。自定义SpringApplication
23.3。流畅的构建器API
23.4。应用程序事件和侦听器
23.5。网络环境
23.6。访问应用程序参数
23.7。使用ApplicationRunner或CommandLineRunner
23.8。申请退出
23.9。管理功能
24.外部配置
24.1。配置随机值
24.2。访问命令行属性
24.3。应用属性文件
24.4。特定于配置文件的属性
24.5。占位符属性
24.6。使用YAML代替Properties
24.6.1。加载YAML
24.6.2。在Spring环境中公开YAML作为属性
24.6.3。多个YAML文档
24.6.4。YAML的缺点
24.7。类型安全的配置属性
24.7.1。第三方配置
24.7.2。轻松绑定
24.7.3。属性转换
24.7.4。@ConfigurationProperties验证
25.简介
25.1。添加活动配置文件
25.2。以编程方式设置配置文
25.3。特定于配置文件的配置文件
26.记录
26.1。日志格式
26.2。控制台输出
26.2.1。彩色编码输出
26.3。文件输出
26.4。日志级别
26.5。自定义日志配置
26.6。Logback扩展
26.6.1。特定于配置文件的配置
26.6.2。环境属性
27.开发Web应用程序
27.1。'Spring Web MVC框架'
27.1.1。Spring MVC自动配置
27.1.2。HttpMessageConverters
27.1.3。MessageCodesResolver的信息
27.1.4。静态内容
27.1.5。ConfigurableWebBindingInitializer
27.1.6。模板引擎
27.1.7。错误处理
WebSphere Application Server上的错误处理
27.1.8。春天的HATEOAS
27.1.9。CORS支持
27.2。JAX-RS和泽西岛
27.3。嵌入式servlet容器支持
27.3.1。Servlet，过滤器和监听器
将Servlet，过滤器和侦听器注册为Spring bean
27.3.2。Servlet上下文初始化
扫描Servlet，过滤器和侦听器
27.3.3。EmbeddedWebApplicationContext
27.3.4。自定义嵌入式servlet容器
程序化定制
直接自定义ConfigurableEmbeddedServletContainer
27.3.5。JSP限制
28.安全
28.1。的OAuth2
28.1.1。授权服务器
28.1.2。资源服务器
28.2。令牌输入用户信息
28.3。自定义用户信息RestTemplate
28.3.1。客户
28.3.2。单点登录
28.4。执行器安全
29.使用SQL数据库
29.1。配置DataSource
29.1.1。嵌入式数据库支持
29.1.2。连接到生产数据库
29.1.3。连接到JNDI数据源
29.2。使用JdbcTemplate
29.3。JPA和'Spring Data'
29.3.1。实体类
29.3.2。Spring Data JPA存储库
29.3.3。创建和删除JPA数据库
29.4。使用H2的Web控制台
29.4.1。更改H2控制台的路径
29.4.2。确保H2控制台的安全
30.使用jOOQ
30.1。代码生成
30.2。使用DSLContext
30.3。自定义jOOQ
31.使用NoSQL技术
31.1。Redis的
31.1.1。连接到Redis
31.2。MongoDB的
31.2.1。连接到MongoDB数据库
31.2.2。MongoTemplate
31.2.3。Spring Data MongoDB存储库
31.2.4。嵌入式Mongo
31.3。的GemFire
31.4。Solr的
31.4.1。连接到Solr
31.4.2。Spring Data Solr存储库
31.5。Elasticsearch
31.5.1。连接到Elasticsearch
31.5.2。Spring Data Elasticsearch存储库
31.6。卡桑德拉
31.6.1。连接到卡桑德拉
31.6.2。Spring Data Cassandra存储库
32.缓存
32.1。支持的缓存提供商
32.1.1。通用
32.1.2。的JCache
32.1.3。EhCache 2.x
32.1.4。Hazelcast
32.1.5。Infinispan的
32.1.6。Redis的
32.1.7。番石榴
32.1.8。简单
33.消息传递
33.1。JMS
33.1.1。ActiveMQ支持
33.1.2。阿尔忒弥斯的支持
33.1.3。HornetQ的支持
33.1.4。使用JNDI ConnectionFactory
33.1.5。发送消息
33.1.6。收到消息
33.2。AMQP
33.2.1。RabbitMQ支持
33.2.2。发送消息
33.2.3。收到消息
34.发送电子邮件
35.使用JTA的分布式事务
35.1。使用Atomikos事务管理器
35.2。使用Bitronix事务管理器
35.3。使用Java EE托管事务管理器
35.4。混合XA和非XA JMS连接
35.5。支持替代嵌入式事务管理器
36. Hazelcast
37.春季整合
38.春季会议
39.对JMX的监督和管理
40.测试
40.1。测试范围依赖性
40.2。测试Spring应用程序
40.3。测试Spring Boot应用程序
40.3.1。使用Spock测试Spring Boot应用程序
40.4。测试工具
40.4.1。ConfigFileApplicationContextInitializer
40.4.2。EnvironmentTestUtils
40.4.3。OutputCapture
40.4.4。TestRestTemplate
41.创建自己的自动配置
41.1。了解自动配置的bean
41.2。找到自动配置候选项
41.3。条件注释
41.3.1。班级条件
41.3.2。豆条件
41.3.3。物业条件
41.3.4。资源条件
41.3.5。Web应用程序条件
41.3.6。SpEL表达条件
41.4。创建自己的启动器
41.4.1。命名
41.4.2。自动配置模块
41.4.3。入门模块
42. WebSockets
43.接下来要读什么
V.弹簧启动执行器：生产就绪功能
44.启用生产就绪功能
45.终点
45.1。自定义端点
45.2。用于执行器MVC端点的超媒体
45.3。CORS支持
45.4。添加自定义端点
45.5。健康信息
45.6。HealthIndicators的安全性
45.6.1。自动配置的HealthIndicators
45.6.2。编写自定义HealthIndicators
45.7。自定义应用信息信息
45.7.1。在构建时自动扩展信息属性
使用Maven自动扩展属性
Automatic property expansion using Gradle
45.7.2. Git commit information
46. Monitoring and management over HTTP
46.1. Securing sensitive endpoints
46.2. Customizing the management endpoint paths
46.3. Customizing the management server port
46.4. Customizing the management server address
46.5. Disabling HTTP endpoints
46.6. HTTP health endpoint access restrictions
47. Monitoring and management over JMX
47.1. Customizing MBean names
47.2. Disabling JMX endpoints
47.3. Using Jolokia for JMX over HTTP
47.3.1. Customizing Jolokia
47.3.2. Disabling Jolokia
48. Monitoring and management using a remote shell
48.1. Connecting to the remote shell
48.1.1. Remote shell credentials
48.2. Extending the remote shell
48.2.1. Remote shell commands
48.2.2. Remote shell plugins
49. Metrics
49.1. System metrics
49.2. DataSource metrics
49.3. Cache metrics
49.4. Tomcat session metrics
49.5。记录您自己的指标
49.6。添加您自己的公共指标
49.7。Java 8的特殊功能
49.8。指标编写者，出口者和聚合
49.8.1。示例：导出到Redis
49.8.2。示例：导出到Open TSDB
49.8.3。示例：导出到Statsd
49.8.4。示例：导出到JMX
49.9。汇总来自多个来源的指标
49.10。Dropwizard指标
49.11。消息通道集成
50.审计
51.追查
51.1。自定义跟踪
52.过程监测
52.1。扩展配置
52.2。编程
53.接下来要读什么
VI。部署Spring Boot应用程序
54.部署到云端
54.1。Cloud Foundry
54.1.1。绑定到服务
54.2。Heroku的
54.3。OpenShift
54.4。Boxfuse和亚马逊网络服务
54.5。Google App Engine
55.安装Spring Boot应用程序
55.1。Unix / Linux服务
55.1.1。作为init.d服务安装（系统V）
保护init.d服务
55.1.2。作为systemd服务安装
55.1.3。自定义启动脚本
55.1.4。使用conf文件自定义启动脚本
56. Microsoft Windows服务
57.接下来要读什么
七。Spring Boot CLI
58.安装CLI
59.使用CLI
59.1。使用CLI运行应用程序
59.1.1。推断“抓住”依赖
59.1.2。推断“抓住”坐标
59.1.3。默认导入语句
59.1.4。自动主要方法
59.1.5。自定义依赖管理
59.2。测试你的代码
59.3。具有多个源文件的应用程序
59.4。打包您的应用程序
59.5。初始化一个新项目
59.6。使用嵌入式shell
59.7。添加CLI扩展
60.使用Groovy bean DSL开发应用程序
61.使用settings.xml配置CLI
62.接下来要读什么
八。构建工具插件
63. Spring Boot Maven插件
63.1。包括插件
63.2。打包可执行jar和war文件
64. Spring Boot Gradle插件
64.1。包括插件
64.2。Gradle依赖管理
64.3。打包可执行jar和war文件
64.4。就地运行项目
64.5。Spring Boot插件配置
64.6。重新包装配置
64.7。使用自定义Gradle配置重新打包
64.7.1。配置选项
64.7.2。可用的布局
64.8。了解Gradle插件的工作原理
64.9。使用Gradle将工件发布到Maven存储库
64.9.1。配置Gradle以生成继承依赖关系管理的pom
64.9.2。配置Gradle以生成导入依赖关系管理的pom
65. Spring Boot AntLib模块
65.1。Spring Boot Ant任务
65.1.1。春季启动：exejar
65.1.2。例子
65.2。春季启动：findmainclass
65.2.1。例子
66.支持其他构建系统
66.1。重新打包档案
66.2。嵌套库
66.3。寻找主要课程
66.4。示例重新打包实现
67.接下来要读什么
IX。'如何'指南
68. Spring Boot应用程序
68.1。排除自动配置故障
68.2。在启动之前自定义Environment或ApplicationContext
68.3。构建ApplicationContext层次结构（添加父或根上下文）
68.4。创建非Web应用程序
69.属性和配置
69.1。外化SpringApplication的配置
69.2。更改应用程序的外部属性的位置
69.3。使用'short'命令行参数
69.4。使用YAML作为外部属性
69.5。设置活动的Spring配置文件
69.6。根据环境更改配置
69.7。发现外部属性的内置选项
70.嵌入式servlet容器
70.1。向应用程序添加Servlet，过滤器或侦听器
70.1.1。使用Spring bean添加Servlet，Filter或Listener
禁用Servlet或Filter的注册
70.1.2。使用类路径扫描添加Servlet，过滤器和侦听器
70.2。更改HTTP端口
70.3。使用随机未分配的HTTP端口
70.4。在运行时发现HTTP端口
70.5。配置SSL
70.6。配置访问日志记录
70.7。在前端代理服务器后面使用
70.7.1。自定义Tomcat的代理配置
70.8。配置Tomcat
70.9。使用Tomcat启用多个连接器
70.10。使用Jetty而不是Tomcat
70.11。配置Jetty
70.12。使用Undertow而不是Tomcat
70.13。配置Undertow
70.14。使用Undertow启用多个侦听器
70.15。使用Tomcat 7
70.15.1。将Tomcat 7与Maven一起使用
70.15.2。将Tomcat 7与Gradle一起使用
70.16。使用Jetty 8
70.16.1。将Jetty 8与Maven一起使用
70.16.2。将Jetty 8与Gradle一起使用
70.17。使用@ServerEndpoint创建WebSocket端点
70.18。启用HTTP响应压缩
71. Spring MVC
71.1。编写JSON REST服务
71.2。编写XML REST服务
71.3。自定义Jackson ObjectMapper
71.4。自定义@ResponseBody渲染
71.5。处理多部分文件上载
71.6。关闭Spring MVC DispatcherServlet
71.7。关闭默认MVC配置
71.8。自定义ViewResolvers
71.9。速度
72.记录
72.1。配置Logback以进行日志记录
72.1.1。配置仅文件输出的回溯
72.2。配置Log4j进行日志记录
72.2.1。使用YAML或JSON配置Log4j 2
73.数据访问
73.1。配置DataSource
73.2。配置两个DataSource
73.3。使用Spring Data存储库
73.4。从Spring配置中分离@Entity定义
73.5。配置JPA属性
73.6。使用自定义EntityManagerFactory
73.7。使用两个EntityManagers
73.8。使用传统的persistence.xml
73.9。使用Spring Data JPA和Mongo存储库
73.10。将Spring Data存储库公开为REST端点
74.数据库初始化
74.1。使用JPA初始化数据库
74.2。使用Hibernate初始化数据库
74.3。使用Spring JDBC初始化数据库
74.4。初始化Spring Batch数据库
74.5。使用更高级别的数据库迁移工具
74.5.1。在启动时执行Flyway数据库迁移
74.5.2。在启动时执行Liquibase数据库迁移
75.批量申请
75.1。在启动时执行Spring Batch作业
76.执行器
76.1。更改执行器端点的HTTP端口或地址
76.2。自定义“whitelabel”错误页面
76.3。执行器和泽西岛
77.安全
77.1。关闭Spring Boot安全配置
77.2。更改AuthenticationManager并添加用户帐户
77.3。在代理服务器后面运行时启用HTTPS
78.热插拔
78.1。重新加载静态内容
78.2。重新加载模板而不重新启动容器
78.2.1。Thymeleaf模板
78.2.2。FreeMarker模板
78.2.3。Groovy模板
78.2.4。速度模板
78.3。快速应用程序重启
78.4。重新加载Java类而不重新启动容器
78.4.1。配置Spring Loaded以与Maven一起使用
78.4.2。配置Spring Loaded以与Gradle和IntelliJ IDEA一起使用
79.建立
79.1。自定义依赖项版本
79.2。使用Maven创建可执行JAR
79.3。创建一个额外的可执行JAR
79.4。可执行jar运行时提取特定库
79.5。使用排除项创建不可执行的JAR
79.6。远程调试使用Maven启动的Spring Boot应用程序
79.7。远程调试使用Gradle启动的Spring Boot应用程序
79.8。不使用spring-boot-antlib从Ant构建可执行归档文件
79.9。如何使用Java 6
79.9.1。嵌入式servlet容器兼容性
79.9.2。JTA API兼容性
80.传统部署
80.1。创建可部署的war文件
80.2。为旧的servlet容器创建可部署的war文件
80.3。将现有应用程序转换为Spring Boot
80.4。将WAR部署到WebLogic
80.5。在旧（Servlet 2.5）容器中部署WAR
X.附录
A.常见应用程序属性
B.配置元数据
B.1。元数据格式
B.1.1。组属性
B.1.2。属性属性
B.1.3。提示属性
B.1.4。重复的元数据项
B.2。提供手动提示
B.2.1。价值提示
B.2.2。价值提供者
任何
课程参考
处理为
记录器名称
Spring bean引用
Spring配置文件名称
B.3。使用注释处理器生成您自己的元数据
B.3.1。嵌套属性
B.3.2。添加其他元数据
C.自动配置类
C.1。来自“spring-boot-autoconfigure”模块
C.2。来自“弹簧 - 启动 - 执行器”模块
D.可执行jar格式
D.1。嵌套的JAR
D.1.1。可执行jar文件结构
D.1.2。可执行的war文件结构
D.2。Spring Boot的“JarFile”类
D.2.1。与标准Java“JarFile”的兼容性
D.3。启动可执行jar
D.3.1。发射器清单
D.3.2。爆炸档案
D.4。PropertiesLauncher功能
D.5。可执行jar限制
D.5.1。Zip条目压缩
D.5.2。系统类加载器
D.6。替代单罐解决方案
E.依赖版本
第一部分Spring Boot文档
本节简要概述了Spring Boot参考文档。将其视为文档其余部分的映射。您可以以线性方式阅读本参考指南，或者如果您不感兴趣，可以跳过章节。
1.关于文档
Spring Boot参考指南以html， pdf 和epub文档的形式提供。最新的副本可在docs.spring.io/spring-boot/docs/current/reference上找到。
本文档的副本可供您自己使用并分发给他人，前提是您不对此类副本收取任何费用，并且每份副本均包含本版权声明，无论是以印刷版还是电子版分发。
2.获得帮助
遇到Spring Boot问题，我们想帮忙！
- Try the How-to’s — they provide solutions to the most common questions.
- Learn the Spring basics — Spring Boot builds on many other Spring projects, check the spring.io web-site for a wealth of reference documentation. If you are just starting out with Spring, try one of the guides.
- Ask a question - we monitor stackoverflow.com for questions tagged with
spring-boot. - Report bugs with Spring Boot at github.com/spring-projects/spring-boot/issues.
| All of Spring Boot is open source, including the documentation! If you find problems with the docs; or if you just want to improve them, please get involved. |
3. First steps
If you’re just getting started with Spring Boot, or 'Spring' in general, this is the place to start!
- From scratch: Overview | Requirements | Installation
- Tutorial: Part 1 | Part 2
- Running your example: Part 1 | Part 2
4. Working with Spring Boot
Ready to actually start using Spring Boot? We’ve got you covered.
- Build systems: Maven | Gradle | Ant | Starter POMs
- Best practices: Code Structure | @Configuration | @EnableAutoConfiguration | Beans and Dependency Injection
- 运行代码 IDE | 打包 | Maven | 摇篮
- 打包您的应用程序： 生产罐
- Spring Boot CLI： 使用CLI
5.了解Spring Boot功能
需要有关Spring Boot核心功能的更多细节？ 这是给你的！
- 核心功能： SpringApplication | 外部配置 | 个人资料 | 记录
- Web应用程序： MVC | 嵌入式容器
- 使用数据： SQL | NO-SQL
- 消息： 概述 | JMS
- 测试： 概述 | 启动应用程序 | utils的
- 扩展： 自动配置 | @条件
6.转向生产
当您准备好将Spring Boot应用程序推向生产时，我们有 一些您可能喜欢的技巧！
- 管理端点： 概述 | 定制
- 连接选项： HTTP | JMX | SSH
- 监控： 指标 | 审计 | 追踪 | 处理
7.高级主题
最后，我们为更高级的用户提供了一些主题。
- 部署Spring Boot应用程序： 云部署 | OS服务
- 构建工具插件： Maven | 摇篮
- 附录： 应用程序属性 | 自动配置类 | 可执行的罐子
第二部分。入门
如果你刚刚开始使用Spring Boot，或者一般来说是“Spring”，那么这就是你的部分！在这里，我们回答基本的“什么？”，“如何？”和“为什么？”的问题。您将找到Spring Boot的简要介绍以及安装说明。然后我们将构建我们的第一个Spring Boot应用程序，讨论一些核心原则。
8.介绍Spring Boot
Spring Boot makes it easy to create stand-alone, production-grade Spring based Applications that you can “just run”. We take an opinionated view of the Spring platform and third-party libraries so you can get started with minimum fuss. Most Spring Boot applications need very little Spring configuration.
You can use Spring Boot to create Java applications that can be started using java -jar or more traditional war deployments. We also provide a command line tool that runs “spring scripts”.
Our primary goals are:
- Provide a radically faster and widely accessible getting started experience for all Spring development.
- Be opinionated out of the box, but get out of the way quickly as requirements start to diverge from the defaults.
- 提供大型项目通用的一系列非功能性功能（例如，嵌入式服务器，安全性，指标，运行状况检查，外部化配置）。
- 绝对没有代码生成，也不需要XML配置。
9.系统要求
默认情况下，Spring Boot 1.3.7.RELEASE需要Java 7和Spring Framework 4.2.7.RELEASE或更高版本。您可以使用带有Java 6的Spring Boot和一些其他配置。有关更多详细信息，请参见第79.9节“如何使用Java 6”。为Maven（3.2+）和Gradle（1.12+）提供显式构建支持。
| 虽然您可以将Spring Boot与Java 6或7一起使用，但我们通常建议尽可能使用Java 8。 |
9.1 Servlet容器
开箱即用支持以下嵌入式servlet容器：
| 名称 | Servlet版本 | Java版本 |
|---|---|---|
| Tomcat 8 |
3.1 |
Java 7+ |
| 雄猫7 |
3.0 |
Java 6+ |
| 码头9 |
3.1 |
Java 7+ |
| 码头8 |
3.0 |
Java 6+ |
| 承诺1.1 |
3.1 |
Java 7+ |
您还可以将Spring Boot应用程序部署到任何Servlet 3.0+兼容容器。
10.安装Spring Boot
Spring Boot可以与“经典”Java开发工具一起使用，也可以作为命令行工具安装。无论如何，您将需要Java SDK v1.6或更高版本。您应该在开始之前检查当前的Java安装：
$ java -version如果您不熟悉Java开发，或者您只是想尝试Spring Boot，则可能需要先尝试Spring Boot CLI，否则请继续阅读“经典”安装说明。
| 尽管Spring Boot与Java 1.6兼容，但如果可能，您应该考虑使用最新版本的Java。 |
10.1 Java开发人员的安装说明
您可以像使用任何标准Java库一样使用Spring Boot。只需spring-boot-*.jar在类路径中包含相应的文件即可。Spring Boot不需要任何特殊工具集成，因此您可以使用任何IDE或文本编辑器; 并且Spring Boot应用程序没有什么特别之处，因此您可以像运行任何其他Java程序一样运行和调试。
虽然您可以复制Spring Boot jar，但我们通常建议您使用支持依赖关系管理的构建工具（例如Maven或Gradle）。
10.1.1 Maven安装
Spring Boot与Apache Maven 3.2或更高版本兼容。如果您还没有安装Maven，可以按照maven.apache.org上的说明进行操作。
| 在许多操作系统上，可以通过包管理器安装Maven。如果您是OSX Homebrew用户，请尝试 |
Spring Boot依赖项使用org.springframework.boot groupId。通常，您的Maven POM文件将从spring-boot-starter-parent项目继承并声明对一个或多个“Starter POM”的依赖关系。Spring Boot还提供了一个可选的 Maven插件来创建可执行jar。
这是一个典型的pom.xml文件：
<？xml version =“1.0”encoding =“UTF-8”？>
xmlns = “http://maven.apache.org/POM/4.0.0” xmlns：xsi = “http：//www.w3 .org / 2001 / XMLSchema-instance“
xsi：schemaLocation = ”http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd“ >
| 这 |
10.1.2 Gradle安装
Spring Boot与Gradle 1.12或更高版本兼容。如果您尚未安装Gradle，则可以按照www.gradle.org/上的说明进行操作。
Spring Boot依赖项可以使用org.springframework.boot group。通常，您的项目将声明对一个或多个“Starter POM”的依赖关系 。Spring Boot提供了一个有用的Gradle插件 ，可用于简化依赖声明和创建可执行jar。
Gradle Wrapper
当您需要构建项目时，Gradle Wrapper提供了一种“获取”Gradle的好方法。这是一个小脚本和库，您可以与代码一起提交以引导构建过程。有关 详细信息，请访问www.gradle.org/docs/current/userguide/gradle_wrapper.html。
这是一个典型的build.gradle文件：
buildscript {
存储库{
jcenter（）
maven {url “http://repo.spring.io/snapshot” }
maven {url “http://repo.spring.io/milestone” }
}
依赖{
classpath（“org.springframework.boot：spring-boot-gradle-plugin：1.3.7.RELEASE”）
}
}
apply plugin：'java'apply
plugin：'spring-boot'
jar {
baseName = 'myproject'version
= '0.0.1-SNAPSHOT'
}
存储库{
jcenter（）
maven {url “http://repo.spring.io/snapshot” }
maven {url “http://repo.spring.io/milestone” }
}
依赖{
编译（“org.springframework.boot：spring-boot-starter-web”）
testCompile（“org.springframework.boot：spring-boot-starter-test”）
}10.2安装Spring Boot CLI
Spring Boot CLI是一个命令行工具，如果您想快速使用Spring进行原型设计，可以使用它。它允许您运行Groovy脚本，这意味着您有一个熟悉的类似Java的语法，没有太多的样板代码。
您不需要使用CLI来使用Spring Boot，但它绝对是实现Spring应用程序的最快方法。
10.2.1手动安装
您可以从Spring软件库下载Spring CLI发行版：
- spring-boot-cli-1.3.7.RELEASE-bin.zip
- 弹簧引导CLI-1.3.7.RELEASE-bin.tar.gz
还提供最先进的快照分发。
下载完成后，请按照 解压缩的存档中的INSTALL.txt说明进行操作。总结：文件中的目录中有一个spring脚本（spring.bat对于Windows），或者您也可以使用该文件（脚本可以帮助您确保正确设置类路径）。bin/.zipjava -jar.jar
10.2.2使用SDKMAN安装！
SDKMAN！（软件开发工具包管理器）可用于管理各种二进制SDK的多个版本，包括Groovy和Spring Boot CLI。获取SDKMAN！来自sdkman.io并安装Spring Boot
$ sdk install springboot
$ spring --version
Spring Boot v1.3.7.RELEASE如果您正在为CLI开发功能并希望轻松访问刚构建的版本，请按照这些额外说明进行操作。
$ sdk install springboot dev /path/to/spring-boot/spring-boot-cli/target/spring-boot-cli-1.3.7.RELEASE-bin/spring-1.3.7.RELEASE/
$ sdk默认springboot dev
$ spring --version
Spring CLI v1.3.7.RELEASE这将安装一个spring名为dev实例的本地实例。它指向您的目标构建位置，因此每次重建Spring Boot时，spring都将是最新的。
你可以通过这样做看到它：
$ sdk是springboot
================================================== ==============================
可用的Springboot版本
================================================== ==============================
> + dev
* 1.3.7.RELEASE
================================================== ==============================
+ - 本地版本
* - 已安装
> - 目前正在使用中
================================================== ==============================10.2.3 OSX Homebrew安装
如果您使用的是Mac并使用Homebrew，那么安装Spring Boot CLI所需要做的就是：
$ brew tap pivotal / tap
$ brew install springbootHomebrew将安装spring到/usr/local/bin。
| 如果您没有看到公式，那么您的brew安装可能已过时。只需执行 |
10.2.4 MacPorts安装
如果您使用的是Mac并使用MacPorts，那么安装Spring Boot CLI所需要做的就是：
$ sudo port install spring-boot-cli10.2.5命令行完成
Spring Boot CLI附带了为BASH和 zsh shell 提供命令完成的脚本 。您可以在任何shell中source使用脚本（也称为 spring），或将其放在个人或系统范围的bash完成初始化中。在Debian系统上，系统范围的脚本都在，/shell-completion/bash 并且当新shell启动时，该目录中的所有脚本都会被执行。要手动运行脚本，例如，如果已使用SDKMAN安装！
$。〜/ .sdkman / springboot /电流/壳完成/庆典/弹簧
$ spring
抓住帮助jar运行测试版 | 如果使用Homebrew或MacPorts安装Spring Boot CLI，命令行完成脚本将自动注册到shell。 |
10.2.6快速启动Spring CLI示例
这是一个非常简单的Web应用程序，可用于测试您的安装。创建一个名为的文件app.groovy：
@RestController
类 ThisWillActuallyRun {
@RequestMapping（ “/”）
String home（）{
“你好，世界！”
}
}然后只需从shell运行它：
$ spring run app.groovy| 首次运行应用程序时需要一些时间，因为下载了依赖项。后续运行会更快。 |
在您喜欢的Web浏览器中打开localhost：8080，您应该看到以下输出：
你好，世界！10.3从早期版本的Spring Boot升级
如果要从早期版本的Spring Boot升级，请检查项目Wiki上托管的“发行说明” 。您将找到升级说明以及每个版本的“新的和值得注意的”功能列表。
要升级现有CLI安装，请使用相应的软件包管理器命令（例如brew upgrade），或者，如果手动安装CLI，请按照 标准说明记住更新PATH环境变量以删除任何旧引用。
11.开发第一个Spring Boot应用程序
让我们用Java开发一个简单的“Hello World！”Web应用程序，它突出了一些Spring Boot的主要功能。我们将使用Maven来构建这个项目，因为大多数IDE都支持它。
| 该spring.io网站包含使用Spring的引导许多“入门”指南。如果你想解决一个特定的问题; 先检查那里。 您可以通过转到start.spring.io并 |
在开始之前，打开终端以检查您是否安装了有效的Java和Maven版本。
$ java -version
java版“1.7.0_51”
Java（TM）SE运行时环境（版本1.7.0_51-b13）
Java HotSpot（TM）64位服务器VM（内置24.51-b03，混合模式）$ mvn -v
Apache Maven 3.2.3（33f8c3e1027c3ddde99d3cdebad2656a31e8fdf4; 2014-08-11T13：58：10-07：00）
Maven home：/Users/user/tools/apache-maven-3.1.1
Java版本：1.7.0_51，供应商：Oracle Corporation| 此示例需要在其自己的文件夹中创建。后续说明假定您已创建了一个合适的文件夹，并且它是您的“当前目录”。 |
11.1创建POM
我们需要从创建Maven pom.xml文件开始。这pom.xml是用于构建项目的配方。打开您喜欢的文本编辑器并添加以下内容：
<？xml version =“1.0”encoding =“UTF-8”？>
xmlns = “http://maven.apache.org/POM/4.0.0” xmlns：xsi = “http：//www.w3 .org / 2001 / XMLSchema-instance“
xsi：schemaLocation = ”http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd“ >
这应该给你一个工作的构建，你可以通过运行测试它mvn package（你可以忽略“jar将是空的 - 没有内容被标记为包含！”警告现在）。
| 此时，您可以将项目导入IDE（大多数现代Java IDE包含对Maven的内置支持）。为简单起见，我们将继续为此示例使用纯文本编辑器。 |
11.2添加类路径依赖项
Spring Boot提供了许多“Starter POM”，可以轻松地将jar添加到类路径中。我们的示例应用程序已经spring-boot-starter-parent在parentPOM部分中使用过 。这spring-boot-starter-parent是一个特殊的启动器，提供有用的Maven默认值。它还提供了一个 dependency-management 部分，以便您可以省略version“祝福”依赖项的标记。
其他“Starter POM”仅提供在开发特定类型的应用程序时可能需要的依赖项。由于我们正在开发一个Web应用程序，我们将添加一个spring-boot-starter-web依赖项 - 但在此之前，让我们看一下我们目前拥有的内容。
$ mvn依赖：树
[INFO] com.example：myproject：jar：0.0.1-SNAPSHOT该mvn dependency:tree命令打印项目依赖项的树表示。您可以看到它spring-boot-starter-parent本身不提供依赖关系。让我们编辑我们pom.xml并spring-boot-starter-web在该parent部分下面添加依赖项：
如果mvn dependency:tree再次运行，您将看到现在有许多其他依赖项，包括Tomcat Web服务器和Spring Boot本身。
11.3编写代码
要完成我们的应用程序，我们需要创建一个Java文件。Maven将src/main/java默认编译源代码，因此您需要创建该文件夹结构，然后添加一个名为的文件src/main/java/Example.java：
import org.springframework.boot。*;
import org.springframework.boot.autoconfigure。*;
import org.springframework.stereotype。*;
import org.springframework.web.bind.annotation。*;
@RestController
@EnableAutoConfiguration
公共 类示例{
@RequestMapping（ “/”）
String home（）{
返回 “Hello World！” ;
}
public static void main（String [] args）throws Exception {
SpringApplication.run（例如.class，args）;
}
}虽然这里的代码不多，但还是有很多代码。让我们逐步完成重要部分。
11.3.1 @RestController和@RequestMapping注释
我们Example班上的第一个注释是@RestController。这被称为 构造型注释。它为阅读代码的人提供了提示，对于Spring，该类扮演着特定的角色。在这种情况下，我们的类是一个Web，@Controller因此Spring在处理传入的Web请求时会考虑它。
该@RequestMapping注释提供“路由”的信息。它告诉Spring，任何带有路径“/”的HTTP请求都应该映射到该home方法。该 @RestController注解告诉Spring使得到的字符串直接返回给调用者。
| 在 |
11.3.2 @EnableAutoConfiguration注释
第二个类级注释是@EnableAutoConfiguration。这个注释告诉Spring Boot根据你添加的jar依赖关系“猜测”你将如何配置Spring。自从spring-boot-starter-web添加了Tomcat和Spring MVC 以来，自动配置将假设您正在开发Web应用程序并相应地设置Spring。
入门POM和自动配置
自动配置旨在与“Starter POM”配合使用，但这两个概念并不直接相关。您可以自由选择启动器POM之外的jar依赖项，Spring Boot仍将尽最大努力自动配置您的应用程序。
11.3.3“主要”方法
我们的应用程序的最后一部分是main方法。这只是遵循应用程序入口点的Java约定的标准方法。我们的main方法SpringApplication通过调用委托给Spring Boot的类run。SpringApplication将引导我们的应用程序，启动Spring，然后启动自动配置的Tomcat Web服务器。我们需要Example.class作为参数传递给run方法，以告诉SpringApplication哪个是主要的Spring组件。该args数组也被传递以公开任何命令行参数。
11.4运行示例
此时我们的应用程序应该可行。由于我们使用了 spring-boot-starter-parentPOM run，因此我们可以使用一个有用的目标来启动应用程序。mvn spring-boot:run从根项目目录中键入以启动应用程序：
$ mvn spring-boot：run
。____ _ __ _ _
/ \\ / ___'_ __ _ _（_）_ __ __ _ \ \ \ \
（（）\ ___ |'_ |'_ | |'_ \ / _` | \ \ \ \
\\ / ___）| | _）| | | | | || （_ | |））））
'| ____ | .__ | _ | | _ | _ | | _ \ __，| / / / / /
========= | _ | ============== | ___ / = / _ / _ / _ /
:: Spring Boot ::（v1.3.7.RELEASE）
....... 。。
....... 。。（此处输出日志）
....... 。。
........ 2.222秒启动示例（JVM运行6.514）如果您将Web浏览器打开到localhost：8080，您应该看到以下输出：
你好，世界！要优雅地退出应用程序命中ctrl-c。
11.5创建可执行jar
让我们通过创建一个完全自包含的可执行jar文件来完成我们的示例，我们可以在生产中运行它。可执行jar（有时称为“fat jar”）是包含已编译类以及代码需要运行的所有jar依赖项的归档。
可执行的jar和Java
Java没有提供任何标准方法来加载嵌套的jar文件（即jar文件本身包含在jar中）。如果您要分发自包含的应用程序，这可能会有问题。
为了解决这个问题，许多开发人员使用“超级”罐子。优步罐只是将所有类中的所有类打包成一个存档。这种方法的问题在于，很难看到您在应用程序中实际使用的库。如果在多个罐子中使用相同的文件名（但具有不同的内容），也可能会有问题。
Spring Boot采用不同的方法，允许您直接嵌套jar。
要创建可执行jar，我们需要添加spring-boot-maven-plugin到我们的 pom.xml。在该dependencies部分正下方插入以下行：
| 所述 |
pom.xml从命令行保存并运行mvn package：
$ mvn包
[INFO]扫描项目......
[信息]
[INFO] ----------------------------------------------- -------------------------
[INFO]构建myproject 0.0.1-SNAPSHOT
[INFO] ----------------------------------------------- -------------------------
[INFO] ....
[INFO] --- maven-jar-plugin：2.4：jar（default-jar）@ myproject ---
[INFO]构建jar：/Users/developer/example/spring-boot-example/target/myproject-0.0.1-SNAPSHOT.jar
[信息]
[INFO] --- spring-boot-maven-plugin：1.3.7.RELEASE：repackage（默认）@ myproject ---
[INFO] ----------------------------------------------- -------------------------
[信息]建立成功
[INFO] ----------------------------------------------- -------------------------如果你查看target目录，你应该看到myproject-0.0.1-SNAPSHOT.jar。该文件大小应为10 Mb左右。如果你想偷看内部，你可以使用jar tvf：
$ jar tvf target / myproject-0.0.1-SNAPSHOT.jar您还应该看到目录中命名myproject-0.0.1-SNAPSHOT.jar.original 的文件小得多target。这是Maven在Spring Boot重新打包之前创建的原始jar文件。
要运行该应用程序，请使用以下java -jar命令：
$ java -jar target / myproject-0.0.1-SNAPSHOT.jar
。____ _ __ _ _
/ \\ / ___'_ __ _ _（_）_ __ __ _ \ \ \ \
（（）\ ___ |'_ |'_ | |'_ \ / _` | \ \ \ \
\\ / ___）| | _）| | | | | || （_ | |））））
'| ____ | .__ | _ | | _ | _ | | _ \ __，| / / / / /
========= | _ | ============== | ___ / = / _ / _ / _ /
:: Spring Boot ::（v1.3.7.RELEASE）
....... 。。
....... 。。（此处输出日志）
....... 。。
........ 2.536秒启动示例（JVM运行2.864）和以前一样，优雅地退出应用程序命中ctrl-c。
12.接下来要读什么
希望本节为您提供了一些Spring Boot基础知识，并帮助您开始编写自己的应用程序。如果您是面向任务的开发人员类型，您可能需要跳转到spring.io并查看一些入门指南，这些指南解决了具体的“如何使用Spring执行此操作”问题; 我们还有Spring Boot特定 的操作方法参考文档。
在春季启动库也有 一堆样品可以运行。样本独立于其余代码（即您无需构建其余代码来运行或使用示例）。
否则，下一个逻辑步骤是阅读第III部分“使用Spring Boot”。如果你真的很不耐烦，你也可以跳过去阅读 Spring Boot功能。
第三部分。使用Spring Boot
本节详细介绍了如何使用Spring Boot。它涵盖了诸如构建系统，自动配置以及如何运行应用程序等主题。我们还介绍了一些Spring Boot最佳实践。虽然Spring Boot没有什么特别之处（它只是你可以使用的另一个库），但有一些建议，如果遵循这些建议，将使您的开发过程更容易一些。
如果您刚刚开始使用Spring Boot，那么在深入了解本节之前，您应该阅读“ 入门指南”。
13.构建系统
强烈建议您选择支持依赖关系管理的构建系统 ，并且可以使用发布到“Maven Central”存储库的工件。我们建议您选择Maven或Gradle。可以让Spring Boot与其他构建系统（例如Ant）一起工作，但它们不会得到特别好的支持。
13.1依赖管理
每个版本的Spring Boot都提供了它支持的依赖项的策划列表。实际上，您不需要为构建配置中的任何这些依赖项提供版本，因为Spring Boot正在为您管理这些依赖项。当您升级Spring Boot时，这些依赖项也将以一致的方式升级。
| 如果您认为有必要，您仍然可以指定版本并覆盖Spring Boot的建议。 |
精选列表包含可以与Spring Boot一起使用的所有spring模块以及精确的第三方库列表。该列表作为标准 物料清单（spring-boot-dependencies）提供， 并且还提供对Maven和 Gradle的额外专用支持。
| 每个版本的Spring Boot都与Spring Framework的基本版本相关联，因此我们强烈建议您不要自己指定它的版本。 |
13.2 Maven
Maven用户可以从spring-boot-starter-parent项目继承以获得合理的默认值。父项目提供以下功能：
- Java 1.6作为默认编译器级别。
- UTF-8源编码。
- 一个依赖管理部分，让您省去
spring-boot-dependenciesPOM。 - 明智的资源过滤。
- 明智的插件配置（exec插件， surefire， Git提交ID， 阴影）。
- 合理的资源过滤
application.properties和application.yml
最后一点：由于默认配置文件接受Spring样式占位符（${…}），Maven过滤被更改为使用@..@占位符（您可以使用Maven属性覆盖它resource.delimiter）。
13.2.1继承启动父级
要将项目配置为从spring-boot-starter-parent简单设置继承parent：
<！ - 继承默认值为Spring Boot - >
| 您只需要在此依赖项上指定Spring Boot版本号。如果导入其他启动器，则可以安全地省略版本号。 |
通过该设置，您还可以通过覆盖自己项目中的属性来覆盖单个依赖项。例如，要升级到另一个Spring Data版本系列，您需要将以下内容添加到您的pom.xml。
releasetrain.version>
Fowler-SR2 | 检查 |
13.2.2在没有父POM的情况下使用Spring Boot
不是每个人都喜欢从spring-boot-starter-parentPOM 继承。您可能拥有自己需要使用的公司标准父级，或者您可能更愿意明确声明所有Maven配置。
如果您不想使用spring-boot-starter-parent，您仍然可以通过使用scope=import 依赖项来保持依赖项管理（但不是插件管理）的好处：
That setup does not allow you to override individual dependencies using a property as explained above. To achieve the same result, you’d need to add an entry in the dependencyManagement of your project before the spring-boot-dependencies entry. For instance, to upgrade to another Spring Data release train you’d add the following to your pom.xml.
| In the example above, we specify a BOM but any dependency type can be overridden that way. |
13.2.3 Changing the Java version
The spring-boot-starter-parent chooses fairly conservative Java compatibility. If you want to follow our recommendation and use a later Java version you can add a java.version property:
13.2.4 Using the Spring Boot Maven plugin
Spring Boot includes a Maven plugin that can package the project as an executable jar. Add the plugin to your
| If you use the Spring Boot starter parent pom, you only need to add the plugin, there is no need for to configure it unless you want to change the settings defined in the parent. |
13.3 Gradle
Gradle users can directly import “starter POMs” in their dependencies section. Unlike Maven, there is no “super parent” to import to share some configuration.
apply plugin: 'java'
repositories {
jcenter()
}
dependencies {
compile("org.springframework.boot:spring-boot-starter-web:1.3.7.RELEASE")
}The spring-boot-gradle-plugin is also available and provides tasks to create executable jars and run projects from source. It also provides dependency management that, among other capabilities, allows you to omit the version number for any dependencies that are managed by Spring Boot:
buildscript {
repositories {
jcenter()
}
dependencies {
classpath("org.springframework.boot:spring-boot-gradle-plugin:1.3.7.RELEASE")
}
}
apply plugin: 'java'
apply plugin: 'spring-boot'
repositories {
jcenter()
}
dependencies {
compile("org.springframework.boot:spring-boot-starter-web")
testCompile("org.springframework.boot:spring-boot-starter-test")
}13.4 Ant
It is possible to build a Spring Boot project using Apache Ant+Ivy. The spring-boot-antlib “AntLib” module is also available to help Ant create executable jars.
To declare dependencies a typical ivy.xml file will look something like this:
version="2.0">
organisation="org.springframework.boot" module="spring-boot-sample-ant" />
name="compile" description="everything needed to compile this module" />
name="runtime" extends="compile" description="everything needed to run this module" />
org="org.springframework.boot" name="spring-boot-starter"
rev="${spring-boot.version}" conf="compile" />
A typical build.xml will look like this:
xmlns:ivy="antlib:org.apache.ivy.ant"
xmlns:spring-boot="antlib:org.springframework.boot.ant"
name="myapp" default="build">
name="spring-boot.version" value="1.3.0.BUILD-SNAPSHOT" />
name="resolve" description="--> retrieve dependencies with ivy">
pattern="lib/[conf]/[artifact]-[type]-[revision].[ext]" />
name="classpaths" depends="resolve">
id="compile.classpath">
dir="lib/compile" includes="*.jar" />
name="init" depends="classpaths">
dir="build/classes" />
name="compile" depends="init" description="compile">
srcdir="src/main/java" destdir="build/classes" classpathref="compile.classpath" />
name="build" depends="compile">
destfile="build/myapp.jar" classes="build/classes">
dir="lib/runtime" />
| See the Section 79.8, “Build an executable archive from Ant without using spring-boot-antlib” “How-to” if you don’t want to use the |
13.5 Starter POMs
Starter POMs are a set of convenient dependency descriptors that you can include in your application. You get a one-stop-shop for all the Spring and related technology that you need, without having to hunt through sample code and copy paste loads of dependency descriptors. For example, if you want to get started using Spring and JPA for database access, just include the spring-boot-starter-data-jpa dependency in your project, and you are good to go.
The starters contain a lot of the dependencies that you need to get a project up and running quickly and with a consistent, supported set of managed transitive dependencies.
What’s in a name
All official starters follow a similar naming pattern; spring-boot-starter-*, where * is a particular type of application. This naming structure is intended to help when you need to find a starter. The Maven integration in many IDEs allow you to search dependencies by name. For example, with the appropriate Eclipse or STS plugin installed, you can simply hit ctrl-space in the POM editor and type “spring-boot-starter” for a complete list.
As explained in the Creating your own starter section, third party starters should not start with spring-boot as it is reserved for official Spring Boot artifacts. A third-party starter for acme will be typically named acme-spring-boot-starter.
The following application starters are provided by Spring Boot under the org.springframework.boot group:
Table 13.1. Spring Boot application starters
| Name | Description |
|---|---|
|
|
The core Spring Boot starter, including auto-configuration support, logging and YAML. |
|
|
Production ready features to help you monitor and manage your application. |
|
|
Support for the “Advanced Message Queuing Protocol” via |
|
|
Support for aspect-oriented programming including |
|
|
Support for “Java Message Service API” via Apache Artemis. |
|
|
Support for “Spring Batch” including HSQLDB database. |
|
|
Support for Spring’s Cache abstraction. |
|
|
Support for “Spring Cloud Connectors” which simplifies connecting to services in cloud platforms like Cloud Foundry and Heroku. |
|
|
Support for the Elasticsearch search and analytics engine including |
|
|
Support for the GemFire distributed data store including |
|
|
Support for the “Java Persistence API” including |
|
|
Support for the MongoDB NoSQL Database, including |
|
|
Support for exposing Spring Data repositories over REST via |
|
|
Support for the Apache Solr search platform, including |
|
|
Support for the FreeMarker templating engine. |
|
|
Support for the Groovy templating engine. |
|
|
Support for HATEOAS-based RESTful services via |
|
|
Support for “Java Message Service API” via HornetQ. |
|
|
Support for common |
|
|
Support for JDBC databases. |
|
|
Support for the Jersey RESTful Web Services framework. |
|
|
Support for JTA distributed transactions via Atomikos. |
|
|
Support for JTA distributed transactions via Bitronix. |
|
|
Support for |
|
|
Support for |
|
|
Support for the Mustache templating engine. |
|
|
Support for the REDIS key-value data store, including |
|
|
Support for |
|
|
Support for |
|
|
Support for |
|
|
Support for |
|
|
Support for common test dependencies, including JUnit, Hamcrest and Mockito along with the |
|
|
Support for the Thymeleaf templating engine, including integration with Spring. |
|
|
Support for the Velocity templating engine. |
|
|
Support for full-stack web development, including Tomcat and |
|
|
Support for WebSocket development. |
|
|
Support for Spring Web Services. |
In addition to the application starters, the following starters can be used to add production ready features.
Table 13.2. Spring Boot production ready starters
| Name | Description |
|---|---|
|
|
Adds production ready features such as metrics and monitoring. |
|
|
Adds remote |
Finally, Spring Boot includes some starters that can be used if you want to exclude or swap specific technical facets.
Table 13.3. Spring Boot technical starters
| Name | Description |
|---|---|
|
|
Imports the Jetty HTTP engine (to be used as an alternative to Tomcat). |
|
|
Support the Log4J logging framework. |
|
|
Import Spring Boot’s default logging framework (Logback). |
|
|
Import Spring Boot’s default HTTP engine (Tomcat). |
|
|
Imports the Undertow HTTP engine (to be used as an alternative to Tomcat). |
| For a list of additional community contributed starter POMs, see the README file in the |
14. Structuring your code
Spring Boot does not require any specific code layout to work, however, there are some best practices that help.
14.1 Using the “default” package
When a class doesn’t include a package declaration it is considered to be in the “default package”. The use of the “default package” is generally discouraged, and should be avoided. It can cause particular problems for Spring Boot applications that use @ComponentScan, @EntityScan or @SpringBootApplication annotations, since every class from every jar, will be read.
| We recommend that you follow Java’s recommended package naming conventions and use a reversed domain name (for example, |
14.2 Locating the main application class
We generally recommend that you locate your main application class in a root package above other classes. The @EnableAutoConfiguration annotation is often placed on your main class, and it implicitly defines a base “search package” for certain items. For example, if you are writing a JPA application, the package of the @EnableAutoConfiguration annotated class will be used to search for @Entity items.
Using a root package also allows the @ComponentScan annotation to be used without needing to specify a basePackage attribute. You can also use the@SpringBootApplication annotation if your main class is in the root package.
Here is a typical layout:
com
+- example
+- myproject
+- Application.java
|
+- domain
| +- Customer.java
| +- CustomerRepository.java
|
+- service
| +- CustomerService.java
|
+- web
+- CustomerController.javaThe Application.java file would declare the main method, along with the basic @Configuration.
package com.example.myproject;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
@Configuration
@EnableAutoConfiguration
@ComponentScan
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
}15. Configuration classes
Spring Boot favors Java-based configuration. Although it is possible to call SpringApplication.run() with an XML source, we generally recommend that your primary source is a @Configuration class. Usually the class that defines the main method is also a good candidate as the primary @Configuration.
| Many Spring configuration examples have been published on the Internet that use XML configuration. Always try to use the equivalent Java-based configuration if possible. Searching for |
15.1 Importing additional configuration classes
You don’t need to put all your @Configuration into a single class. The @Import annotation can be used to import additional configuration classes. Alternatively, you can use @ComponentScan to automatically pick up all Spring components, including @Configuration classes.
15.2 Importing XML configuration
If you absolutely must use XML based configuration, we recommend that you still start with a @Configuration class. You can then use an additional @ImportResource annotation to load XML configuration files.
16. Auto-configuration
Spring Boot auto-configuration attempts to automatically configure your Spring application based on the jar dependencies that you have added. For example, IfHSQLDB is on your classpath, and you have not manually configured any database connection beans, then we will auto-configure an in-memory database.
You need to opt-in to auto-configuration by adding the @EnableAutoConfiguration or @SpringBootApplication annotations to one of your @Configuration classes.
| You should only ever add one |
16.1 Gradually replacing auto-configuration
Auto-configuration is noninvasive, at any point you can start to define your own configuration to replace specific parts of the auto-configuration. For example, if you add your own DataSource bean, the default embedded database support will back away.
If you need to find out what auto-configuration is currently being applied, and why, start your application with the --debug switch. This will log an auto-configuration report to the console.
16.2 Disabling specific auto-configuration
If you find that specific auto-configure classes are being applied that you don’t want, you can use the exclude attribute of @EnableAutoConfiguration to disable them.
import org.springframework.boot.autoconfigure.*;
import org.springframework.boot.autoconfigure.jdbc.*;
import org.springframework.context.annotation.*;
@Configuration
@EnableAutoConfiguration(exclude={DataSourceAutoConfiguration.class})
public class MyConfiguration {
}If the class is not on the classpath, you can use the excludeName attribute of the annotation and specify the fully qualified name instead. Finally, you can also control the list of auto-configuration classes to exclude via the spring.autoconfigure.exclude property.
| You can define exclusions both at the annotation level and using the property. |
17. Spring Beans and dependency injection
You are free to use any of the standard Spring Framework techniques to define your beans and their injected dependencies. For simplicity, we often find that using @ComponentScan to find your beans, in combination with @Autowired constructor injection works well.
If you structure your code as suggested above (locating your application class in a root package), you can add @ComponentScan without any arguments. All of your application components (@Component, @Service, @Repository, @Controller etc.) will be automatically registered as Spring Beans.
Here is an example @Service Bean that uses constructor injection to obtain a required RiskAssessor bean.
package com.example.service;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
@Service
public class DatabaseAccountService implements AccountService {
private final RiskAssessor riskAssessor;
@Autowired
public DatabaseAccountService(RiskAssessor riskAssessor) {
this.riskAssessor = riskAssessor;
}
// ...
}| Notice how using constructor injection allows the |
18. Using the @SpringBootApplication annotation
Many Spring Boot developers always have their main class annotated with @Configuration, @EnableAutoConfiguration and @ComponentScan. Since these annotations are so frequently used together (especially if you follow the best practices above), Spring Boot provides a convenient @SpringBootApplication alternative.
The @SpringBootApplication annotation is equivalent to using @Configuration, @EnableAutoConfiguration and @ComponentScan with their default attributes:
package com.example.myproject;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication // same as @Configuration @EnableAutoConfiguration @ComponentScan
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
}|
|
19. Running your application
One of the biggest advantages of packaging your application as jar and using an embedded HTTP server is that you can run your application as you would any other. Debugging Spring Boot applications is also easy; you don’t need any special IDE plugins or extensions.
| This section only covers jar based packaging, If you choose to package your application as a war file you should refer to your server and IDE documentation. |
19.1 Running from an IDE
You can run a Spring Boot application from your IDE as a simple Java application, however, first you will need to import your project. Import steps will vary depending on your IDE and build system. Most IDEs can import Maven projects directly, for example Eclipse users can select Import… → Existing Maven Projects from the File menu.
If you can’t directly import your project into your IDE, you may be able to generate IDE metadata using a build plugin. Maven includes plugins for Eclipse andIDEA; Gradle offers plugins for various IDEs.
| If you accidentally run a web application twice you will see a “Port already in use” error. STS users can use the |
19.2 Running as a packaged application
If you use the Spring Boot Maven or Gradle plugins to create an executable jar you can run your application using java -jar. For example:
$ java -jar target/myproject-0.0.1-SNAPSHOT.jarIt is also possible to run a packaged application with remote debugging support enabled. This allows you to attach a debugger to your packaged application:
$ java -Xdebug -Xrunjdwp:server=y,transport=dt_socket,address=8000,suspend=n \
-jar target/myproject-0.0.1-SNAPSHOT.jar19.3 Using the Maven plugin
The Spring Boot Maven plugin includes a run goal which can be used to quickly compile and run your application. Applications run in an exploded form just like in your IDE.
$ mvn spring-boot:runYou might also want to use the useful operating system environment variable:
$ export MAVEN_OPTS=-Xmx1024m -XX:MaxPermSize=128M -Djava.security.egd=file:/dev/./urandom(The “egd” setting is to speed up Tomcat startup by giving it a faster source of entropy for session keys.)
19.4 Using the Gradle plugin
The Spring Boot Gradle plugin also includes a bootRun task which can be used to run your application in an exploded form. The bootRun task is added whenever you import the spring-boot-gradle-plugin:
$ gradle bootRunYou might also want to use this useful operating system environment variable:
$ export JAVA_OPTS=-Xmx1024m -XX:MaxPermSize=128M -Djava.security.egd=file:/dev/./urandom19.5 Hot swapping
Since Spring Boot applications are just plain Java applications, JVM hot-swapping should work out of the box. JVM hot swapping is somewhat limited with the bytecode that it can replace, for a more complete solution JRebel or the Spring Loaded project can be used. The spring-boot-devtools module also includes support for quick application restarts.
See the Chapter 20, Developer tools section below and the Hot swapping “How-to” for details.
20. Developer tools
Spring Boot includes an additional set of tools that can make the application development experience a little more pleasant. The spring-boot-devtoolsmodule can be included in any project to provide additional development-time features. To include devtools support, simply add the module dependency to your build:
Maven.
Gradle.
dependencies {
compile("org.springframework.boot:spring-boot-devtools")
}
| Developer tools are automatically disabled when running a fully packaged application. If your application is launched using |
| If you want to ensure that devtools is never included in a production build, you can use the |
20.1 Property defaults
Several of the libraries supported by Spring Boot use caches to improve performance. For example, Thymeleaf will cache templates to save repeatedly parsing XML source files. Whilst caching is very beneficial in production, it can be counter productive during development. If you make a change to a template file in your IDE, you’ll likely want to immediately see the result.
Cache options are usually configured by settings in your application.properties file. For example, Thymeleaf offers the spring.thymeleaf.cacheproperty. Rather than needing to set these properties manually, the spring-boot-devtools module will automatically apply sensible development-time configuration.
| For a complete list of the properties that are applied see DevToolsPropertyDefaultsPostProcessor. |
20.2 Automatic restart
Applications that use spring-boot-devtools will automatically restart whenever files on the classpath change. This can be a useful feature when working in an IDE as it gives a very fast feedback loop for code changes. By default, any entry on the classpath that points to a folder will be monitored for changes. Note that certain resources such as static assets and view templates do not need to restart the application.
Triggering a restart
As DevTools monitors classpath resources, the only way to trigger a restart is to update the classpath. The way in which you cause the classpath to be updated depends on the IDE that you are using. In Eclipse, saving a modified file will cause the classpath to be updated and trigger a restart. In IntelliJ IDEA, building the project (Build → Make Project) will have the same effect.
| You can also start your application via the supported build plugins (i.e. Maven and Gradle) as long as forking is enabled since DevTools need an isolated application classloader to operate properly. You can force the plugin to fork the process as follows: Maven.
Gradle.
|
| Automatic restart works very well when used with LiveReload. See below for details. If you use JRebel automatic restarts will be disabled in favor of dynamic class reloading. Other devtools features (such as LiveReload and property overrides) can still be used. |
| DevTools relies on the application context’s shutdown hook to close it during a restart. It will not work correctly if you have disabled the shutdown hook ( |
| When deciding if an entry on the classpath should trigger a restart when it changes, DevTools automatically ignores projects named |
Restart vs Reload
The restart technology provided by Spring Boot works by using two classloaders. Classes that don’t change (for example, those from third-party jars) are loaded into a base classloader. Classes that you’re actively developing are loaded into a restart classloader. When the application is restarted, the restartclassloader is thrown away and a new one is created. This approach means that application restarts are typically much faster than “cold starts” since the base classloader is already available and populated.
If you find that restarts aren’t quick enough for your applications, or you encounter classloading issues, you could consider reloading technologies such asJRebel from ZeroTurnaround. These work by rewriting classes as they are loaded to make them more amenable to reloading. Spring Loaded provides another option, however it doesn’t support as many frameworks and it isn’t commercially supported.
20.2.1 Excluding resources
Certain resources don’t necessarily need to trigger a restart when they are changed. For example, Thymeleaf templates can just be edited in-place. By default changing resources in /META-INF/maven, /META-INF/resources ,/resources ,/static ,/public or /templates will not trigger a restart but will trigger a live reload. If you want to customize these exclusions you can use the spring.devtools.restart.exclude property. For example, to exclude only/static and /public you would set the following:
spring.devtools.restart.exclude=static/**,public/**| if you want to keep those defaults and add additional exclusions, use the |
20.2.2 Watching additional paths
You may want your application to be restarted or reloaded when you make changes to files that are not on the classpath. To do so, use thespring.devtools.restart.additional-paths property to configure additional paths to watch for changes. You can use the spring.devtools.restart.exclude property described above to control whether changes beneath the additional paths will trigger a full restart or just a live reload.
20.2.3 Disabling restart
If you don’t want to use the restart feature you can disable it using the spring.devtools.restart.enabled property. In most cases you can set this in yourapplication.properties (this will still initialize the restart classloader but it won’t watch for file changes).
If you need to completely disable restart support, for example, because it doesn’t work with a specific library, you need to set a System property before callingSpringApplication.run(…). For example:
public static void main(String[] args) {
System.setProperty("spring.devtools.restart.enabled", "false");
SpringApplication.run(MyApp.class, args);
}20.2.4 Using a trigger file
If you work with an IDE that continuously compiles changed files, you might prefer to trigger restarts only at specific times. To do this you can use a “trigger file”, which is a special file that must be modified when you want to actually trigger a restart check. The trigger file could be updated manually, or via an IDE plugin.
To use a trigger file use the spring.devtools.restart.trigger-file property.
| You might want to set |
20.2.5 Customizing the restart classloader
As described in the Restart vs Reload section above, restart functionality is implemented by using two classloaders. For most applications this approach works well, however, sometimes it can cause classloading issues.
By default, any open project in your IDE will be loaded using the “restart” classloader, and any regular .jar file will be loaded using the “base” classloader. If you work on a multi-module project, and not each module is imported into your IDE, you may need to customize things. To do this you can create a META-INF/spring-devtools.properties file.
The spring-devtools.properties file can contain restart.exclude. and restart.include. prefixed properties. The include elements are items that should be pulled up into the “restart” classloader, and the exclude elements are items that should be pushed down into the “base” classloader. The value of the property is a regex pattern that will be applied to the classpath.
For example:
restart.include.companycommonlibs=/mycorp-common-[\\w-]+\.jar
restart.include.projectcommon=/mycorp-myproj-[\\w-]+\.jar| All property keys must be unique. As long as a property starts with |
| All |
20.2.6 Known limitations
Restart functionality does not work well with objects that are deserialized using a standard ObjectInputStream. If you need to deserialize data, you may need to use Spring’s ConfigurableObjectInputStream in combination with Thread.currentThread().getContextClassLoader().
Unfortunately, several third-party libraries deserialize without considering the context classloader. If you find such a problem, you will need to request a fix with the original authors.
20.3 LiveReload
The spring-boot-devtools module includes an embedded LiveReload server that can be used to trigger a browser refresh when a resource is changed. LiveReload browser extensions are freely available for Chrome, Firefox and Safari from livereload.com.
If you don’t want to start the LiveReload server when your application runs you can set the spring.devtools.livereload.enabled property to false.
| You can only run one LiveReload server at a time, if you start multiple applications from your IDE only the first will have livereload support. |
20.4 Global settings
You can configure global devtools settings by adding a file named .spring-boot-devtools.properties to your $HOME folder (note that the filename starts with “.”). Any properties added to this file will apply to all Spring Boot applications on your machine that use devtools. For example, to configure restart to always use a trigger file, you would add the following:
~/.spring-boot-devtools.properties.
spring.devtools.reload.trigger-file=.reloadtrigger
20.5 Remote applications
The Spring Boot developer tools are not just limited to local development. You can also use several features when running applications remotely. Remote support is opt-in, to enable it you need to set a spring.devtools.remote.secret property. For example:
spring.devtools.remote.secret=mysecret| Enabling |
Remote devtools support is provided in two parts; there is a server side endpoint that accepts connections, and a client application that you run in your IDE. The server component is automatically enabled when the spring.devtools.remote.secret property is set. The client component must be launched manually.
20.5.1 Running the remote client application
The remote client application is designed to be run from within you IDE. You need to runorg.springframework.boot.devtools.RemoteSpringApplication using the same classpath as the remote project that you’re connecting to. The non-option argument passed to the application should be the remote URL that you are connecting to.
For example, if you are using Eclipse or STS, and you have a project named my-app that you’ve deployed to Cloud Foundry, you would do the following:
- Select
Run Configurations…from theRunmenu. - Create a new
Java Application“launch configuration”. - Browse for the
my-appproject. - Use
org.springframework.boot.devtools.RemoteSpringApplicationas the main class. - Add
https://myapp.cfapps.ioto theProgram arguments(or whatever your remote URL is).
A running remote client will look like this:
. ____ _ __ _ _
/\\ / ___'_ __ _ _(_)_ __ __ _ ___ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | | _ \___ _ __ ___| |_ ___ \ \ \ \
\\/ ___)| |_)| | | | | || (_| []::::::[] / -_) ' \/ _ \ _/ -_) ) ) ) )
' |____| .__|_| |_|_| |_\__, | |_|_\___|_|_|_\___/\__\___|/ / / /
=========|_|==============|___/===================================/_/_/_/
:: Spring Boot Remote :: 1.3.7.RELEASE
2015-06-10 18:25:06.632 INFO 14938 --- [ main] o.s.b.devtools.RemoteSpringApplication : Starting RemoteSpringApplication on pwmbp with PID 14938 (/Users/pwebb/projects/spring-boot/code/spring-boot-devtools/target/classes started by pwebb in /Users/pwebb/projects/spring-boot/code/spring-boot-samples/spring-boot-sample-devtools)
2015-06-10 18:25:06.671 INFO 14938 --- [ main] s.c.a.AnnotationConfigApplicationContext : Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@2a17b7b6: startup date [Wed Jun 10 18:25:06 PDT 2015]; root of context hierarchy
2015-06-10 18:25:07.043 WARN 14938 --- [ main] o.s.b.d.r.c.RemoteClientConfiguration : The connection to http://localhost:8080 is insecure. You should use a URL starting with 'https://'.
2015-06-10 18:25:07.074 INFO 14938 --- [ main] o.s.b.d.a.OptionalLiveReloadServer : LiveReload server is running on port 35729
2015-06-10 18:25:07.130 INFO 14938 --- [ main] o.s.b.devtools.RemoteSpringApplication : Started RemoteSpringApplication in 0.74 seconds (JVM running for 1.105)| Because the remote client is using the same classpath as the real application it can directly read application properties. This is how the |
| It’s always advisable to use |
| If you need to use a proxy to access the remote application, configure the |
20.5.2 Remote update
The remote client will monitor your application classpath for changes in the same way as the local restart. Any updated resource will be pushed to the remote application and (if required) trigger a restart. This can be quite helpful if you are iterating on a feature that uses a cloud service that you don’t have locally. Generally remote updates and restarts are much quicker than a full rebuild and deploy cycle.
| Files are only monitored when the remote client is running. If you change a file before starting the remote client, it won’t be pushed to the remote server. |
20.5.3 Remote debug tunnel
Java remote debugging is useful when diagnosing issues on a remote application. Unfortunately, it’s not always possible to enable remote debugging when your application is deployed outside of your data center. Remote debugging can also be tricky to setup if you are using a container based technology such as Docker.
To help work around these limitations, devtools supports tunneling of remote debug traffic over HTTP. The remote client provides a local server on port 8000that you can attach a remote debugger to. Once a connection is established, debug traffic is sent over HTTP to the remote application. You can use the spring.devtools.remote.debug.local-port property if you want to use a different port.
You’ll need to ensure that your remote application is started with remote debugging enabled. Often this can be achieved by configuring JAVA_OPTS. For example, with Cloud Foundry you can add the following to your manifest.yml:
---
env:
JAVA_OPTS: "-Xdebug -Xrunjdwp:server=y,transport=dt_socket,suspend=n"| Notice that you don’t need to pass an |
| Debugging a remote service over the Internet can be slow and you might need to increase timeouts in your IDE. For example, in Eclipse you can select |
21. Packaging your application for production
Executable jars can be used for production deployment. As they are self-contained, they are also ideally suited for cloud-based deployment.
For additional “production ready” features, such as health, auditing and metric REST or JMX end-points; consider adding spring-boot-actuator. See Part V, “Spring Boot Actuator: Production-ready features” for details.
22. What to read next
You should now have good understanding of how you can use Spring Boot along with some best practices that you should follow. You can now go on to learn about specific Spring Boot features in depth, or you could skip ahead and read about the “production ready” aspects of Spring Boot.
Part IV. Spring Boot features
This section dives into the details of Spring Boot. Here you can learn about the key features that you will want to use and customize. If you haven’t already, you might want to read the Part II, “Getting started” and Part III, “Using Spring Boot” sections so that you have a good grounding of the basics.
23. SpringApplication
The SpringApplication class provides a convenient way to bootstrap a Spring application that will be started from a main() method. In many situations you can just delegate to the static SpringApplication.run method:
public static void main(String[] args) {
SpringApplication.run(MySpringConfiguration.class, args);
}When your application starts you should see something similar to the following:
. ____ _ __ _ _
/\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
\\/ ___)| |_)| | | | | || (_| | ) ) ) )
' |____| .__|_| |_|_| |_\__, | / / / /
=========|_|==============|___/=/_/_/_/
:: Spring Boot :: v1.3.7.RELEASE
2013-07-31 00:08:16.117 INFO 56603 --- [ main] o.s.b.s.app.SampleApplication : Starting SampleApplication v0.1.0 on mycomputer with PID 56603 (/apps/myapp.jar started by pwebb)
2013-07-31 00:08:16.166 INFO 56603 --- [ main] ationConfigEmbeddedWebApplicationContext : Refreshing org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@6e5a8246: startup date [Wed Jul 31 00:08:16 PDT 2013]; root of context hierarchy
2014-03-04 13:09:54.912 INFO 41370 --- [ main] .t.TomcatEmbeddedServletContainerFactory : Server initialized with port: 8080
2014-03-04 13:09:56.501 INFO 41370 --- [ main] o.s.b.s.app.SampleApplication : Started SampleApplication in 2.992 seconds (JVM running for 3.658)By default INFO logging messages will be shown, including some relevant startup details such as the user that launched the application.
23.1 Customizing the Banner
The banner that is printed on start up can be changed by adding a banner.txt file to your classpath, or by setting banner.location to the location of such a file. If the file has an unusual encoding you can set banner.charset (default is UTF-8).
You can use the following variables inside your banner.txt file:
Table 23.1. Banner variables
| Variable | Description |
|---|---|
|
|
The version number of your application as declared in |
|
|
The version number of your application as declared in |
|
|
The Spring Boot version that you are using. For example |
|
|
The Spring Boot version that you are using formatted for display (surrounded with brackets and prefixed with |
|
|
Where |
|
|
The title of your application as declared in |
| The |
You can also use the spring.main.banner-mode property to determine if the banner has to be printed on System.out (console), using the configured logger (log) or not at all (off).
| YAML maps |
23.2 Customizing SpringApplication
If the SpringApplication defaults aren’t to your taste you can instead create a local instance and customize it. For example, to turn off the banner you would write:
public static void main(String[] args) {
SpringApplication app = new SpringApplication(MySpringConfiguration.class);
app.setBannerMode(Banner.Mode.OFF);
app.run(args);
}| The constructor arguments passed to |
It is also possible to configure the SpringApplication using an application.properties file. See Chapter 24, Externalized Configuration for details.
For a complete list of the configuration options, see the SpringApplication Javadoc.
23.3 Fluent builder API
If you need to build an ApplicationContext hierarchy (multiple contexts with a parent/child relationship), or if you just prefer using a ‘fluent’ builder API, you can use the SpringApplicationBuilder.
The SpringApplicationBuilder allows you to chain together multiple method calls, and includes parent and child methods that allow you to create a hierarchy.
For example:
new SpringApplicationBuilder()
.bannerMode(Banner.Mode.OFF)
.sources(Parent.class)
.child(Application.class)
.run(args);| There are some restrictions when creating an |
23.4 Application events and listeners
In addition to the usual Spring Framework events, such as ContextRefreshedEvent, a SpringApplication sends some additional application events.
| Some events are actually triggered before the If you want those listeners to be registered automatically regardless of the way the application is created you can add a |
Application events are sent in the following order, as your application runs:
- An
ApplicationStartedEventis sent at the start of a run, but before any processing except the registration of listeners and initializers. - An
ApplicationEnvironmentPreparedEventis sent when theEnvironmentto be used in the context is known, but before the context is created. - An
ApplicationPreparedEventis sent just before the refresh is started, but after bean definitions have been loaded. - An
ApplicationReadyEventis sent after the refresh and any related callbacks have been processed to indicate the application is ready to service requests. - An
ApplicationFailedEventis sent if there is an exception on startup.
| You often won’t need to use application events, but it can be handy to know that they exist. Internally, Spring Boot uses events to handle a variety of tasks. |
23.5 Web environment
A SpringApplication will attempt to create the right type of ApplicationContext on your behalf. By default, an AnnotationConfigApplicationContext or AnnotationConfigEmbeddedWebApplicationContext will be used, depending on whether you are developing a web application or not.
The algorithm used to determine a ‘web environment’ is fairly simplistic (based on the presence of a few classes). You can use setWebEnvironment(boolean webEnvironment) if you need to override the default.
It is also possible to take complete control of the ApplicationContext type that will be used by calling setApplicationContextClass(…).
| It is often desirable to call |
23.6 Accessing application arguments
If you need to access the application arguments that were passed to SpringApplication.run(…) you can inject aorg.springframework.boot.ApplicationArguments bean. The ApplicationArguments interface provides access to both the raw String[] arguments as well as parsed option and non-option arguments:
import org.springframework.boot.*
import org.springframework.beans.factory.annotation.*
import org.springframework.stereotype.*
@Component
public class MyBean {
@Autowired
public MyBean(ApplicationArguments args) {
boolean debug = args.containsOption("debug");
List files = args.getNonOptionArgs();
// if run with "--debug logfile.txt" debug=true, files=["logfile.txt"]
}
} | Spring Boot will also register a |
23.7 Using the ApplicationRunner or CommandLineRunner
If you need to run some specific code once the SpringApplication has started, you can implement the ApplicationRunner or CommandLineRunnerinterfaces. Both interfaces work in the same way and offer a single run method which will be called just before SpringApplication.run(…) completes.
The CommandLineRunner interfaces provides access to application arguments as a simple string array, whereas the ApplicationRunner uses the ApplicationArguments interface discussed above.
import org.springframework.boot.*
import org.springframework.stereotype.*
@Component
public class MyBean implements CommandLineRunner {
public void run(String... args) {
// Do something...
}
}You can additionally implement the org.springframework.core.Ordered interface or use the org.springframework.core.annotation.Orderannotation if several CommandLineRunner or ApplicationRunner beans are defined that must be called in a specific order.
23.8 Application exit
Each SpringApplication will register a shutdown hook with the JVM to ensure that the ApplicationContext is closed gracefully on exit. All the standard Spring lifecycle callbacks (such as the DisposableBean interface, or the @PreDestroy annotation) can be used.
In addition, beans may implement the org.springframework.boot.ExitCodeGenerator interface if they wish to return a specific exit code when the application ends.
23.9 Admin features
It is possible to enable admin-related features for the application by specifying the spring.application.admin.enabled property. This exposes theSpringApplicationAdminMXBean on the platform MBeanServer. You could use this feature to administer your Spring Boot application remotely. This could also be useful for any service wrapper implementation.
| If you want to know on which HTTP port the application is running, get the property with key |
| Take care when enabling this feature as the MBean exposes a method to shutdown the application. |
24. Externalized Configuration
Spring Boot allows you to externalize your configuration so you can work with the same application code in different environments. You can use properties files, YAML files, environment variables and command-line arguments to externalize configuration. Property values can be injected directly into your beans using the @Value annotation, accessed via Spring’s Environment abstraction or bound to structured objects via @ConfigurationProperties.
Spring Boot uses a very particular PropertySource order that is designed to allow sensible overriding of values, properties are considered in the following order:
- Command line arguments.
- Properties from
SPRING_APPLICATION_JSON(inline JSON embedded in an environment variable or system property) - JNDI attributes from
java:comp/env. - Java System properties (
System.getProperties()). - OS environment variables.
- A
RandomValuePropertySourcethat only has properties inrandom.*. - Profile-specific application properties outside of your packaged jar (
application-{profile}.propertiesand YAML variants) - Profile-specific application properties packaged inside your jar (
application-{profile}.propertiesand YAML variants) - Application properties outside of your packaged jar (
application.propertiesand YAML variants). - Application properties packaged inside your jar (
application.propertiesand YAML variants). @PropertySourceannotations on your@Configurationclasses.- Default properties (specified using
SpringApplication.setDefaultProperties).
To provide a concrete example, suppose you develop a @Component that uses a name property:
import org.springframework.stereotype.*
import org.springframework.beans.factory.annotation.*
@Component
public class MyBean {
@Value("${name}")
private String name;
// ...
}On your application classpath (e.g. inside your jar) you can have an application.properties that provides a sensible default property value for name. When running in a new environment, an application.properties can be provided outside of your jar that overrides the name; and for one-off testing, you can launch with a specific command line switch (e.g. java -jar app.jar --name="Spring").
| The In this example you will end up with or command line argument: or as a JNDI variable |
24.1 Configuring random values
The RandomValuePropertySource is useful for injecting random values (e.g. into secrets or test cases). It can produce integers, longs or strings, e.g.
my.secret=${random.value}
my.number=${random.int}
my.bignumber=${random.long}
my.number.less.than.ten=${random.int(10)}
my.number.in.range=${random.int[1024,65536]}The random.int* syntax is OPEN value (,max) CLOSE where the OPEN,CLOSE are any character and value,max are integers. If max is provided then value is the minimum value and max is the maximum (exclusive).
24.2 Accessing command line properties
By default SpringApplication will convert any command line option arguments (starting with ‘--’, e.g. --server.port=9000) to a property and add it to the Spring Environment. As mentioned above, command line properties always take precedence over other property sources.
If you don’t want command line properties to be added to the Environment you can disable them using SpringApplication.setAddCommandLineProperties(false).
24.3 Application property files
SpringApplication will load properties from application.properties files in the following locations and add them to the Spring Environment:
- A
/configsubdirectory of the current directory. - The current directory
- A classpath
/configpackage - The classpath root
The list is ordered by precedence (properties defined in locations higher in the list override those defined in lower locations).
| You can also use YAML ('.yml') files as an alternative to '.properties'. |
If you don’t like application.properties as the configuration file name you can switch to another by specifying a spring.config.name environment property. You can also refer to an explicit location using the spring.config.location environment property (comma-separated list of directory locations, or file paths).
$ java -jar myproject.jar --spring.config.name=myprojector
$ java -jar myproject.jar --spring.config.location=classpath:/default.properties,classpath:/override.properties|
|
If spring.config.location contains directories (as opposed to files) they should end in / (and will be appended with the names generated from spring.config.name before being loaded, including profile-specific file names). Files specified in spring.config.location are used as-is, with no support for profile-specific variants, and will be overridden by any profile-specific properties.
The default search path classpath:,classpath:/config,file:,file:config/ is always used, irrespective of the value of spring.config.location. This search path is ordered from lowest to highest precedence (file:config/ wins). If you do specify your own locations, they take precedence over all of the default locations and use the same lowest to highest precedence ordering. In that way you can set up default values for your application in application.properties (or whatever other basename you choose with spring.config.name) and override it at runtime with a different file, keeping the defaults.
| If you use environment variables rather than system properties, most operating systems disallow period-separated key names, but you can use underscores instead (e.g. |
| If you are running in a container then JNDI properties (in |
24.4 Profile-specific properties
In addition to application.properties files, profile-specific properties can also be defined using the naming convention application-{profile}.properties. The Environment has a set of default profiles (by default [default]) which are used if no active profiles are set (i.e. if no profiles are explicitly activated then properties from application-default.properties are loaded).
Profile-specific properties are loaded from the same locations as standard application.properties, with profile-specific files always overriding the non-specific ones irrespective of whether the profile-specific files are inside or outside your packaged jar.
If several profiles are specified, a last wins strategy applies. For example, profiles specified by the spring.profiles.active property are added after those configured via the SpringApplication API and therefore take precedence.
| If you have specified any files in |
24.5 Placeholders in properties
The values in application.properties are filtered through the existing Environment when they are used so you can refer back to previously defined values (e.g. from System properties).
app.name=MyApp
app.description=${app.name} is a Spring Boot application| You can also use this technique to create ‘short’ variants of existing Spring Boot properties. See the Section 69.3, “Use ‘short’ command line arguments” how-to for details. |
24.6 Using YAML instead of Properties
YAML is a superset of JSON, and as such is a very convenient format for specifying hierarchical configuration data. The SpringApplication class will automatically support YAML as an alternative to properties whenever you have the SnakeYAML library on your classpath.
| If you use ‘starter POMs’ SnakeYAML will be automatically provided via |
24.6.1 Loading YAML
Spring Framework provides two convenient classes that can be used to load YAML documents. The YamlPropertiesFactoryBean will load YAML as Properties and the YamlMapFactoryBean will load YAML as a Map.
For example, the following YAML document:
environments:
dev:
url: http://dev.bar.com
name: Developer Setup
prod:
url: http://foo.bar.com
name: My Cool AppWould be transformed into these properties:
environments.dev.url=http://dev.bar.com
environments.dev.name=Developer Setup
environments.prod.url=http://foo.bar.com
environments.prod.name=My Cool AppYAML lists are represented as property keys with [index] dereferencers, for example this YAML:
my:
servers:
- dev.bar.com
- foo.bar.comWould be transformed into these properties:
my.servers[0]=dev.bar.com
my.servers[1]=foo.bar.comTo bind to properties like that using the Spring DataBinder utilities (which is what @ConfigurationProperties does) you need to have a property in the target bean of type java.util.List (or Set) and you either need to provide a setter, or initialize it with a mutable value, e.g. this will bind to the properties above
@ConfigurationProperties(prefix="my")
public class Config {
private List servers = new ArrayList();
public List getServers() {
return this.servers;
}
} 24.6.2 Exposing YAML as properties in the Spring Environment
The YamlPropertySourceLoader class can be used to expose YAML as a PropertySource in the Spring Environment. This allows you to use the familiar @Value annotation with placeholders syntax to access YAML properties.
24.6.3 Multi-profile YAML documents
You can specify multiple profile-specific YAML documents in a single file by using a spring.profiles key to indicate when the document applies. For example:
server:
address: 192.168.1.100
---
spring:
profiles: development
server:
address: 127.0.0.1
---
spring:
profiles: production
server:
address: 192.168.1.120In the example above, the server.address property will be 127.0.0.1 if the development profile is active. If the development and production profiles are not enabled, then the value for the property will be 192.168.1.100.
The default profiles are activated if none are explicitly active when the application context starts. So in this YAML we set a value for security.user.passwordthat is only available in the "default" profile:
server:
port: 8000
---
spring:
profiles: default
security:
user:
password: weakwhereas in this example, the password is always set because it isn’t attached to any profile, and it would have to be explicitly reset in all other profiles as necessary:
server:
port: 8000
security:
user:
password: weak24.6.4 YAML shortcomings
YAML files can’t be loaded via the @PropertySource annotation. So in the case that you need to load values that way, you need to use a properties file.
24.7 Type-safe Configuration Properties
Using the @Value("${property}") annotation to inject configuration properties can sometimes be cumbersome, especially if you are working with multiple properties or your data is hierarchical in nature. Spring Boot provides an alternative method of working with properties that allows strongly typed beans to govern and validate the configuration of your application. For example:
@Component
@ConfigurationProperties(prefix="connection")
public class ConnectionSettings {
private String username;
private InetAddress remoteAddress;
// ... getters and setters
}| The getters and setters are advisable, since binding is via standard Java Beans property descriptors, just like in Spring MVC. They are mandatory for immutable types or those that are directly coercible from |
| Contrary to |
The @EnableConfigurationProperties annotation is automatically applied to your project so that any beans annotated with @ConfigurationPropertieswill be configured from the Environment properties. This style of configuration works particularly well with the SpringApplication external YAML configuration:
# application.yml
connection:
username: admin
remoteAddress: 192.168.1.1
# additional configuration as requiredTo work with @ConfigurationProperties beans you can just inject them in the same way as any other bean.
@Service
public class MyService {
@Autowired
private ConnectionSettings connection;
//...
@PostConstruct
public void openConnection() {
Server server = new Server();
this.connection.configure(server);
}
}It is also possible to shortcut the registration of @ConfigurationProperties bean definitions by simply listing the properties classes directly in the@EnableConfigurationProperties annotation:
@Configuration
@EnableConfigurationProperties(ConnectionSettings.class)
public class MyConfiguration {
}| Using |
24.7.1 Third-party configuration
As well as using @ConfigurationProperties to annotate a class, you can also use it on @Bean methods. This can be particularly useful when you want to bind properties to third-party components that are outside of your control.
To configure a bean from the Environment properties, add @ConfigurationProperties to its bean registration:
@ConfigurationProperties(prefix = "foo")
@Bean
public FooComponent fooComponent() {
...
}Any property defined with the foo prefix will be mapped onto that FooComponent bean in a similar manner as the ConnectionSettings example above.
24.7.2 Relaxed binding
Spring Boot uses some relaxed rules for binding Environment properties to @ConfigurationProperties beans, so there doesn’t need to be an exact match between the Environment property name and the bean property name. Common examples where this is useful include dashed separated (e.g. context-path binds to contextPath), and capitalized (e.g. PORT binds to port) environment properties.
For example, given the following @ConfigurationProperties class:
@Component
@ConfigurationProperties(prefix="person")
public class ConnectionSettings {
private String firstName;
public String getFirstName() {
return this.firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
}The following properties names can all be used:
Table 24.1. relaxed binding
| Property | Note |
|---|---|
|
|
Standard camel case syntax. |
|
|
Dashed notation, recommended for use in |
|
|
Underscore notation, alternative format for use in |
|
|
Upper case format. Recommended when using a system environment variables. |
24.7.3 Properties conversion
Spring will attempt to coerce the external application properties to the right type when it binds to the @ConfigurationProperties beans. If you need custom type conversion you can provide a ConversionService bean (with bean id conversionService) or custom property editors (via a CustomEditorConfigurer bean) or custom Converters (with bean definitions annotated as @ConfigurationPropertiesBinding).
| As this bean is requested very early during the application lifecycle, make sure to limit the dependencies that your |
24.7.4 @ConfigurationProperties Validation
Spring Boot will attempt to validate external configuration, by default using JSR-303 (if it is on the classpath). You can simply add JSR-303 javax.validationconstraint annotations to your @ConfigurationProperties class:
@Component
@ConfigurationProperties(prefix="connection")
public class ConnectionSettings {
@NotNull
private InetAddress remoteAddress;
// ... getters and setters
}In order to validate values of nested properties, you must annotate the associated field as @Valid to trigger its validation. For example, building upon the above ConnectionSettings example:
@Component
@ConfigurationProperties(prefix="connection")
public class ConnectionSettings {
@NotNull
@Valid
private RemoteAddress remoteAddress;
// ... getters and setters
public static class RemoteAddress {
@NotEmpty
public String hostname;
// ... getters and setters
}
}You can also add a custom Spring Validator by creating a bean definition called configurationPropertiesValidator. There is a Validation sample so you can see how to set things up.
| The |
25. Profiles
Spring Profiles provide a way to segregate parts of your application configuration and make it only available in certain environments. Any @Component or @Configuration can be marked with @Profile to limit when it is loaded:
@Configuration
@Profile("production")
public class ProductionConfiguration {
// ...
}In the normal Spring way, you can use a spring.profiles.active Environment property to specify which profiles are active. You can specify the property in any of the usual ways, for example you could include it in your application.properties:
spring.profiles.active=dev,hsqldbor specify on the command line using the switch --spring.profiles.active=dev,hsqldb.
25.1 Adding active profiles
The spring.profiles.active property follows the same ordering rules as other properties, the highest PropertySource will win. This means that you can specify active profiles in application.properties then replace them using the command line switch.
Sometimes it is useful to have profile-specific properties that add to the active profiles rather than replace them. The spring.profiles.include property can be used to unconditionally add active profiles. The SpringApplication entry point also has a Java API for setting additional profiles (i.e. on top of those activated by the spring.profiles.active property): see the setAdditionalProfiles() method.
For example, when an application with following properties is run using the switch --spring.profiles.active=prod the proddb and prodmq profiles will also be activated:
---
my.property: fromyamlfile
---
spring.profiles: prod
spring.profiles.include: proddb,prodmq| Remember that the |
25.2 Programmatically setting profiles
You can programmatically set active profiles by calling SpringApplication.setAdditionalProfiles(…) before your application runs. It is also possible to activate profiles using Spring’s ConfigurableEnvironment interface.
25.3 Profile-specific configuration files
Profile-specific variants of both application.properties (or application.yml) and files referenced via @ConfigurationProperties are considered as files are loaded. See Section 24.4, “Profile-specific properties” for details.
26. Logging
Spring Boot uses Commons Logging for all internal logging, but leaves the underlying log implementation open. Default configurations are provided for Java Util Logging, Log4J, Log4J2 and Logback. In each case loggers are pre-configured to use console output with optional file output also available.
By default, If you use the ‘Starter POMs’, Logback will be used for logging. Appropriate Logback routing is also included to ensure that dependent libraries that use Java Util Logging, Commons Logging, Log4J or SLF4J will all work correctly.
| There are a lot of logging frameworks available for Java. Don’t worry if the above list seems confusing. Generally you won’t need to change your logging dependencies and the Spring Boot defaults will work just fine. |
26.1 Log format
The default log output from Spring Boot looks like this:
2014-03-05 10:57:51.112 INFO 45469 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet Engine: Apache Tomcat/7.0.52
2014-03-05 10:57:51.253 INFO 45469 --- [ost-startStop-1] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext
2014-03-05 10:57:51.253 INFO 45469 --- [ost-startStop-1] o.s.web.context.ContextLoader : Root WebApplicationContext: initialization completed in 1358 ms
2014-03-05 10:57:51.698 INFO 45469 --- [ost-startStop-1] o.s.b.c.e.ServletRegistrationBean : Mapping servlet: 'dispatcherServlet' to [/]
2014-03-05 10:57:51.702 INFO 45469 --- [ost-startStop-1] o.s.b.c.embedded.FilterRegistrationBean : Mapping filter: 'hiddenHttpMethodFilter' to: [/*]The following items are output:
- Date and Time — Millisecond precision and easily sortable.
- Log Level —
ERROR,WARN,INFO,DEBUGorTRACE. - Process ID.
- A
---separator to distinguish the start of actual log messages. - Thread name — Enclosed in square brackets (may be truncated for console output).
- Logger name — This is usually the source class name (often abbreviated).
- The log message.
| Logback does not have a |
26.2 Console output
The default log configuration will echo messages to the console as they are written. By default ERROR, WARN and INFO level messages are logged. You can also enable a “debug” mode by starting your application with a --debug flag.
$ java -jar myapp.jar --debug| you can also specify |
When the debug mode is enabled, a selection of core loggers (embedded container, Hibernate and Spring) are configured to output more information. Enabling the debug mode does not configure your application log all messages with DEBUG level.
26.2.1 Color-coded output
If your terminal supports ANSI, color output will be used to aid readability. You can set spring.output.ansi.enabled to a supported value to override the auto detection.
Color coding is configured using the %clr conversion word. In its simplest form the converter will color the output according to the log level, for example:
%clr(%5p)The mapping of log level to a color is as follows:
| Level | Color |
|---|---|
|
|
Red |
|
|
Red |
|
|
Yellow |
|
|
Green |
|
|
Green |
|
|
Green |
Alternatively, you can specify the color or style that should be used by providing it as an option to the conversion. For example, to make the text yellow:
%clr(%d{yyyy-MM-dd HH:mm:ss.SSS}){yellow}The following colors and styles are supported:
bluecyanfaintgreenmagentaredyellow
26.3 File output
By default, Spring Boot will only log to the console and will not write log files. If you want to write log files in addition to the console output you need to set alogging.file or logging.path property (for example in your application.properties).
The following table shows how the logging.* properties can be used together:
Table 26.1. Logging properties
logging.file |
logging.path |
Example | Description |
|---|---|---|---|
| (none) |
(none) |
Console only logging. |
|
| Specific file |
(none) |
|
Writes to the specified log file. Names can be an exact location or relative to the current directory. |
| (none) |
Specific directory |
|
Writes |
Log files will rotate when they reach 10 Mb and as with console output, ERROR, WARN and INFO level messages are logged by default.
| The logging system is initialized early in the application lifecycle and as such logging properties will not be found in property files loaded via |
| Logging properties are independent of the actual logging infrastructure. As a result, specific configuration keys (such as |
26.4 Log Levels
All the supported logging systems can have the logger levels set in the Spring Environment (so for example in application.properties) using ‘logging.level.*=LEVEL’ where ‘LEVEL’ is one of TRACE, DEBUG, INFO, WARN, ERROR, FATAL, OFF. The root logger can be configured using logging.level.root. Example application.properties:
logging.level.root=WARN
logging.level.org.springframework.web=DEBUG
logging.level.org.hibernate=ERROR| By default Spring Boot remaps Thymeleaf |
26.5 Custom log configuration
The various logging systems can be activated by including the appropriate libraries on the classpath, and further customized by providing a suitable configuration file in the root of the classpath, or in a location specified by the Spring Environment property logging.config.
| Since logging is initialized before the |
Depending on your logging system, the following files will be loaded:
| Logging System | Customization |
|---|---|
| Logback |
|
| Log4j |
|
| Log4j2 |
|
| JDK (Java Util Logging) |
|
| When possible we recommend that you use the |
| There are known classloading issues with Java Util Logging that cause problems when running from an ‘executable jar’. We recommend that you avoid it if at all possible. |
To help with the customization some other properties are transferred from the Spring Environment to System properties:
| Spring Environment | System Property | Comments |
|---|---|---|
|
|
|
The conversion word that’s used when logging exceptions. |
|
|
|
Used in default log configuration if defined. |
|
|
|
Used in default log configuration if defined. |
|
|
|
The log pattern to use on the console (stdout). (Only supported with the default logback setup.) |
|
|
|
The log pattern to use in a file (if LOG_FILE enabled). (Only supported with the default logback setup.) |
|
|
|
The format to use to render the log level (default |
|
|
|
The current process ID (discovered if possible and when not already defined as an OS environment variable). |
All the logging systems supported can consult System properties when parsing their configuration files. See the default configurations in spring-boot.jar for examples.
| If you want to use a placeholder in a logging property, you should use Spring Boot’s syntax and not the syntax of the underlying framework. Notably, if you’re using Logback, you should use |
| You can add MDC and other ad-hoc content to log lines by overriding only the |
26.6 Logback extensions
Spring Boot includes a number of extensions to Logback which can help with advanced configuration. You can use these extensions in your logback-spring.xml configuration file.
| You cannot use extensions in the standard |
26.6.1 Profile-specific configuration
The name attribute to specify which profile accepts the configuration. Multiple profiles can be specified using a comma-separated list.
name="staging">
name="dev, staging">
name="!production">
26.6.2 Environment properties
The Environment for use within Logback. This can be useful if you want to access values from your application.properties file in your logback configuration. The tag works in a similar way to Logback’s standard value you specify the source of the property (from the Environment). You can use the scope attribute if you need to store the property somewhere other than in local scope.
scope="context" name="fluentHost" source="myapp.fluentd.host"/>
name="FLUENT" class="ch.qos.logback.more.appenders.DataFluentAppender">
| The |
27. Developing web applications
Spring Boot is well suited for web application development. You can easily create a self-contained HTTP server using embedded Tomcat, Jetty, or Undertow. Most web applications will use the spring-boot-starter-web module to get up and running quickly.
If you haven’t yet developed a Spring Boot web application you can follow the "Hello World!" example in the Getting started section.
27.1 The ‘Spring Web MVC framework’
The Spring Web MVC framework (often referred to as simply ‘Spring MVC’) is a rich ‘model view controller’ web framework. Spring MVC lets you create special @Controller or @RestController beans to handle incoming HTTP requests. Methods in your controller are mapped to HTTP using @RequestMappingannotations.
Here is a typical example @RestController to serve JSON data:
@RestController
@RequestMapping(value="/users")
public class MyRestController {
@RequestMapping(value="/{user}", method=RequestMethod.GET)
public User getUser(@PathVariable Long user) {
// ...
}
@RequestMapping(value="/{user}/customers", method=RequestMethod.GET)
List getUserCustomers(@PathVariable Long user) {
// ...
}
@RequestMapping(value="/{user}", method=RequestMethod.DELETE)
public User deleteUser(@PathVariable Long user) {
// ...
}
} Spring MVC is part of the core Spring Framework and detailed information is available in the reference documentation. There are also several guides available at spring.io/guides that cover Spring MVC.
27.1.1 Spring MVC auto-configuration
Spring Boot provides auto-configuration for Spring MVC that works well with most applications.
The auto-configuration adds the following features on top of Spring’s defaults:
- Inclusion of
ContentNegotiatingViewResolverandBeanNameViewResolverbeans. - Support for serving static resources, including support for WebJars (see below).
- Automatic registration of
Converter,GenericConverter,Formatterbeans. - Support for
HttpMessageConverters(see below). - Automatic registration of
MessageCodesResolver(see below). - Static
index.htmlsupport. - Custom
Faviconsupport. - Automatic use of a
ConfigurableWebBindingInitializerbean (see below).
If you want to take complete control of Spring MVC, you can add your own @Configuration annotated with @EnableWebMvc. If you want to keep Spring Boot MVC features, and you just want to add additional MVC configuration (interceptors, formatters, view controllers etc.) you can add your own @Bean of typeWebMvcConfigurerAdapter, but without @EnableWebMvc.
27.1.2 HttpMessageConverters
Spring MVC uses the HttpMessageConverter interface to convert HTTP requests and responses. Sensible defaults are included out of the box, for example Objects can be automatically converted to JSON (using the Jackson library) or XML (using the Jackson XML extension if available, else using JAXB). Strings are encoded using UTF-8 by default.
If you need to add or customize converters you can use Spring Boot’s HttpMessageConverters class:
import org.springframework.boot.autoconfigure.web.HttpMessageConverters;
import org.springframework.context.annotation.*;
import org.springframework.http.converter.*;
@Configuration
public class MyConfiguration {
@Bean
public HttpMessageConverters customConverters() {
HttpMessageConverter additional = ...
HttpMessageConverter another = ...
return new HttpMessageConverters(additional, another);
}
}Any HttpMessageConverter bean that is present in the context will be added to the list of converters. You can also override default converters that way.
27.1.3 MessageCodesResolver
Spring MVC has a strategy for generating error codes for rendering error messages from binding errors: MessageCodesResolver. Spring Boot will create one for you if you set the spring.mvc.message-codes-resolver.format property PREFIX_ERROR_CODE or POSTFIX_ERROR_CODE (see the enumeration in DefaultMessageCodesResolver.Format).
27.1.4 Static Content
By default Spring Boot will serve static content from a directory called /static (or /public or /resources or /META-INF/resources) in the classpath or from the root of the ServletContext. It uses the ResourceHttpRequestHandler from Spring MVC so you can modify that behavior by adding your own WebMvcConfigurerAdapter and overriding the addResourceHandlers method.
In a stand-alone web application the default servlet from the container is also enabled, and acts as a fallback, serving content from the root of the ServletContext if Spring decides not to handle it. Most of the time this will not happen (unless you modify the default MVC configuration) because Spring will always be able to handle requests through the DispatcherServlet.
You can customize the static resource locations using spring.resources.staticLocations (replacing the default values with a list of directory locations). If you do this the default welcome page detection will switch to your custom locations, so if there is an index.html in any of your locations on startup, it will be the home page of the application.
In addition to the ‘standard’ static resource locations above, a special case is made for Webjars content. Any resources with a path in /webjars/** will be served from jar files if they are packaged in the Webjars format.
| Do not use the |
Spring Boot also supports advanced resource handling features provided by Spring MVC, allowing use cases such as cache busting static resources or using version agnostic URLs for Webjars.
For example, the following configuration will configure a cache busting solution for all static resources, effectively adding a content hash in URLs, such as:
spring.resources.chain.strategy.content.enabled=true
spring.resources.chain.strategy.content.paths=/**| Links to resources are rewritten at runtime in template, thanks to a |
When loading resources dynamically with, for example, a JavaScript module loader, renaming files is not an option. That’s why other strategies are also supported and can be combined. A "fixed" strategy will add a static version string in the URL, without changing the file name:
spring.resources.chain.strategy.content.enabled=true
spring.resources.chain.strategy.content.paths=/**
spring.resources.chain.strategy.fixed.enabled=true
spring.resources.chain.strategy.fixed.paths=/js/lib/
spring.resources.chain.strategy.fixed.version=v12With this configuration, JavaScript modules located under "/js/lib/" will use a fixed versioning strategy "/v12/js/lib/mymodule.js" while other resources will still use the content one .
See ResourceProperties for more of the supported options.
| This feature has been thoroughly described in a dedicated blog post and in Spring Framework’s reference documentation. |
27.1.5 ConfigurableWebBindingInitializer
Spring MVC uses a WebBindingInitializer to initialize a WebDataBinder for a particular request. If you create your own ConfigurableWebBindingInitializer @Bean, Spring Boot will automatically configure Spring MVC to use it.
27.1.6 Template engines
As well as REST web services, you can also use Spring MVC to serve dynamic HTML content. Spring MVC supports a variety of templating technologies including Velocity, FreeMarker and JSPs. Many other templating engines also ship their own Spring MVC integrations.
Spring Boot includes auto-configuration support for the following templating engines:
- FreeMarker
- Groovy
- Thymeleaf
- Velocity
- Mustache
| JSPs should be avoided if possible, there are several known limitations when using them with embedded servlet containers. |
When you’re using one of these templating engines with the default configuration, your templates will be picked up automatically from src/main/resources/templates.
| IntelliJ IDEA orders the classpath differently depending on how you run your application. Running your application in the IDE via its main method will result in a different ordering to when you run your application using Maven or Gradle or from its packaged jar. This can cause Spring Boot to fail to find the templates on the classpath. If you’re affected by this problem you can reorder the classpath in the IDE to place the module’s classes and resources first. Alternatively, you can configure the template prefix to search every templates directory on the classpath: |
27.1.7 Error Handling
Spring Boot provides an /error mapping by default that handles all errors in a sensible way, and it is registered as a ‘global’ error page in the servlet container. For machine clients it will produce a JSON response with details of the error, the HTTP status and the exception message. For browser clients there is a ‘whitelabel’ error view that renders the same data in HTML format (to customize it just add a View that resolves to ‘error’). To replace the default behaviour completely you can implement ErrorController and register a bean definition of that type, or simply add a bean of type ErrorAttributes to use the existing mechanism but replace the contents.
| The |
You can also define a @ControllerAdvice to customize the JSON document to return for a particular controller and/or exception type.
@ControllerAdvice(basePackageClasses = FooController.class)
public class FooControllerAdvice extends ResponseEntityExceptionHandler {
@ExceptionHandler(YourException.class)
@ResponseBody
ResponseEntity handleControllerException(HttpServletRequest request, Throwable ex) {
HttpStatus status = getStatus(request);
return new ResponseEntity<>(new CustomErrorType(status.value(), ex.getMessage()), status);
}
private HttpStatus getStatus(HttpServletRequest request) {
Integer statusCode = (Integer) request.getAttribute("javax.servlet.error.status_code");
if (statusCode == null) {
return HttpStatus.INTERNAL_SERVER_ERROR;
}
return HttpStatus.valueOf(statusCode);
}
}In the example above, if YourException is thrown by a controller defined in the same package as FooController, a json representation of the CustomerErrorType POJO will be used instead of the ErrorAttributes representation.
If you want more specific error pages for some conditions, the embedded servlet containers support a uniform Java DSL for customizing the error handling. Assuming that you have a mapping for /400:
@Bean
public EmbeddedServletContainerCustomizer containerCustomizer(){
return new MyCustomizer();
}
// ...
private static class MyCustomizer implements EmbeddedServletContainerCustomizer {
@Override
public void customize(ConfigurableEmbeddedServletContainer container) {
container.addErrorPages(new ErrorPage(HttpStatus.BAD_REQUEST, "/400"));
}
}You can also use regular Spring MVC features like @ExceptionHandler methods and @ControllerAdvice. The ErrorController will then pick up any unhandled exceptions.
N.B. if you register an ErrorPage with a path that will end up being handled by a Filter (e.g. as is common with some non-Spring web frameworks, like Jersey and Wicket), then the Filter has to be explicitly registered as an ERROR dispatcher, e.g.
@Bean
public FilterRegistrationBean myFilter() {
FilterRegistrationBean registration = new FilterRegistrationBean();
registration.setFilter(new MyFilter());
...
registration.setDispatcherTypes(EnumSet.allOf(DispatcherType.class));
return registration;
}(the default FilterRegistrationBean does not include the ERROR dispatcher type).
Error Handling on WebSphere Application Server
When deployed to a servlet container, a Spring Boot uses its error page filter to forward a request with an error status to the appropriate error page. The request can only be forwarded to the correct error page if the response has not already been committed. By default, WebSphere Application Server 8.0 and later commits the response upon successful completion of a servlet’s service method. You should disable this behaviour by settingcom.ibm.ws.webcontainer.invokeFlushAfterService to false
27.1.8 Spring HATEOAS
If you’re developing a RESTful API that makes use of hypermedia, Spring Boot provides auto-configuration for Spring HATEOAS that works well with most applications. The auto-configuration replaces the need to use @EnableHypermediaSupport and registers a number of beans to ease building hypermedia-based applications including a LinkDiscoverers (for client side support) and an ObjectMapper configured to correctly marshal responses into the desired representation. The ObjectMapper will be customized based on the spring.jackson.* properties or a Jackson2ObjectMapperBuilder bean if one exists.
You can take control of Spring HATEOAS’s configuration by using @EnableHypermediaSupport. Note that this will disable the ObjectMapper customization described above.
27.1.9 CORS support
Cross-origin resource sharing (CORS) is a W3C specification implemented by most browsers that allows you to specify in a flexible way what kind of cross domain requests are authorized, instead of using some less secure and less powerful approaches like IFRAME or JSONP.
As of version 4.2, Spring MVC supports CORS out of the box. Using controller method CORS configuration with @CrossOrigin annotations in your Spring Boot application does not require any specific configuration. Global CORS configuration can be defined by registering a WebMvcConfigurer bean with a customized addCorsMappings(CorsRegistry) method:
@Configuration
public class MyConfiguration {
@Bean
public WebMvcConfigurer corsConfigurer() {
return new WebMvcConfigurerAdapter() {
@Override
public void addCorsMappings(CorsRegistry registry) {
registry.addMapping("/api/**");
}
};
}
}27.2 JAX-RS and Jersey
If you prefer the JAX-RS programming model for REST endpoints you can use one of the available implementations instead of Spring MVC. Jersey 1.x and Apache CXF work quite well out of the box if you just register their Servlet or Filter as a @Bean in your application context. Jersey 2.x has some native Spring support so we also provide auto-configuration support for it in Spring Boot together with a starter.
To get started with Jersey 2.x just include the spring-boot-starter-jersey as a dependency and then you need one @Bean of type ResourceConfig in which you register all the endpoints:
@Component
public class JerseyConfig extends ResourceConfig {
public JerseyConfig() {
register(Endpoint.class);
}
}All the registered endpoints should be @Components with HTTP resource annotations (@GET etc.), e.g.
@Component
@Path("/hello")
public class Endpoint {
@GET
public String message() {
return "Hello";
}
}Since the Endpoint is a Spring @Component its lifecycle is managed by Spring and you can @Autowired dependencies and inject external configuration with @Value. The Jersey servlet will be registered and mapped to /* by default. You can change the mapping by adding @ApplicationPath to your ResourceConfig.
By default Jersey will be set up as a Servlet in a @Bean of type ServletRegistrationBean named jerseyServletRegistration. You can disable or override that bean by creating one of your own with the same name. You can also use a Filter instead of a Servlet by setting spring.jersey.type=filter (in which case the @Bean to replace or override is jerseyFilterRegistration). The servlet has an @Order which you can set with spring.jersey.filter.order. Both the Servlet and the Filter registrations can be given init parameters using spring.jersey.init.* to specify a map of properties.
There is a Jersey sample so you can see how to set things up. There is also a Jersey 1.x sample. Note that in the Jersey 1.x sample that the spring-boot maven plugin has been configured to unpack some Jersey jars so they can be scanned by the JAX-RS implementation (because the sample asks for them to be scanned in its Filter registration). You may need to do the same if any of your JAX-RS resources are packaged as nested jars.
27.3 Embedded servlet container support
Spring Boot includes support for embedded Tomcat, Jetty, and Undertow servers. Most developers will simply use the appropriate ‘Starter POM’ to obtain a fully configured instance. By default the embedded server will listen for HTTP requests on port 8080.
27.3.1 Servlets, Filters, and listeners
When using an embedded servlet container you can register Servlets, Filters and all the listeners from the Servlet spec (e.g. HttpSessionListener) either by using Spring beans or by scanning for Servlet components.
Registering Servlets, Filters, and listeners as Spring beans
Any Servlet, Filter or Servlet *Listener instance that is a Spring bean will be registered with the embedded container. This can be particularly convenient if you want to refer to a value from your application.properties during configuration.
By default, if the context contains only a single Servlet it will be mapped to /. In the case of multiple Servlet beans the bean name will be used as a path prefix. Filters will map to /*.
If convention-based mapping is not flexible enough you can use the ServletRegistrationBean, FilterRegistrationBean and ServletListenerRegistrationBean classes for complete control.
27.3.2 Servlet Context Initialization
Embedded servlet containers will not directly execute the Servlet 3.0+ javax.servlet.ServletContainerInitializer interface, or Spring’sorg.springframework.web.WebApplicationInitializer interface. This is an intentional design decision intended to reduce the risk that 3rd party libraries designed to run inside a war will break Spring Boot applications.
If you need to perform servlet context initialization in a Spring Boot application, you should register a bean that implements theorg.springframework.boot.context.embedded.ServletContextInitializer interface. The single onStartup method provides access to the ServletContext, and can easily be used as an adapter to an existing WebApplicationInitializer if necessary.
Scanning for Servlets, Filters, and listeners
When using an embedded container, automatic registration of @WebServlet, @WebFilter, and @WebListener annotated classes can be enabled using @ServletComponentScan.
|
|
27.3.3 The EmbeddedWebApplicationContext
Under the hood Spring Boot uses a new type of ApplicationContext for embedded servlet container support. The EmbeddedWebApplicationContext is a special type of WebApplicationContext that bootstraps itself by searching for a single EmbeddedServletContainerFactory bean. Usually a TomcatEmbeddedServletContainerFactory, JettyEmbeddedServletContainerFactory, or UndertowEmbeddedServletContainerFactory will have been auto-configured.
| You usually won’t need to be aware of these implementation classes. Most applications will be auto-configured and the appropriate |
27.3.4 Customizing embedded servlet containers
Common servlet container settings can be configured using Spring Environment properties. Usually you would define the properties in your application.properties file.
Common server settings include:
- Network settings: listen port for incoming HTTP requests (
server.port), interface address to bind toserver.address, etc. - Session settings: whether the session is persistent (
server.session.persistence), session timeout (server.session.timeout), location of session data (server.session.store-dir) and session-cookie configuration (server.session.cookie.*). - Error management: location of the error page (
server.error.path), etc. - SSL
- HTTP compression
Spring Boot tries as much as possible to expose common settings but this is not always possible. For those cases, dedicated namespaces offer server-specific customizations (see server.tomcat and server.undertow). For instance, access logs can be configured with specific features of the embedded servlet container.
| See the |
Programmatic customization
If you need to configure your embedded servlet container programmatically you can register a Spring bean that implements the EmbeddedServletContainerCustomizer interface. EmbeddedServletContainerCustomizer provides access to theConfigurableEmbeddedServletContainer which includes numerous customization setter methods.
import org.springframework.boot.context.embedded.*;
import org.springframework.stereotype.Component;
@Component
public class CustomizationBean implements EmbeddedServletContainerCustomizer {
@Override
public void customize(ConfigurableEmbeddedServletContainer container) {
container.setPort(9000);
}
}Customizing ConfigurableEmbeddedServletContainer directly
If the above customization techniques are too limited, you can register the TomcatEmbeddedServletContainerFactory, JettyEmbeddedServletContainerFactory or UndertowEmbeddedServletContainerFactory bean yourself.
@Bean
public EmbeddedServletContainerFactory servletContainer() {
TomcatEmbeddedServletContainerFactory factory = new TomcatEmbeddedServletContainerFactory();
factory.setPort(9000);
factory.setSessionTimeout(10, TimeUnit.MINUTES);
factory.addErrorPages(new ErrorPage(HttpStatus.NOT_FOUND, "/notfound.html"));
return factory;
}Setters are provided for many configuration options. Several protected method ‘hooks’ are also provided should you need to do something more exotic. See the source code documentation for details.
27.3.5 JSP limitations
When running a Spring Boot application that uses an embedded servlet container (and is packaged as an executable archive), there are some limitations in the JSP support.
- With Tomcat it should work if you use war packaging, i.e. an executable war will work, and will also be deployable to a standard container (not limited to, but including Tomcat). An executable jar will not work because of a hard coded file pattern in Tomcat.
- Jetty does not currently work as an embedded container with JSPs.
- Undertow does not support JSPs.
- Creating a custom
error.jsppage won’t override the default view for error handling.
There is a JSP sample so you can see how to set things up.
28. Security
If Spring Security is on the classpath then web applications will be secure by default with ‘basic’ authentication on all HTTP endpoints. To add method-level security to a web application you can also add @EnableGlobalMethodSecurity with your desired settings. Additional information can be found in the Spring Security Reference.
The default AuthenticationManager has a single user (‘user’ username and random password, printed at INFO level when the application starts up)
Using default security password: 78fa095d-3f4c-48b1-ad50-e24c31d5cf35| If you fine tune your logging configuration, ensure that the |
You can change the password by providing a security.user.password. This and other useful properties are externalized via SecurityProperties(properties prefix "security").
The default security configuration is implemented in SecurityAutoConfiguration and in the classes imported from there (SpringBootWebSecurityConfiguration for web security and AuthenticationManagerConfiguration for authentication configuration which is also relevant in non-web applications). To switch off the default web security configuration completely you can add a bean with @EnableWebSecurity (this does not disable the authentication manager configuration). To customize it you normally use external properties and beans of type WebSecurityConfigurerAdapter(e.g. to add form-based login). To also switch off the authentication manager configuration you can add a bean of type AuthenticationManager, or else configure the global AuthenticationManager by autowiring an AuthenticationManagerBuilder into a method in one of your @Configuration classes. There are several secure applications in the Spring Boot samples to get you started with common use cases.
The basic features you get out of the box in a web application are:
- An
AuthenticationManagerbean with in-memory store and a single user (seeSecurityProperties.Userfor the properties of the user). - Ignored (insecure) paths for common static resource locations (
/css/**,/js/**,/images/**and**/favicon.ico). - HTTP Basic security for all other endpoints.
- Security events published to Spring’s
ApplicationEventPublisher(successful and unsuccessful authentication and access denied). - Common low-level features (HSTS, XSS, CSRF, caching) provided by Spring Security are on by default.
All of the above can be switched on and off or modified using external properties (security.*). To override the access rules without changing any other auto-configured features add a @Bean of type WebSecurityConfigurerAdapter with @Order(SecurityProperties.ACCESS_OVERRIDE_ORDER) and configure it to meet your needs.
| By default, a |
28.1 OAuth2
If you have spring-security-oauth2 on your classpath you can take advantage of some auto-configuration to make it easy to set up Authorization or Resource Server.
28.1.1 Authorization Server
To create an Authorization Server and grant access tokens you need to use @EnableAuthorizationServer and provide security.oauth2.client.client-id and security.oauth2.client.client-secret] properties. The client will be registered for you in an in-memory repository.
Having done that you will be able to use the client credentials to create an access token, for example:
$ curl client:secret@localhost:8080/oauth/token -d grant_type=password -d username=user -d password=pwdThe basic auth credentials for the /token endpoint are the client-id and client-secret. The user credentials are the normal Spring Security user details (which default in Spring Boot to “user” and a random password).
To switch off the auto-configuration and configure the Authorization Server features yourself just add a @Bean of type AuthorizationServerConfigurer.
28.1.2 Resource Server
To use the access token you need a Resource Server (which can be the same as the Authorization Server). Creating a Resource Server is easy, just add@EnableResourceServer and provide some configuration to allow the server to decode access tokens. If your application is also an Authorization Server it already knows how to decode tokens, so there is nothing else to do. If your app is a standalone service then you need to give it some more configuration, one of the following options:
security.oauth2.resource.user-info-urito use the/meresource (e.g.uaa.run.pivotal.io/userinfoon PWS)security.oauth2.resource.token-info-urito use the token decoding endpoint (e.g.uaa.run.pivotal.io/check_tokenon PWS).
If you specify both the user-info-uri and the token-info-uri then you can set a flag to say that one is preferred over the other (prefer-token-info=true is the default).
Alternatively (instead of user-info-uri or token-info-uri) if the tokens are JWTs you can configure a security.oauth2.resource.jwt.key-value to decode them locally (where the key is a verification key). The verification key value is either a symmetric secret or PEM-encoded RSA public key. If you don’t have the key and it’s public you can provide a URI where it can be downloaded (as a JSON object with a “value” field) withsecurity.oauth2.resource.jwt.key-uri. E.g. on PWS:
$ curl https://uaa.run.pivotal.io/token_key
{"alg":"SHA256withRSA","value":"-----BEGIN PUBLIC KEY-----\nMIIBI...\n-----END PUBLIC KEY-----\n"}| If you use the |
28.2 Token Type in User Info
Google, and certain other 3rd party identity providers, are more strict about the token type name that is sent in the headers to the user info endpoint. The default is “Bearer” which suits most providers and matches the spec, but if you need to change it you can set security.oauth2.resource.token-type.
28.3 Customizing the User Info RestTemplate
If you have a user-info-uri, the resource server features use an OAuth2RestTemplate internally to fetch user details for authentication. This is provided as a qualified @Bean with id userInfoRestTemplate, but you shouldn’t need to know that to just use it. The default should be fine for most providers, but occasionally you might need to add additional interceptors, or change the request authenticator (which is how the token gets attached to outgoing requests). To add a customization just create a bean of type UserInfoRestTemplateCustomizer - it has a single method that will be called after the bean is created but before it is initialized. The rest template that is being customized here is only used internally to carry out authentication.
| To set an RSA key value in YAML use the “pipe” continuation marker to split it over multiple lines (“|”) and remember to indent the key value (it’s a standard YAML language feature). Example: |
28.3.1 Client
To make your webapp into an OAuth2 client you can simply add @EnableOAuth2Client and Spring Boot will create an OAuth2RestTemplate for you to @Autowire. It uses the security.oauth2.client.* as credentials (the same as you might be using in the Authorization Server), but in addition it will need to know the authorization and token URIs in the Authorization Server. For example:
application.yml.
security:
oauth2:
client:
clientId: bd1c0a783ccdd1c9b9e4
clientSecret: 1a9030fbca47a5b2c28e92f19050bb77824b5ad1
accessTokenUri: https://github.com/login/oauth/access_token
userAuthorizationUri: https://github.com/login/oauth/authorize
clientAuthenticationScheme: form
An application with this configuration will redirect to Github for authorization when you attempt to use the OAuth2RestTemplate. If you are already signed into Github you won’t even notice that it has authenticated. These specific credentials will only work if your application is running on port 8080 (register your own client app in Github or other provider for more flexibility).
To limit the scope that the client asks for when it obtains an access token you can set security.oauth2.client.scope (comma separated or an array in YAML). By default the scope is empty and it is up to Authorization Server to decide what the defaults should be, usually depending on the settings in the client registration that it holds.
| There is also a setting for |
| In a non-web application you can still |
28.3.2 Single Sign On
An OAuth2 Client can be used to fetch user details from the provider (if such features are available) and then convert them into an Authentication token for Spring Security. The Resource Server above support this via the user-info-uri property This is the basis for a Single Sign On (SSO) protocol based on OAuth2, and Spring Boot makes it easy to participate by providing an annotation @EnableOAuth2Sso. The Github client above can protect all its resources and authenticate using the Github /user/ endpoint, by adding that annotation and declaring where to find the endpoint (in addition to thesecurity.oauth2.client.* configuration already listed above):
application.yml.
security:
oauth2:
...
resource:
userInfoUri: https://api.github.com/user
preferTokenInfo: false
Since all paths are secure by default, there is no “home” page that you can show to unauthenticated users and invite them to login (by visiting the /login path, or the path specified by security.oauth2.sso.login-path).
To customize the access rules or paths to protect, so you can add a “home” page for instance, @EnableOAuth2Sso can be added to a WebSecurityConfigurerAdapter and the annotation will cause it to be decorated and enhanced with the necessary pieces to get the /login path working. For example, here we simply allow unauthenticated access to the home page at "/" and keep the default for everything else:
@Configuration
public class WebSecurityConfiguration extends WebSecurityConfigurerAdapter {
@Override
public void init(WebSecurity web) {
web.ignore("/");
}
@Override
protected void configure(HttpSecurity http) throws Exception {
http.antMatcher("/**").authorizeRequests().anyRequest().authenticated();
}
}28.4 Actuator Security
If the Actuator is also in use, you will find:
- The management endpoints are secure even if the application endpoints are insecure.
- Security events are transformed into
AuditEventsand published to theAuditService. - The default user will have the
ADMINrole as well as theUSERrole.
The Actuator security features can be modified using external properties (management.security.*). To override the application access rules add a @Bean of type WebSecurityConfigurerAdapter and use @Order(SecurityProperties.ACCESS_OVERRIDE_ORDER) if you don’t want to override the actuator access rules, or @Order(ManagementServerProperties.ACCESS_OVERRIDE_ORDER) if you do want to override the actuator access rules.
29. Working with SQL databases
The Spring Framework provides extensive support for working with SQL databases. From direct JDBC access using JdbcTemplate to complete ‘object relational mapping’ technologies such as Hibernate. Spring Data provides an additional level of functionality, creating Repository implementations directly from interfaces and using conventions to generate queries from your method names.
29.1 Configure a DataSource
Java’s javax.sql.DataSource interface provides a standard method of working with database connections. Traditionally a DataSource uses a URL along with some credentials to establish a database connection.
29.1.1 Embedded Database Support
It’s often convenient to develop applications using an in-memory embedded database. Obviously, in-memory databases do not provide persistent storage; you will need to populate your database when your application starts and be prepared to throw away data when your application ends.
| The ‘How-to’ section includes a section on how to initialize a database |
Spring Boot can auto-configure embedded H2, HSQL and Derby databases. You don’t need to provide any connection URLs, simply include a build dependency to the embedded database that you want to use.
For example, typical POM dependencies would be:
| If, for whatever reason, you do configure the connection URL for an embedded database, care should be taken to ensure that the database’s automatic shutdown is disabled. If you’re using H2 you should use |
| You need a dependency on |
29.1.2 Connection to a production database
Production database connections can also be auto-configured using a pooling DataSource. Here’s the algorithm for choosing a specific implementation:
- We prefer the Tomcat pooling
DataSourcefor its performance and concurrency, so if that is available we always choose it. - If HikariCP is available we will use it.
- If Commons DBCP is available we will use it, but we don’t recommend it in production.
- Lastly, if Commons DBCP2 is available we will use it.
If you use the spring-boot-starter-jdbc or spring-boot-starter-data-jpa ‘starter POMs’ you will automatically get a dependency to tomcat-jdbc.
| You can bypass that algorithm completely and specify the connection pool to use via the |
DataSource configuration is controlled by external configuration properties in spring.datasource.*. For example, you might declare the following section inapplication.properties:
spring.datasource.url=jdbc:mysql://localhost/test
spring.datasource.username=dbuser
spring.datasource.password=dbpass
spring.datasource.driver-class-name=com.mysql.jdbc.Driver| You often won’t need to specify the |
| For a pooling |
See DataSourceProperties for more of the supported options. These are the standard options that work regardless of the actual implementation. It is also possible to fine tune implementation-specific settings using the spring.datasource.* prefix, refer to the documentation of the connection pool implementation you are using for more details.
For instance, if you are using the Tomcat connection pool you could customize many additional settings:
# Number of ms to wait before throwing an exception if no connection is available.
spring.datasource.max-wait=10000
# Maximum number of active connections that can be allocated from this pool at the same time.
spring.datasource.max-active=50
# Validate the connection before borrowing it from the pool.
spring.datasource.test-on-borrow=true29.1.3 Connection to a JNDI DataSource
If you are deploying your Spring Boot application to an Application Server you might want to configure and manage your DataSource using your Application Servers built-in features and access it using JNDI.
The spring.datasource.jndi-name property can be used as an alternative to the spring.datasource.url, spring.datasource.username and spring.datasource.password properties to access the DataSource from a specific JNDI location. For example, the following section in application.properties shows how you can access a JBoss AS defined DataSource:
spring.datasource.jndi-name=java:jboss/datasources/customers29.2 Using JdbcTemplate
Spring’s JdbcTemplate and NamedParameterJdbcTemplate classes are auto-configured and you can @Autowire them directly into your own beans:
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.stereotype.Component;
@Component
public class MyBean {
private final JdbcTemplate jdbcTemplate;
@Autowired
public MyBean(JdbcTemplate jdbcTemplate) {
this.jdbcTemplate = jdbcTemplate;
}
// ...
}29.3 JPA and ‘Spring Data’
The Java Persistence API is a standard technology that allows you to ‘map’ objects to relational databases. The spring-boot-starter-data-jpa POM provides a quick way to get started. It provides the following key dependencies:
- Hibernate — One of the most popular JPA implementations.
- Spring Data JPA — Makes it easy to implement JPA-based repositories.
- Spring ORMs — Core ORM support from the Spring Framework.
| We won’t go into too many details of JPA or Spring Data here. You can follow the ‘Accessing Data with JPA’ guide from spring.io and read the Spring Data JPA and Hibernate reference documentation. |
29.3.1 Entity Classes
Traditionally, JPA ‘Entity’ classes are specified in a persistence.xml file. With Spring Boot this file is not necessary and instead ‘Entity Scanning’ is used. By default all packages below your main configuration class (the one annotated with @EnableAutoConfiguration or @SpringBootApplication) will be searched.
Any classes annotated with @Entity, @Embeddable or @MappedSuperclass will be considered. A typical entity class would look something like this:
package com.example.myapp.domain;
import java.io.Serializable;
import javax.persistence.*;
@Entity
public class City implements Serializable {
@Id
@GeneratedValue
private Long id;
@Column(nullable = false)
private String name;
@Column(nullable = false)
private String state;
// ... additional members, often include @OneToMany mappings
protected City() {
// no-args constructor required by JPA spec
// this one is protected since it shouldn't be used directly
}
public City(String name, String state) {
this.name = name;
this.country = country;
}
public String getName() {
return this.name;
}
public String getState() {
return this.state;
}
// ... etc
}| You can customize entity scanning locations using the |
29.3.2 Spring Data JPA Repositories
Spring Data JPA repositories are interfaces that you can define to access data. JPA queries are created automatically from your method names. For example, a CityRepository interface might declare a findAllByState(String state) method to find all cities in a given state.
For more complex queries you can annotate your method using Spring Data’s Query annotation.
Spring Data repositories usually extend from the Repository or CrudRepository interfaces. If you are using auto-configuration, repositories will be searched from the package containing your main configuration class (the one annotated with @EnableAutoConfiguration or @SpringBootApplication) down.
Here is a typical Spring Data repository:
package com.example.myapp.domain;
import org.springframework.data.domain.*;
import org.springframework.data.repository.*;
public interface CityRepository extends Repository {
Page findAll(Pageable pageable);
City findByNameAndCountryAllIgnoringCase(String name, String country);
} | We have barely scratched the surface of Spring Data JPA. For complete details check their reference documentation. |
29.3.3 Creating and dropping JPA databases
By default, JPA databases will be automatically created only if you use an embedded database (H2, HSQL or Derby). You can explicitly configure JPA settings using spring.jpa.* properties. For example, to create and drop tables you can add the following to your application.properties.
spring.jpa.hibernate.ddl-auto=create-drop| Hibernate’s own internal property name for this (if you happen to remember it better) is |
spring.jpa.properties.hibernate.globally_quoted_identifiers=truepasses hibernate.globally_quoted_identifiers to the Hibernate entity manager.
By default the DDL execution (or validation) is deferred until the ApplicationContext has started. There is also a spring.jpa.generate-ddl flag, but it is not used if Hibernate autoconfig is active because the ddl-auto settings are more fine-grained.
29.4 Using H2’s web console
The H2 database provides a browser-based console that Spring Boot can auto-configure for you. The console will be auto-configured when the following conditions are met:
- You are developing a web application
com.h2database:h2is on the classpath- You are using Spring Boot’s developer tools
| If you are not using Spring Boot’s developer tools, but would still like to make use of H2’s console, then you can do so by configuring the |
29.4.1 Changing the H2 console’s path
By default the console will be available at /h2-console. You can customize the console’s path using the spring.h2.console.path property.
29.4.2 Securing the H2 console
When Spring Security is on the classpath and basic auth is enabled, the H2 console will be automatically secured using basic auth. The following properties can be used to customize the security configuration:
security.user.rolesecurity.basic.authorize-modesecurity.basic.enabled
30. Using jOOQ
Java Object Oriented Querying (jOOQ) is a popular product from Data Geekery which generates Java code from your database, and lets you build type safe SQL queries through its fluent API. Both the commercial and open source editions can be used with Spring Boot.
30.1 Code Generation
In order to use jOOQ type-safe queries, you need to generate Java classes from your database schema. You can follow the instructions in the jOOQ user manual. If you are using the jooq-codegen-maven plugin (and you also use the spring-boot-starter-parent “parent POM”) you can safely omit the plugin’s h2.version) to declare the plugin’s database dependency. Here’s an example:
30.2 Using DSLContext
The fluent API offered by jOOQ is initiated via the org.jooq.DSLContext interface. Spring Boot will auto-configure a DSLContext as a Spring Bean and connect it to your application DataSource. To use the DSLContext you can just @Autowire it:
@Component
public class JooqExample implements CommandLineRunner {
private final DSLContext create;
@Autowired
public JooqExample(DSLContext dslContext) {
this.create = dslContext;
}
}| The jOOQ manual tends to use a variable named |
You can then use the DSLContext to construct your queries:
public List authorsBornAfter1980() {
return this.create.selectFrom(AUTHOR)
.where(AUTHOR.DATE_OF_BIRTH.greaterThan(new GregorianCalendar(1980, 0, 1)))
.fetch(AUTHOR.DATE_OF_BIRTH);
} 30.3 Customizing jOOQ
You can customize the SQL dialect used by jOOQ by setting spring.jooq.sql-dialect in your application.properties. For example, to specify Postgres you would add:
spring.jooq.sql-dialect=PostgresMore advanced customizations can be achieved by defining your own @Bean definitions which will be used when the jOOQ Configuration is created. You can define beans for the following jOOQ Types:
ConnectionProviderTransactionProviderRecordMapperProviderRecordListenerProviderExecuteListenerProviderVisitListenerProvider
You can also create your own org.jooq.Configuration @Bean if you want to take complete control of the jOOQ configuration.
31. Working with NoSQL technologies
Spring Data provides additional projects that help you access a variety of NoSQL technologies including MongoDB, Neo4J, Elasticsearch, Solr, Redis, Gemfire,Couchbase and Cassandra. Spring Boot provides auto-configuration for Redis, MongoDB, Elasticsearch, Solr and Cassandra; you can make use of the other projects, but you will need to configure them yourself. Refer to the appropriate reference documentation at projects.spring.io/spring-data.
31.1 Redis
Redis is a cache, message broker and richly-featured key-value store. Spring Boot offers basic auto-configuration for the Jedis client library and abstractions on top of it provided by Spring Data Redis. There is a spring-boot-starter-redis ‘Starter POM’ for collecting the dependencies in a convenient way.
31.1.1 Connecting to Redis
You can inject an auto-configured RedisConnectionFactory, StringRedisTemplate or vanilla RedisTemplate instance as you would any other Spring Bean. By default the instance will attempt to connect to a Redis server using localhost:6379:
@Component
public class MyBean {
private StringRedisTemplate template;
@Autowired
public MyBean(StringRedisTemplate template) {
this.template = template;
}
// ...
}If you add a @Bean of your own of any of the auto-configured types it will replace the default (except in the case of RedisTemplate the exclusion is based on the bean name ‘redisTemplate’ not its type). If commons-pool2 is on the classpath you will get a pooled connection factory by default.
31.2 MongoDB
MongoDB is an open-source NoSQL document database that uses a JSON-like schema instead of traditional table-based relational data. Spring Boot offers several conveniences for working with MongoDB, including the spring-boot-starter-data-mongodb ‘Starter POM’.
31.2.1 Connecting to a MongoDB database
You can inject an auto-configured org.springframework.data.mongodb.MongoDbFactory to access Mongo databases. By default the instance will attempt to connect to a MongoDB server using the URL mongodb://localhost/test:
import org.springframework.data.mongodb.MongoDbFactory;
import com.mongodb.DB;
@Component
public class MyBean {
private final MongoDbFactory mongo;
@Autowired
public MyBean(MongoDbFactory mongo) {
this.mongo = mongo;
}
// ...
public void example() {
DB db = mongo.getDb();
// ...
}
}You can set spring.data.mongodb.uri property to change the URL and configure additional settings such as the replica set:
spring.data.mongodb.uri=mongodb://user:[email protected]:12345,mongo2.example.com:23456/testAlternatively, as long as you’re using Mongo 2.x, specify a host/port. For example, you might declare the following in your application.properties:
spring.data.mongodb.host=mongoserver
spring.data.mongodb.port=27017|
|
| If |
| If you aren’t using Spring Data Mongo you can inject |
You can also declare your own MongoDbFactory or Mongo bean if you want to take complete control of establishing the MongoDB connection.
31.2.2 MongoTemplate
Spring Data Mongo provides a MongoTemplate class that is very similar in its design to Spring’s JdbcTemplate. As with JdbcTemplate Spring Boot auto-configures a bean for you to simply inject:
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.mongodb.core.MongoTemplate;
import org.springframework.stereotype.Component;
@Component
public class MyBean {
private final MongoTemplate mongoTemplate;
@Autowired
public MyBean(MongoTemplate mongoTemplate) {
this.mongoTemplate = mongoTemplate;
}
// ...
}See the MongoOperations Javadoc for complete details.
31.2.3 Spring Data MongoDB repositories
Spring Data includes repository support for MongoDB. As with the JPA repositories discussed earlier, the basic principle is that queries are constructed for you automatically based on method names.
In fact, both Spring Data JPA and Spring Data MongoDB share the same common infrastructure; so you could take the JPA example from earlier and, assuming that City is now a Mongo data class rather than a JPA @Entity, it will work in the same way.
package com.example.myapp.domain;
import org.springframework.data.domain.*;
import org.springframework.data.repository.*;
public interface CityRepository extends Repository {
Page findAll(Pageable pageable);
City findByNameAndCountryAllIgnoringCase(String name, String country);
} | For complete details of Spring Data MongoDB, including its rich object mapping technologies, refer to their reference documentation. |
31.2.4 Embedded Mongo
Spring Boot offers auto-configuration for Embedded Mongo. To use it in your Spring Boot application add a dependency onde.flapdoodle.embed:de.flapdoodle.embed.mongo.
The port that Mongo will listen on can be configured using the spring.data.mongodb.port property. To use a randomly allocated free port use a value of zero. The MongoClient created by MongoAutoConfiguration will be automatically configured to use the randomly allocated port.
If you have SLF4J on the classpath, output produced by Mongo will be automatically routed to a logger named org.springframework.boot.autoconfigure.mongo.embedded.EmbeddedMongo.
You can declare your own IMongodConfig and IRuntimeConfig beans to take control of the Mongo instance’s configuration and logging routing.
31.3 Gemfire
Spring Data Gemfire provides convenient Spring-friendly tools for accessing the Pivotal Gemfire data management platform. There is a spring-boot-starter-data-gemfire ‘Starter POM’ for collecting the dependencies in a convenient way. There is currently no auto-configuration support for Gemfire, but you can enable Spring Data Repositories with a single annotation (@EnableGemfireRepositories).
31.4 Solr
Apache Solr is a search engine. Spring Boot offers basic auto-configuration for the Solr 4 client library and abstractions on top of it provided by Spring Data Solr. There is a spring-boot-starter-data-solr ‘Starter POM’ for collecting the dependencies in a convenient way.
| Solr 5 is currently not supported and the auto-configuration will not be enabled by a Solr 5 dependency. |
31.4.1 Connecting to Solr
You can inject an auto-configured SolrServer instance as you would any other Spring bean. By default the instance will attempt to connect to a server usinglocalhost:8983/solr:
@Component
public class MyBean {
private SolrServer solr;
@Autowired
public MyBean(SolrServer solr) {
this.solr = solr;
}
// ...
}If you add a @Bean of your own of type SolrServer it will replace the default.
31.4.2 Spring Data Solr repositories
Spring Data includes repository support for Apache Solr. As with the JPA repositories discussed earlier, the basic principle is that queries are constructed for you automatically based on method names.
In fact, both Spring Data JPA and Spring Data Solr share the same common infrastructure; so you could take the JPA example from earlier and, assuming that City is now a @SolrDocument class rather than a JPA @Entity, it will work in the same way.
| For complete details of Spring Data Solr, refer to their reference documentation. |
31.5 Elasticsearch
Elasticsearch is an open source, distributed, real-time search and analytics engine. Spring Boot offers basic auto-configuration for the Elasticsearch and abstractions on top of it provided by Spring Data Elasticsearch. There is a spring-boot-starter-data-elasticsearch ‘Starter POM’ for collecting the dependencies in a convenient way.
31.5.1 Connecting to Elasticsearch
You can inject an auto-configured ElasticsearchTemplate or Elasticsearch Client instance as you would any other Spring Bean. By default the instance will attempt to connect to a local in-memory server (a NodeClient in Elasticsearch terms), but you can switch to a remote server (i.e. a TransportClient) by setting spring.data.elasticsearch.cluster-nodes to a comma-separated ‘host:port’ list.
@Component
public class MyBean {
private ElasticsearchTemplate template;
@Autowired
public MyBean(ElasticsearchTemplate template) {
this.template = template;
}
// ...
}If you add a @Bean of your own of type ElasticsearchTemplate it will replace the default.
31.5.2 Spring Data Elasticsearch repositories
Spring Data includes repository support for Elasticsearch. As with the JPA repositories discussed earlier, the basic principle is that queries are constructed for you automatically based on method names.
In fact, both Spring Data JPA and Spring Data Elasticsearch share the same common infrastructure; so you could take the JPA example from earlier and, assuming that City is now an Elasticsearch @Document class rather than a JPA @Entity, it will work in the same way.
| For complete details of Spring Data Elasticsearch, refer to their reference documentation. |
31.6 Cassandra
Cassandra is an open source, distributed database management system designed to handle large amounts of data across many commodity servers. Spring Boot offers auto-configuration for Cassandra and abstractions on top of it provided by Spring Data Cassandra. There is a spring-boot-starter-data-cassandra ‘Starter POM’ for collecting the dependencies in a convenient way.
31.6.1 Connecting to Cassandra
You can inject an auto-configured CassandraTemplate or a Cassandra Session instance as you would any other Spring Bean. The spring.data.cassandra.* properties can be used to customize the connection. Generally you will to provide keyspace-name and contact-pointsproperties:
spring.data.cassandra.keyspace-name=mykeyspace
spring.data.cassandra.contact-points=cassandrahost1,cassandrahost2@Component
public class MyBean {
private CassandraTemplate template;
@Autowired
public MyBean(CassandraTemplate template) {
this.template = template;
}
// ...
}If you add a @Bean of your own of type CassandraTemplate it will replace the default.
31.6.2 Spring Data Cassandra repositories
Spring Data includes basic repository support for Cassandra. Currently this is more limited than the JPA repositories discussed earlier, and will need to annotate finder methods with @Query.
| For complete details of Spring Data Cassandra, refer to their reference documentation. |
32. Caching
The Spring Framework provides support for transparently adding caching to an application. At its core, the abstraction applies caching to methods, reducing thus the number of executions based on the information available in the cache. The caching logic is applied transparently, without any interference to the invoker.
| Check the relevant section of the Spring Framework reference for more details. |
In a nutshell, adding caching to an operation of your service is as easy as adding the relevant annotation to its method:
import javax.cache.annotation.CacheResult;
import org.springframework.stereotype.Component;
@Component
public class MathService {
@CacheResult
public int computePiDecimal(int i) {
// ...
}
}| You can either use the standard JSR-107 (JCache) annotations or Spring’s own caching annotations transparently. We strongly advise you however to not mix and match them. |
| It is also possible to update or evict data from the cache transparently. |
32.1 Supported cache providers
The cache abstraction does not provide an actual store and relies on abstraction materialized by the org.springframework.cache.Cache andorg.springframework.cache.CacheManager interfaces. Spring Boot auto-configures a suitable CacheManager according to the implementation as long as the caching support is enabled via the @EnableCaching annotation.
| Use the |
Spring Boot tries to detect the following providers (in this order):
- Generic
- JCache (JSR-107)
- EhCache 2.x
- Hazelcast
- Infinispan
- Redis
- Guava
- Simple
It is also possible to force the cache provider to use via the spring.cache.type property.
If the CacheManager is auto-configured by Spring Boot, you can further tune its configuration before it is fully initialized by exposing a bean implementing theCacheManagerCustomizer interface. The following set the cache names to use.
@Bean
public CacheManagerCustomizer cacheManagerCustomizer() {
return new CacheManagerCustomizer() {
@Override
public void customize(ConcurrentMapCacheManager cacheManager) {
cacheManager.setCacheNames(Arrays.asList("one", "two"));
}
};
} | === In the example above, a |
32.1.1 Generic
Generic caching is used if the context defines at least one org.springframework.cache.Cache bean, a CacheManager wrapping them is configured.
32.1.2 JCache
JCache is bootstrapped via the presence of a javax.cache.spi.CachingProvider on the classpath (i.e. a JSR-107 compliant caching library). It might happen than more that one provider is present, in which case the provider must be explicitly specified. Even if the JSR-107 standard does not enforce a standardized way to define the location of the configuration file, Spring Boot does its best to accommodate with implementation details.
# Only necessary if more than one provider is present
spring.cache.jcache.provider=com.acme.MyCachingProvider
spring.cache.jcache.config=classpath:acme.xml| Since a cache library may offer both a native implementation and JSR-107 support Spring Boot will prefer the JSR-107 support so that the same features are available if you switch to a different JSR-107 implementation. |
There are several ways to customize the underlying javax.cache.cacheManager:
- Caches can be created on startup via the
spring.cache.cache-namesproperty. If a customjavax.cache.configuration.Configurationbean is defined, it is used to customize them. org.springframework.boot.autoconfigure.cache.JCacheManagerCustomizerbeans are invoked with the reference of theCacheManagerfor full customization.
| If a standard |
32.1.3 EhCache 2.x
EhCache 2.x is used if a file named ehcache.xml can be found at the root of the classpath. If EhCache 2.x and such file is present it is used to bootstrap the cache manager. An alternate configuration file can be provide a well using:
spring.cache.ehcache.config=classpath:config/another-config.xml32.1.4 Hazelcast
Spring Boot has a general support for Hazelcast. If a HazelcastInstance has been auto-configured, it is automatically wrapped in a CacheManager.
If for some reason you need a different HazelcastInstance for caching, you can request Spring Boot to create a separate one that will be only used by theCacheManager:
spring.cache.hazelcast.config=classpath:config/my-cache-hazelcast.xml| If a separate |
32.1.5 Infinispan
Infinispan has no default configuration file location so it must be specified explicitly (or the default bootstrap is used).
spring.cache.infinispan.config=infinispan.xmlCaches can be created on startup via the spring.cache.cache-names property. If a custom ConfigurationBuilder bean is defined, it is used to customize them.
32.1.6 Redis
If Redis is available and configured, the RedisCacheManager is auto-configured. It is also possible to create additional caches on startup using the spring.cache.cache-names property.
32.1.7 Guava
If Guava is present, a GuavaCacheManager is auto-configured. Caches can be created on startup using the spring.cache.cache-names property and customized by one of the following (in this order):
- A cache spec defined by
spring.cache.guava.spec - A
com.google.common.cache.CacheBuilderSpecbean is defined - A
com.google.common.cache.CacheBuilderbean is defined
For instance, the following configuration creates a foo and bar caches with a maximum size of 500 and a time to live of 10 minutes
spring.cache.cache-names=foo,bar
spring.cache.guava.spec=maximumSize=500,expireAfterAccess=600sBesides, if a com.google.common.cache.CacheLoader bean is defined, it is automatically associated to the GuavaCacheManager.
32.1.8 Simple
If none of these options worked out, a simple implementation using ConcurrentHashMap as cache store is configured. This is the default if no caching library is present in your application.
33. Messaging
The Spring Framework provides extensive support for integrating with messaging systems: from simplified use of the JMS API using JmsTemplate to a complete infrastructure to receive messages asynchronously. Spring AMQP provides a similar feature set for the ‘Advanced Message Queuing Protocol’ and Spring Boot also provides auto-configuration options for RabbitTemplate and RabbitMQ. There is also support for STOMP messaging natively in Spring WebSocket and Spring Boot has support for that through starters and a small amount of auto-configuration.
33.1 JMS
The javax.jms.ConnectionFactory interface provides a standard method of creating a javax.jms.Connection for interacting with a JMS broker. Although Spring needs a ConnectionFactory to work with JMS, you generally won’t need to use it directly yourself and you can instead rely on higher level messaging abstractions (see the relevant section of the Spring Framework reference documentation for details). Spring Boot also auto-configures the necessary infrastructure to send and receive messages.
33.1.1 ActiveMQ support
Spring Boot can also configure a ConnectionFactory when it detects that ActiveMQ is available on the classpath. If the broker is present, an embedded broker is started and configured automatically (as long as no broker URL is specified through configuration).
ActiveMQ configuration is controlled by external configuration properties in spring.activemq.*. For example, you might declare the following section inapplication.properties:
spring.activemq.broker-url=tcp://192.168.1.210:9876
spring.activemq.user=admin
spring.activemq.password=secretSee ActiveMQProperties for more of the supported options.
By default, ActiveMQ creates a destination if it does not exist yet, so destinations are resolved against their provided names.
33.1.2 Artemis support
Apache Artemis was formed in 2015 when HornetQ was donated to the Apache Foundation. All the features listed in the Section 33.1.3, “HornetQ support”section below can be applied to Artemis. Simply replace spring.hornetq.* properties with spring.artemis.* and use spring-boot-starter-artemisinstead of spring-boot-starter-hornetq. If you want to embed Artemis, make sure to add org.apache.activemq:artemis-jms-server to the dependencies of your application.
| You should not try and use Artemis and HornetQ and the same time. |
33.1.3 HornetQ support
Spring Boot can auto-configure a ConnectionFactory when it detects that HornetQ is available on the classpath. If the broker is present, an embedded broker is started and configured automatically (unless the mode property has been explicitly set). The supported modes are: embedded (to make explicit that an embedded broker is required and should lead to an error if the broker is not available in the classpath), and native to connect to a broker using the nettytransport protocol. When the latter is configured, Spring Boot configures a ConnectionFactory connecting to a broker running on the local machine with the default settings.
| If you are using |
HornetQ configuration is controlled by external configuration properties in spring.hornetq.*. For example, you might declare the following section inapplication.properties:
spring.hornetq.mode=native
spring.hornetq.host=192.168.1.210
spring.hornetq.port=9876When embedding the broker, you can choose if you want to enable persistence, and the list of destinations that should be made available. These can be specified as a comma-separated list to create them with the default options; or you can define bean(s) of typeorg.hornetq.jms.server.config.JMSQueueConfiguration or org.hornetq.jms.server.config.TopicConfiguration, for advanced queue and topic configurations respectively.
See HornetQProperties for more of the supported options.
No JNDI lookup is involved at all and destinations are resolved against their names, either using the ‘name’ attribute in the HornetQ configuration or the names provided through configuration.
33.1.4 Using a JNDI ConnectionFactory
If you are running your application in an Application Server Spring Boot will attempt to locate a JMS ConnectionFactory using JNDI. By default the locations java:/JmsXA and java:/XAConnectionFactory will be checked. You can use the spring.jms.jndi-name property if you need to specify an alternative location:
spring.jms.jndi-name=java:/MyConnectionFactory33.1.5 Sending a message
Spring’s JmsTemplate is auto-configured and you can autowire it directly into your own beans:
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jms.core.JmsTemplate;
import org.springframework.stereotype.Component;
@Component
public class MyBean {
private final JmsTemplate jmsTemplate;
@Autowired
public MyBean(JmsTemplate jmsTemplate) {
this.jmsTemplate = jmsTemplate;
}
// ...
}|
|
33.1.6 Receiving a message
When the JMS infrastructure is present, any bean can be annotated with @JmsListener to create a listener endpoint. If no JmsListenerContainerFactoryhas been defined, a default one is configured automatically.
The default factory is transactional by default. If you are running in an infrastructure where a JtaTransactionManager is present, it will be associated to the listener container by default. If not, the sessionTransacted flag will be enabled. In that latter scenario, you can associate your local data store transaction to the processing of an incoming message by adding @Transactional on your listener method (or a delegate thereof). This will make sure that the incoming message is acknowledged once the local transaction has completed. This also includes sending response messages that have been performed on the same JMS session.
The following component creates a listener endpoint on the someQueue destination:
@Component
public class MyBean {
@JmsListener(destination = "someQueue")
public void processMessage(String content) {
// ...
}
}| Check the Javadoc of |
If you need to create more JmsListenerContainerFactory instances or if you want to override the default, Spring Boot provides a DefaultJmsListenerContainerFactoryConfigurer that you can use to initialize a DefaultJmsListenerContainerFactory with the same settings as the one that is auto-configured.
For instance, the following exposes another factory that uses a specific MessageConverter:
@Configuration
static class JmsConfiguration {
@Bean
public DefaultJmsListenerContainerFactory myFactory(
DefaultJmsListenerContainerFactoryConfigurer configurer) {
DefaultJmsListenerContainerFactory factory =
new DefaultJmsListenerContainerFactory();
configurer.configure(factory, connectionFactory());
factory.setMessageConverter(myMessageConverter());
return factory;
}
}That you can use in any @JmsListener-annotated method as follows:
@Component
public class MyBean {
@JmsListener(destination = "someQueue", containerFactory="myFactory")
public void processMessage(String content) {
// ...
}
}33.2 AMQP
The Advanced Message Queuing Protocol (AMQP) is a platform-neutral, wire-level protocol for message-oriented middleware. The Spring AMQP project applies core Spring concepts to the development of AMQP-based messaging solutions.
33.2.1 RabbitMQ support
RabbitMQ is a lightweight, reliable, scalable and portable message broker based on the AMQP protocol. Spring uses RabbitMQ to communicate using the AMQP protocol.
RabbitMQ configuration is controlled by external configuration properties in spring.rabbitmq.*. For example, you might declare the following section inapplication.properties:
spring.rabbitmq.host=localhost
spring.rabbitmq.port=5672
spring.rabbitmq.username=admin
spring.rabbitmq.password=secretSee RabbitProperties for more of the supported options.
| Check Understanding AMQP, the protocol used by RabbitMQ for more details. |
33.2.2 Sending a message
Spring’s AmqpTemplate and AmqpAdmin are auto-configured and you can autowire them directly into your own beans:
import org.springframework.amqp.core.AmqpAdmin;
import org.springframework.amqp.core.AmqpTemplate;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
@Component
public class MyBean {
private final AmqpAdmin amqpAdmin;
private final AmqpTemplate amqpTemplate;
@Autowired
public MyBean(AmqpAdmin amqpAdmin, AmqpTemplate amqpTemplate) {
this.amqpAdmin = amqpAdmin;
this.amqpTemplate = amqpTemplate;
}
// ...
}|
|
Any org.springframework.amqp.core.Queue that is defined as a bean will be automatically used to declare a corresponding queue on the RabbitMQ instance if necessary.
33.2.3 Receiving a message
When the Rabbit infrastructure is present, any bean can be annotated with @RabbitListener to create a listener endpoint. If no RabbitListenerContainerFactory has been defined, a default one is configured automatically.
The following component creates a listener endpoint on the someQueue queue:
@Component
public class MyBean {
@RabbitListener(queues = "someQueue")
public void processMessage(String content) {
// ...
}
}| Check the Javadoc of |
If you need to create more RabbitListenerContainerFactory instances or if you want to override the default, Spring Boot provides a SimpleRabbitListenerContainerFactoryConfigurer that you can use to initialize a SimpleRabbitListenerContainerFactory with the same settings as the one that is auto-configured.
For instance, the following exposes another factory that uses a specific MessageConverter:
@Configuration
static class RabbitConfiguration {
@Bean
public SimpleRabbitListenerContainerFactory myFactory(
SimpleRabbitListenerContainerFactoryConfigurer configurer) {
SimpleRabbitListenerContainerFactory factory =
new SimpleRabbitListenerContainerFactory();
configurer.configure(factory, connectionFactory);
factory.setMessageConverter(myMessageConverter());
return factory;
}
}That you can use in any @RabbitListener-annotated method as follows:
@Component
public class MyBean {
@RabbitListener(queues = "someQueue", containerFactory="myFactory")
public void processMessage(String content) {
// ...
}
}34. Sending email
The Spring Framework provides an easy abstraction for sending email using the JavaMailSender interface and Spring Boot provides auto-configuration for it as well as a starter module.
| Check the reference documentation for a detailed explanation of how you can use |
If spring.mail.host and the relevant libraries (as defined by spring-boot-starter-mail) are available, a default JavaMailSender is created if none exists. The sender can be further customized by configuration items from the spring.mail namespace, see the MailProperties for more details.
35. Distributed Transactions with JTA
Spring Boot supports distributed JTA transactions across multiple XA resources using either an Atomikos or Bitronix embedded transaction manager. JTA transactions are also supported when deploying to a suitable Java EE Application Server.
When a JTA environment is detected, Spring’s JtaTransactionManager will be used to manage transactions. Auto-configured JMS, DataSource and JPA beans will be upgraded to support XA transactions. You can use standard Spring idioms such as @Transactional to participate in a distributed transaction. If you are within a JTA environment and still want to use local transactions you can set the spring.jta.enabled property to false to disable the JTA auto-configuration.
35.1 Using an Atomikos transaction manager
Atomikos is a popular open source transaction manager which can be embedded into your Spring Boot application. You can use the spring-boot-starter-jta-atomikos Starter POM to pull in the appropriate Atomikos libraries. Spring Boot will auto-configure Atomikos and ensure that appropriate depends-on settings are applied to your Spring beans for correct startup and shutdown ordering.
By default Atomikos transaction logs will be written to a transaction-logs directory in your application home directory (the directory in which your application jar file resides). You can customize this directory by setting a spring.jta.log-dir property in your application.properties file. Properties starting spring.jta. can also be used to customize the Atomikos UserTransactionServiceImp. See the AtomikosProperties Javadoc for complete details.
| To ensure that multiple transaction managers can safely coordinate the same resource managers, each Atomikos instance must be configured with a unique ID. By default this ID is the IP address of the machine on which Atomikos is running. To ensure uniqueness in production, you should configure the |
35.2 Using a Bitronix transaction manager
Bitronix is another popular open source JTA transaction manager implementation. You can use the spring-boot-starter-jta-bitronix starter POM to add the appropriate Bitronix dependencies to your project. As with Atomikos, Spring Boot will automatically configure Bitronix and post-process your beans to ensure that startup and shutdown ordering is correct.
By default Bitronix transaction log files (part1.btm and part2.btm) will be written to a transaction-logs directory in your application home directory. You can customize this directory by using the spring.jta.log-dir property. Properties starting spring.jta. are also bound to the bitronix.tm.Configuration bean, allowing for complete customization. See the Bitronix documentation for details.
| To ensure that multiple transaction managers can safely coordinate the same resource managers, each Bitronix instance must be configured with a unique ID. By default this ID is the IP address of the machine on which Bitronix is running. To ensure uniqueness in production, you should configure the |
35.3 Using a Java EE managed transaction manager
If you are packaging your Spring Boot application as a war or ear file and deploying it to a Java EE application server, you can use your application servers built-in transaction manager. Spring Boot will attempt to auto-configure a transaction manager by looking at common JNDI locations (java:comp/UserTransaction, java:comp/TransactionManager etc). If you are using a transaction service provided by your application server, you will generally also want to ensure that all resources are managed by the server and exposed over JNDI. Spring Boot will attempt to auto-configure JMS by looking for a ConnectionFactory at the JNDI path java:/JmsXA or java:/XAConnectionFactory and you can use the spring.datasource.jndi-nameproperty to configure your DataSource.
35.4 Mixing XA and non-XA JMS connections
When using JTA, the primary JMS ConnectionFactory bean will be XA aware and participate in distributed transactions. In some situations you might want to process certain JMS messages using a non-XA ConnectionFactory. For example, your JMS processing logic might take longer than the XA timeout.
If you want to use a non-XA ConnectionFactory you can inject the nonXaJmsConnectionFactory bean rather than the @PrimaryjmsConnectionFactory bean. For consistency the jmsConnectionFactory bean is also provided using the bean alias xaJmsConnectionFactory.
For example:
// Inject the primary (XA aware) ConnectionFactory
@Autowired
private ConnectionFactory defaultConnectionFactory;
// Inject the XA aware ConnectionFactory (uses the alias and injects the same as above)
@Autowired
@Qualifier("xaJmsConnectionFactory")
private ConnectionFactory xaConnectionFactory;
// Inject the non-XA aware ConnectionFactory
@Autowired
@Qualifier("nonXaJmsConnectionFactory")
private ConnectionFactory nonXaConnectionFactory;35.5 Supporting an alternative embedded transaction manager
The XAConnectionFactoryWrapper and XADataSourceWrapper interfaces can be used to support alternative embedded transaction managers. The interfaces are responsible for wrapping XAConnectionFactory and XADataSource beans and exposing them as regular ConnectionFactory and DataSource beans which will transparently enroll in the distributed transaction. DataSource and JMS auto-configuration will use JTA variants as long as you have a JtaTransactionManager bean and appropriate XA wrapper beans registered within your ApplicationContext.
The BitronixXAConnectionFactoryWrapper and BitronixXADataSourceWrapper provide good examples of how to write XA wrappers.
36. Hazelcast
If hazelcast is on the classpath, Spring Boot will auto-configure an HazelcastInstance that you can inject in your application. The HazelcastInstance is only created if a configuration is found.
You can define a com.hazelcast.config.Config bean and we’ll use that. If your configuration defines an instance name, we’ll try to locate an existing instance rather than creating a new one.
You could also specify the hazelcast.xml configuration file to use via configuration:
spring.hazelcast.config=classpath:config/my-hazelcast.xmlOtherwise, Spring Boot tries to find the Hazelcast configuration from the default locations, that is hazelcast.xml in the working directory or at the root of the classpath. We also check if the hazelcast.config system property is set. Check the Hazelcast documentation for more details.
| Spring Boot also has an explicit caching support for Hazelcast. The |
37. Spring Integration
Spring Integration provides abstractions over messaging and also other transports such as HTTP, TCP etc. If Spring Integration is available on your classpath it will be initialized through the @EnableIntegration annotation. Message processing statistics will be published over JMX if 'spring-integration-jmx' is also on the classpath. See the IntegrationAutoConfiguration class for more details.
38. Spring Session
Spring Session provides support for managing a user’s session information. If you are writing a web application and Spring Session and Spring Data Redis are both on the classpath, Spring Boot will auto-configure Spring Session through its @EnableRedisHttpSession. Session data will be stored in Redis and the session timeout can be configured using the server.session.timeout property.
39. Monitoring and management over JMX
Java Management Extensions (JMX) provide a standard mechanism to monitor and manage applications. By default Spring Boot will create an MBeanServerwith bean id ‘mbeanServer’ and expose any of your beans that are annotated with Spring JMX annotations (@ManagedResource, @ManagedAttribute, @ManagedOperation).
See the JmxAutoConfiguration class for more details.
40. Testing
Spring Boot provides a number of useful tools for testing your application. The spring-boot-starter-test POM provides Spring Test, JUnit, Hamcrest and Mockito dependencies. There are also useful test utilities in the core spring-boot module under the org.springframework.boot.test package.
40.1 Test scope dependencies
If you use the spring-boot-starter-test ‘Starter POM’ (in the test scope), you will find the following provided libraries:
- Spring Test — integration test support for Spring applications.
- JUnit — The de-facto standard for unit testing Java applications.
- Hamcrest — A library of matcher objects (also known as constraints or predicates) allowing
assertThatstyle JUnit assertions. - Mockito — A Java mocking framework.
These are common libraries that we generally find useful when writing tests. You are free to add additional test dependencies of your own if these don’t suit your needs.
40.2 Testing Spring applications
One of the major advantages of dependency injection is that it should make your code easier to unit test. You can simply instantiate objects using the newoperator without even involving Spring. You can also use mock objects instead of real dependencies.
Often you need to move beyond ‘unit testing’ and start ‘integration testing’ (with a Spring ApplicationContext actually involved in the process). It’s useful to be able to perform integration testing without requiring deployment of your application or needing to connect to other infrastructure.
The Spring Framework includes a dedicated test module for just such integration testing. You can declare a dependency directly to org.springframework:spring-test or use the spring-boot-starter-test ‘Starter POM’ to pull it in transitively.
If you have not used the spring-test module before you should start by reading the relevant section of the Spring Framework reference documentation.
40.3 Testing Spring Boot applications
A Spring Boot application is just a Spring ApplicationContext so nothing very special has to be done to test it beyond what you would normally do with a vanilla Spring context. One thing to watch out for though is that the external properties, logging and other features of Spring Boot are only installed in the context by default if you use SpringApplication to create it.
Spring Boot provides a @SpringApplicationConfiguration annotation as an alternative to the standard spring-test @ContextConfigurationannotation. If you use @SpringApplicationConfiguration to configure the ApplicationContext used in your tests, it will be created via SpringApplication and you will get the additional Spring Boot features.
For example:
@RunWith(SpringJUnit4ClassRunner.class)
@SpringApplicationConfiguration(SampleDataJpaApplication.class)
public class CityRepositoryIntegrationTests {
@Autowired
CityRepository repository;
// ...
}| The context loader guesses whether you want to test a web application or not (e.g. with |
If you want a web application to start up and listen on its normal port, so you can test it with HTTP (e.g. using RestTemplate), annotate your test class (or one of its superclasses) with @WebIntegrationTest. This can be very useful because it means you can test the full stack of your application, but also inject its components into the test class and use them to assert the internal state of the application after an HTTP interaction. For example:
@RunWith(SpringJUnit4ClassRunner.class)
@SpringApplicationConfiguration(SampleDataJpaApplication.class)
@WebIntegrationTest
public class CityRepositoryIntegrationTests {
@Autowired
CityRepository repository;
RestTemplate restTemplate = new TestRestTemplate();
// ... interact with the running server
}| Spring’s test framework will cache application contexts between tests. Therefore, as long as your tests share the same configuration, the time consuming process of starting and stopping the server will only happen once, regardless of the number of tests that actually run. |
To change the port you can add environment properties to @WebIntegrationTest as colon- or equals-separated name-value pairs, e.g. @WebIntegrationTest("server.port:9000"). Additionally you can set the server.port and management.port properties to 0 in order to run your integration tests using random ports. For example:
@RunWith(SpringJUnit4ClassRunner.class)
@SpringApplicationConfiguration(MyApplication.class)
@WebIntegrationTest({"server.port=0", "management.port=0"})
public class SomeIntegrationTests {
// ...
}Alternatively, you can use the randomPort convenience attribute to set server.port=0. For example:
@RunWith(SpringJUnit4ClassRunner.class)
@SpringApplicationConfiguration(MyApplication.class)
@WebIntegrationTest(randomPort = true)
public class SomeIntegrationTests {
// ...
}See Section 70.4, “Discover the HTTP port at runtime” for a description of how you can discover the actual port that was allocated for the duration of the tests.
40.3.1 Using Spock to test Spring Boot applications
If you wish to use Spock to test a Spring Boot application you should add a dependency on Spock’s spock-spring module to your application’s build. spock-spring integrates Spring’s test framework into Spock.
| The annotations described above can be used with Spock, i.e. you can annotate your |
40.4 Test utilities
A few test utility classes are packaged as part of spring-boot that are generally useful when testing your application.
40.4.1 ConfigFileApplicationContextInitializer
ConfigFileApplicationContextInitializer is an ApplicationContextInitializer that can apply to your tests to load Spring Boot application.properties files. You can use this when you don’t need the full features provided by @SpringApplicationConfiguration.
@ContextConfiguration(classes = Config.class,
initializers = ConfigFileApplicationContextInitializer.class)40.4.2 EnvironmentTestUtils
EnvironmentTestUtils allows you to quickly add properties to a ConfigurableEnvironment or ConfigurableApplicationContext. Simply call it withkey=value strings:
EnvironmentTestUtils.addEnvironment(env, "org=Spring", "name=Boot");40.4.3 OutputCapture
OutputCapture is a JUnit Rule that you can use to capture System.out and System.err output. Simply declare the capture as a @Rule then use toString() for assertions:
import org.junit.Rule;
import org.junit.Test;
import org.springframework.boot.test.OutputCapture;
import static org.hamcrest.Matchers.*;
import static org.junit.Assert.*;
public class MyTest {
@Rule
public OutputCapture capture = new OutputCapture();
@Test
public void testName() throws Exception {
System.out.println("Hello World!");
assertThat(capture.toString(), containsString("World"));
}
}40.4.4 TestRestTemplate
TestRestTemplate is a convenience subclass of Spring’s RestTemplate that is useful in integration tests. You can get a vanilla template or one that sends Basic HTTP authentication (with a username and password). In either case the template will behave in a test-friendly way: not following redirects (so you can assert the response location), ignoring cookies (so the template is stateless), and not throwing exceptions on server-side errors. It is recommended, but not mandatory, to use Apache HTTP Client (version 4.3.2 or better), and if you have that on your classpath the TestRestTemplate will respond by configuring the client appropriately.
public class MyTest {
RestTemplate template = new TestRestTemplate();
@Test
public void testRequest() throws Exception {
HttpHeaders headers = template.getForEntity("http://myhost.com", String.class).getHeaders();
assertThat(headers.getLocation().toString(), containsString("myotherhost"));
}
}41. Creating your own auto-configuration
If you work in a company that develops shared libraries, or if you work on an open-source or commercial library, you might want to develop your own auto-configuration. Auto-configuration classes can be bundled in external jars and still be picked-up by Spring Boot.
Auto-configuration can be associated to a "starter" that provides the auto-configuration code as well as the typical libraries that you would use with it. We will first cover what you need to know to build your own auto-configuration and we will move on to the typical steps required to create a custom starter.
| A demo project is available to showcase how you can create a starter step by step. |
41.1 Understanding auto-configured beans
Under the hood, auto-configuration is implemented with standard @Configuration classes. Additional @Conditional annotations are used to constrain when the auto-configuration should apply. Usually auto-configuration classes use @ConditionalOnClass and @ConditionalOnMissingBean annotations. This ensures that auto-configuration only applies when relevant classes are found and when you have not declared your own @Configuration.
You can browse the source code of spring-boot-autoconfigure to see the @Configuration classes that we provide (see theMETA-INF/spring.factories file).
41.2 Locating auto-configuration candidates
Spring Boot checks for the presence of a META-INF/spring.factories file within your published jar. The file should list your configuration classes under theEnableAutoConfiguration key.
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
com.mycorp.libx.autoconfigure.LibXAutoConfiguration,\
com.mycorp.libx.autoconfigure.LibXWebAutoConfigurationYou can use the @AutoConfigureAfter or @AutoConfigureBefore annotations if your configuration needs to be applied in a specific order. For example, if you provide web-specific configuration, your class may need to be applied after WebMvcAutoConfiguration.
If you want to order certain auto-configurations that shouldn’t have any direct knowledge of each other, you can also use @AutoconfigureOrder. That annotation has the same semantic as the regular @Order annotation but provides a dedicated order for auto-configuration classes.
41.3 Condition annotations
You almost always want to include one or more @Conditional annotations on your auto-configuration class. The @ConditionalOnMissingBean is one common example that is used to allow developers to ‘override’ auto-configuration if they are not happy with your defaults.
Spring Boot includes a number of @Conditional annotations that you can reuse in your own code by annotating @Configuration classes or individual @Bean methods.
41.3.1 Class conditions
The @ConditionalOnClass and @ConditionalOnMissingClass annotations allows configuration to be included based on the presence or absence of specific classes. Due to the fact that annotation metadata is parsed using ASM you can actually use the value attribute to refer to the real class, even though that class might not actually appear on the running application classpath. You can also use the name attribute if you prefer to specify the class name using a String value.
41.3.2 Bean conditions
The @ConditionalOnBean and @ConditionalOnMissingBean annotations allow a bean to be included based on the presence or absence of specific beans. You can use the value attribute to specify beans by type, or name to specify beans by name. The search attribute allows you to limit the ApplicationContext hierarchy that should be considered when searching for beans.
| You need to be very careful about the order that bean definitions are added as these conditions are evaluated based on what has been processed so far. For this reason, we recommend only using |
|
|
41.3.3 Property conditions
The @ConditionalOnProperty annotation allows configuration to be included based on a Spring Environment property. Use the prefix and name attributes to specify the property that should be checked. By default any property that exists and is not equal to false will be matched. You can also create more advanced checks using the havingValue and matchIfMissing attributes.
41.3.4 Resource conditions
The @ConditionalOnResource annotation allows configuration to be included only when a specific resource is present. Resources can be specified using the usual Spring conventions, for example, file:/home/user/test.dat.
41.3.5 Web application conditions
The @ConditionalOnWebApplication and @ConditionalOnNotWebApplication annotations allow configuration to be included depending on whether the application is a 'web application'. A web application is any application that is using a Spring WebApplicationContext, defines a session scope or has a StandardServletEnvironment.
41.3.6 SpEL expression conditions
The @ConditionalOnExpression annotation allows configuration to be included based on the result of a SpEL expression.
41.4 Creating your own starter
A full Spring Boot starter for a library may contain the following components:
- The
autoconfiguremodule that contains the auto-configuration code. - The
startermodule that provides a dependency to the autoconfigure module as well as the library and any additional dependencies that are typically useful. In a nutshell, adding the starter should be enough to start using that library.
| You may combine the auto-configuration code and the dependency management in a single module if you don’t need to separate those two concerns. |
41.4.1 Naming
Please make sure to provide a proper namespace for your starter. Do not start your module names with spring-boot, even if you are using a different Maven groupId. We may offer an official support for the thing you’re auto-configuring in the future.
Here is a rule of thumb. Let’s assume that you are creating a starter for "acme", name the auto-configure module acme-spring-boot-autoconfigure and the starter acme-spring-boot-starter. If you only have one module combining the two, use acme-spring-boot-starter.
Besides, if your starter provides configuration keys, use a proper namespace for them. In particular, do not include your keys in the namespaces that Spring Boot uses (e.g. server, management, spring, etc). These are "ours" and we may improve/modify them in the future in such a way it could break your things.
Make sure to trigger meta-data generation so that IDE assistance is available for your keys as well. You may want to review the generated meta-data (META-INF/spring-configuration-metadata.json) to make sure your keys are properly documented.
41.4.2 Autoconfigure module
The autoconfigure module contains everything that is necessary to get started with the library. It may also contain configuration keys definition (@ConfigurationProperties) and any callback interface that can be used to further customize how the components are initialized.
| You should mark the dependencies to the library as optional so that you can include the autoconfigure module in your projects more easily. If you do it that way, the library won’t be provided and Spring Boot will back off by default. |
41.4.3 Starter module
The starter is an empty jar, really. Its only purpose is to provide the necessary dependencies to work with the library; see it as an opinionated view of what is required to get started.
Do not make assumptions about the project in which your starter is added. If the library you are auto-configuring typically requires other starters, mention them as well. Providing a proper set of default dependencies may be hard if the number of optional dependencies is high as you should avoid bringing unnecessary dependencies for a typical usage of the library.
42. WebSockets
Spring Boot provides WebSockets auto-configuration for embedded Tomcat (8 and 7), Jetty 9 and Undertow. If you’re deploying a war file to a standalone container, Spring Boot assumes that the container will be responsible for the configuration of its WebSocket support.
Spring Framework provides rich WebSocket support that can be easily accessed via the spring-boot-starter-websocket module.
43. What to read next
If you want to learn more about any of the classes discussed in this section you can check out the Spring Boot API documentation or you can browse thesource code directly. If you have specific questions, take a look at the how-to section.
If you are comfortable with Spring Boot’s core features, you can carry on and read about production-ready features.
Part V. Spring Boot Actuator: Production-ready features
Spring Boot includes a number of additional features to help you monitor and manage your application when it’s pushed to production. You can choose to manage and monitor your application using HTTP endpoints, with JMX or even by remote shell (SSH or Telnet). Auditing, health and metrics gathering can be automatically applied to your application.
Actuator HTTP endpoints are only available with a Spring MVC-based application. In particular, it will not work with Jersey unless you enable Spring MVC as well.
44. Enabling production-ready features
The spring-boot-actuator module provides all of Spring Boot’s production-ready features. The simplest way to enable the features is to add a dependency to the spring-boot-starter-actuator ‘Starter POM’.
Definition of Actuator
An actuator is a manufacturing term, referring to a mechanical device for moving or controlling something. Actuators can generate a large amount of motion from a small change.
To add the actuator to a Maven based project, add the following ‘starter’ dependency:
For Gradle, use the declaration:
dependencies {
compile("org.springframework.boot:spring-boot-starter-actuator")
}45. Endpoints
Actuator endpoints allow you to monitor and interact with your application. Spring Boot includes a number of built-in endpoints and you can also add your own. For example the health endpoint provides basic application health information.
The way that endpoints are exposed will depend on the type of technology that you choose. Most applications choose HTTP monitoring, where the ID of the endpoint is mapped to a URL. For example, by default, the health endpoint will be mapped to /health.
The following endpoints are available:
| ID | Description | Sensitive Default |
|---|---|---|
|
|
Provides a hypermedia-based “discovery page” for the other endpoints. Requires Spring HATEOAS to be on the classpath. |
true |
|
|
Displays an auto-configuration report showing all auto-configuration candidates and the reason why they ‘were’ or ‘were not’ applied. |
true |
|
|
Displays a complete list of all the Spring beans in your application. |
true |
|
|
Displays a collated list of all |
true |
|
|
Displays documentation, including example requests and responses, for the Actuator’s endpoints. Requires |
false |
|
|
Performs a thread dump. |
true |
|
|
Exposes properties from Spring’s |
true |
|
|
Shows any Flyway database migrations that have been applied. |
true |
|
|
Shows application health information (when the application is secure, a simple ‘status’ when accessed over an unauthenticated connection or full message details when authenticated). |
false |
|
|
Displays arbitrary application info. |
false |
|
|
Shows any Liquibase database migrations that have been applied. |
true |
|
|
Returns the contents of the logfile (if |
true |
|
|
Shows ‘metrics’ information for the current application. |
true |
|
|
Displays a collated list of all |
true |
|
|
Allows the application to be gracefully shutdown (not enabled by default). |
true |
|
|
Displays trace information (by default the last few HTTP requests). |
true |
| Depending on how an endpoint is exposed, the |
45.1 Customizing endpoints
Endpoints can be customized using Spring properties. You can change if an endpoint is enabled, if it is considered sensitive and even its id.
For example, here is an application.properties that changes the sensitivity and id of the beans endpoint and also enables shutdown.
endpoints.beans.id=springbeans
endpoints.beans.sensitive=false
endpoints.shutdown.enabled=true| The prefix ‟ |
By default, all endpoints except for shutdown are enabled. If you prefer to specifically “opt-in” endpoint enablement you can use the endpoints.enabledproperty. For example, the following will disable all endpoints except for info:
endpoints.enabled=false
endpoints.info.enabled=trueLikewise, you can also choose to globally set the “sensitive” flag of all endpoints. By default, the sensitive flag depends on the type of endpoint (see the table above). For example, to mark all endpoints as sensitive except info:
endpoints.sensitive=true
endpoints.info.sensitive=false45.2 Hypermedia for actuator MVC endpoints
If Spring HATEOAS is on the classpath (e.g. through the spring-boot-starter-hateoas or if you are using Spring Data REST) then the HTTP endpoints from the Actuator are enhanced with hypermedia links, and a “discovery page” is added with links to all the endpoints. The “discovery page” is available on /actuator by default. It is implemented as an endpoint, allowing properties to be used to configure its path (endpoints.actuator.path) and whether or not it is enabled (endpoints.actuator.enabled).
When a custom management context path is configured, the “discovery page” will automatically move from /actuator to the root of the management context. For example, if the management context path is /management then the discovery page will be available from /management.
If the HAL Browser is on the classpath via its webjar (org.webjars:hal-browser), or via the spring-data-rest-hal-browser then an HTML “discovery page”, in the form of the HAL Browser, is also provided.
45.3 CORS support
Cross-origin resource sharing (CORS) is a W3C specification that allows you to specify in a flexible way what kind of cross domain requests are authorized. Actuator’s MVC endpoints can be configured to support such scenarios.
CORS support is disabled by default and is only enabled once the endpoints.cors.allowed-origins property has been set. The configuration below permits GET and POST calls from the example.com domain:
endpoints.cors.allowed-origins=http://example.com
endpoints.cors.allowed-methods=GET,POST| Check EndpointCorsProperties for a complete list of options. |
45.4 Adding custom endpoints
If you add a @Bean of type Endpoint then it will automatically be exposed over JMX and HTTP (if there is an server available). An HTTP endpoints can be customized further by creating a bean of type MvcEndpoint. Your MvcEndpoint is not a @Controller but it can use @RequestMapping (and @Managed*) to expose resources.
| If you are doing this as a library feature consider adding a configuration class annoated with |
45.5 Health information
Health information can be used to check the status of your running application. It is often used by monitoring software to alert someone if a production system goes down. The default information exposed by the health endpoint depends on how it is accessed. For an unauthenticated connection in a secure application a simple ‘status’ message is returned, and for an authenticated connection additional details are also displayed (see Section 46.6, “HTTP health endpoint access restrictions” for HTTP details).
Health information is collected from all HealthIndicator beans defined in your ApplicationContext. Spring Boot includes a number of auto-configuredHealthIndicators and you can also write your own.
45.6 Security with HealthIndicators
Information returned by HealthIndicators is often somewhat sensitive in nature. For example, you probably don’t want to publish details of your database server to the world. For this reason, by default, only the health status is exposed over an unauthenticated HTTP connection. If you are happy for complete health information to always be exposed you can set endpoints.health.sensitive to false.
Health responses are also cached to prevent “denial of service” attacks. Use the endpoints.health.time-to-live property if you want to change the default cache period of 1000 milliseconds.
45.6.1 Auto-configured HealthIndicators
The following HealthIndicators are auto-configured by Spring Boot when appropriate:
| Name | Description |
|---|---|
|
|
Checks that a Cassandra database is up. |
|
|
Checks for low disk space. |
|
|
Checks that a connection to |
|
|
Checks that an ElasticSearch cluster is up. |
|
|
Checks that a JMS broker is up. |
|
|
Checks that a mail server is up. |
|
|
Checks that a Mongo database is up. |
|
|
Checks that a Rabbit server is up. |
|
|
Checks that a Redis server is up. |
|
|
Checks that a Solr server is up. |
| It is possible to disable them all using the |
45.6.2 Writing custom HealthIndicators
To provide custom health information you can register Spring beans that implement the HealthIndicator interface. You need to provide an implementation of the health() method and return a Health response. The Health response should include a status and can optionally include additional details to be displayed.
import org.springframework.boot.actuate.health.Health;
import org.springframework.boot.actuate.health.HealthIndicator;
import org.springframework.stereotype.Component;
@Component
public class MyHealthIndicator implements HealthIndicator {
@Override
public Health health() {
int errorCode = check(); // perform some specific health check
if (errorCode != 0) {
return Health.down().withDetail("Error Code", errorCode).build();
}
return Health.up().build();
}
}| The identifier for a given |
In addition to Spring Boot’s predefined Status types, it is also possible for Health to return a custom Status that represents a new system state. In such cases a custom implementation of the HealthAggregator interface also needs to be provided, or the default implementation has to be configured using the management.health.status.order configuration property.
For example, assuming a new Status with code FATAL is being used in one of your HealthIndicator implementations. To configure the severity order add the following to your application properties:
management.health.status.order=DOWN, OUT_OF_SERVICE, UNKNOWN, UPYou might also want to register custom status mappings with the HealthMvcEndpoint if you access the health endpoint over HTTP. For example you could map FATAL to HttpStatus.SERVICE_UNAVAILABLE.
45.7 Custom application info information
You can customize the data exposed by the info endpoint by setting info.* Spring properties. All Environment properties under the info key will be automatically exposed. For example, you could add the following to your application.properties:
info.app.name=MyService
info.app.description=My awesome service
info.app.version=1.0.045.7.1 Automatically expand info properties at build time
Rather than hardcoding some properties that are also specified in your project’s build configuration, you can automatically expand info properties using the existing build configuration instead. This is possible in both Maven and Gradle.
Automatic property expansion using Maven
You can automatically expand info properties from the Maven project using resource filtering. If you use the spring-boot-starter-parent you can then refer to your Maven ‘project properties’ via @..@ placeholders, e.g.
project.artifactId=myproject
project.name=Demo
project.version=X.X.X.X
project.description=Demo project for info endpoint
info.build.artifact[email protected]@
info.build.name[email protected]@
info.build.description[email protected]@
info.build.version[email protected]@| The |
If you don’t use the starter parent, in your pom.xml you need (inside the
and (inside
| The |
Automatic property expansion using Gradle
You can automatically expand info properties from the Gradle project by configuring the Java plugin’s processResources task to do so:
processResources {
expand(project.properties)
}You can then refer to your Gradle project’s properties via placeholders, e.g.
info.build.name=${name}
info.build.description=${description}
info.build.version=${version}| Gradle’s |
45.7.2 Git commit information
Another useful feature of the info endpoint is its ability to publish information about the state of your git source code repository when the project was built. If a git.properties file is contained in your jar the git.branch and git.commit properties will be loaded.
For Maven users the spring-boot-starter-parent POM includes a pre-configured plugin to generate a git.properties file. Simply add the following declaration to your POM:
Gradle users can achieve the same result using the gradle-git-properties plugin
plugins {
id "com.gorylenko.gradle-git-properties" version "1.4.6"
}46. Monitoring and management over HTTP
If you are developing a Spring MVC application, Spring Boot Actuator will auto-configure all enabled endpoints to be exposed over HTTP. The default convention is to use the id of the endpoint as the URL path. For example, health is exposed as /health.
46.1 Securing sensitive endpoints
If you add ‘Spring Security’ to your project, all sensitive endpoints exposed over HTTP will be protected. By default ‘basic’ authentication will be used with the username user and a generated password (which is printed on the console when the application starts).
| Generated passwords are logged as the application starts. Search for ‘Using default security password’. |
You can use Spring properties to change the username and password and to change the security role required to access the endpoints. For example, you might set the following in your application.properties:
security.user.name=admin
security.user.password=secret
management.security.role=SUPERUSER| If you don’t use Spring Security and your HTTP endpoints are exposed publicly, you should carefully consider which endpoints you enable. SeeSection 45.1, “Customizing endpoints” for details of how you can set |
46.2 Customizing the management endpoint paths
Sometimes it is useful to group all management endpoints under a single path. For example, your application might already use /info for another purpose. You can use the management.context-path property to set a prefix for your management endpoint:
management.context-path=/manageThe application.properties example above will change the endpoint from /{id} to /manage/{id} (e.g. /manage/info).
You can also change the “id” of an endpoint (using endpoints.{name}.id) which then changes the default resource path for the MVC endpoint. Legal endpoint ids are composed only of alphanumeric characters (because they can be exposed in a number of places, including JMX object names, where special characters are forbidden). The MVC path can be changed separately by configuring endpoints.{name}.path, and there is no validation on those values (so you can use anything that is legal in a URL path). For example, to change the location of the /health endpoint to /ping/me you can setendpoints.health.path=/ping/me.
| If you provide a custom |
46.3 Customizing the management server port
Exposing management endpoints using the default HTTP port is a sensible choice for cloud based deployments. If, however, your application runs inside your own data center you may prefer to expose endpoints using a different HTTP port.
The management.port property can be used to change the HTTP port.
management.port=8081Since your management port is often protected by a firewall, and not exposed to the public you might not need security on the management endpoints, even if your main application is secure. In that case you will have Spring Security on the classpath, and you can disable management security like this:
management.security.enabled=false(If you don’t have Spring Security on the classpath then there is no need to explicitly disable the management security in this way, and it might even break the application.)
46.4 Customizing the management server address
You can customize the address that the management endpoints are available on by setting the management.address property. This can be useful if you want to listen only on an internal or ops-facing network, or to only listen for connections from localhost.
| You can only listen on a different address if the port is different to the main server port. |
Here is an example application.properties that will not allow remote management connections:
management.port=8081
management.address=127.0.0.146.5 Disabling HTTP endpoints
If you don’t want to expose endpoints over HTTP you can set the management port to -1:
management.port=-146.6 HTTP health endpoint access restrictions
The information exposed by the health endpoint varies depending on whether or not it’s accessed anonymously, and whether or not the enclosing application is secure. By default, when accessed anonymously in a secure application, any details about the server’s health are hidden and the endpoint will simply indicate whether or not the server is up or down. Furthermore the response is cached for a configurable period to prevent the endpoint being used in a denial of service attack. The endpoints.health.time-to-live property is used to configure the caching period in milliseconds. It defaults to 1000, i.e. one second.
The above-described restrictions can be enhanced, thereby allowing only authenticated users full access to the health endpoint in a secure application. To do so, set endpoints.health.sensitive to true. Here’s a summary of behavior (with default sensitive flag value “false” indicated in bold):
management.security.enabled |
endpoints.health.sensitive |
Unauthenticated | Authenticated |
|---|---|---|---|
| false |
false |
Full content |
Full content |
| false |
true |
Status only |
Full content |
| true |
false |
Status only |
Full content |
| true |
true |
No content |
Full content |
47. Monitoring and management over JMX
Java Management Extensions (JMX) provide a standard mechanism to monitor and manage applications. By default Spring Boot will expose management endpoints as JMX MBeans under the org.springframework.boot domain.
47.1 Customizing MBean names
The name of the MBean is usually generated from the id of the endpoint. For example the health endpoint is exposed as org.springframework.boot/Endpoint/healthEndpoint.
If your application contains more than one Spring ApplicationContext you may find that names clash. To solve this problem you can set the endpoints.jmx.unique-names property to true so that MBean names are always unique.
You can also customize the JMX domain under which endpoints are exposed. Here is an example application.properties:
endpoints.jmx.domain=myapp
endpoints.jmx.unique-names=true47.2 Disabling JMX endpoints
If you don’t want to expose endpoints over JMX you can set the endpoints.jmx.enabled property to false:
endpoints.jmx.enabled=false47.3 Using Jolokia for JMX over HTTP
Jolokia is a JMX-HTTP bridge giving an alternative method of accessing JMX beans. To use Jolokia, simply include a dependency to org.jolokia:jolokia-core. For example, using Maven you would add the following:
Jolokia can then be accessed using /jolokia on your management HTTP server.
47.3.1 Customizing Jolokia
Jolokia has a number of settings that you would traditionally configure using servlet parameters. With Spring Boot you can use your application.properties, simply prefix the parameter with jolokia.config.:
jolokia.config.debug=true47.3.2 Disabling Jolokia
If you are using Jolokia but you don’t want Spring Boot to configure it, simply set the endpoints.jolokia.enabled property to false:
endpoints.jolokia.enabled=false48. Monitoring and management using a remote shell
Spring Boot supports an integrated Java shell called ‘CRaSH’. You can use CRaSH to ssh or telnet into your running application. To enable remote shell support, add the following dependency to your project:
| If you want to also enable telnet access you will additionally need a dependency on |
| CRaSH requires to run with a JDK as it compiles commands on the fly. If a basic |
48.1 Connecting to the remote shell
By default the remote shell will listen for connections on port 2000. The default user is user and the default password will be randomly generated and displayed in the log output. If your application is using Spring Security, the shell will use the same configuration by default. If not, a simple authentication will be applied and you should see a message like this:
Using default password for shell access: ec03e16c-4cf4-49ee-b745-7c8255c1dd7eLinux and OSX users can use ssh to connect to the remote shell, Windows users can download and install PuTTY.
$ ssh -p 2000 user@localhost
user@localhost's password:
. ____ _ __ _ _
/\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
\\/ ___)| |_)| | | | | || (_| | ) ) ) )
' |____| .__|_| |_|_| |_\__, | / / / /
=========|_|==============|___/=/_/_/_/
:: Spring Boot :: (v1.3.7.RELEASE) on myhostType help for a list of commands. Spring Boot provides metrics, beans, autoconfig and endpoint commands.
48.1.1 Remote shell credentials
You can use the shell.auth.simple.user.name and shell.auth.simple.user.password properties to configure custom connection credentials. It is also possible to use a ‘Spring Security’ AuthenticationManager to handle login duties. See the CrshAutoConfiguration and ShellProperties Javadoc for full details.
48.2 Extending the remote shell
The remote shell can be extended in a number of interesting ways.
48.2.1 Remote shell commands
You can write additional shell commands using Groovy or Java (see the CRaSH documentation for details). By default Spring Boot will search for commands in the following locations:
classpath*:/commands/**classpath*:/crash/commands/**
| You can change the search path by settings a |
Here is a simple ‘hello’ command that could be loaded from src/main/resources/commands/hello.groovy
package commands
import org.crsh.cli.Command
import org.crsh.cli.Usage
import org.crsh.command.InvocationContext
class hello {
@Usage("Say Hello")
@Command
def main(InvocationContext context) {
return "Hello"
}
}Spring Boot adds some additional attributes to InvocationContext that you can access from your command:
| Attribute Name | Description |
|---|---|
|
|
The version of Spring Boot |
|
|
The version of the core Spring Framework |
|
|
Access to the Spring |
|
|
Access to the Spring |
48.2.2 Remote shell plugins
In addition to new commands, it is also possible to extend other CRaSH shell features. All Spring Beans that extend org.crsh.plugin.CRaSHPlugin will be automatically registered with the shell.
For more information please refer to the CRaSH reference documentation.
49. Metrics
Spring Boot Actuator includes a metrics service with ‘gauge’ and ‘counter’ support. A ‘gauge’ records a single value; and a ‘counter’ records a delta (an increment or decrement). Spring Boot Actuator also provides a PublicMetrics interface that you can implement to expose metrics that you cannot record via one of those two mechanisms. Look at SystemPublicMetrics for an example.
Metrics for all HTTP requests are automatically recorded, so if you hit the metrics endpoint you should see a response similar to this:
{
"counter.status.200.root": 20,
"counter.status.200.metrics": 3,
"counter.status.200.star-star": 5,
"counter.status.401.root": 4,
"gauge.response.star-star": 6,
"gauge.response.root": 2,
"gauge.response.metrics": 3,
"classes": 5808,
"classes.loaded": 5808,
"classes.unloaded": 0,
"heap": 3728384,
"heap.committed": 986624,
"heap.init": 262144,
"heap.used": 52765,
"nonheap": 0,
"nonheap.committed": 77568,
"nonheap.init": 2496,
"nonheap.used": 75826,
"mem": 986624,
"mem.free": 933858,
"processors": 8,
"threads": 15,
"threads.daemon": 11,
"threads.peak": 15,
"threads.totalStarted": 42,
"uptime": 494836,
"instance.uptime": 489782,
"datasource.primary.active": 5,
"datasource.primary.usage": 0.25
}Here we can see basic memory, heap, class loading, processor and thread pool information along with some HTTP metrics. In this instance the root (‘/’) and /metrics URLs have returned HTTP 200 responses 20 and 3 times respectively. It also appears that the root URL returned HTTP 401(unauthorized) 4 times. The double asterisks (star-star) comes from a request matched by Spring MVC as /** (normally a static resource).
The gauge shows the last response time for a request. So the last request to root took 2ms to respond and the last to /metrics took 3ms.
| In this example we are actually accessing the endpoint over HTTP using the |
49.1 System metrics
The following system metrics are exposed by Spring Boot:
- The total system memory in KB (
mem) - The amount of free memory in KB (
mem.free) - The number of processors (
processors) - The system uptime in milliseconds (
uptime) - The application context uptime in milliseconds (
instance.uptime) - The average system load (
systemload.average) - Heap information in KB (
heap,heap.committed,heap.init,heap.used) - Thread information (
threads,thread.peak,thread.daemon) - Class load information (
classes,classes.loaded,classes.unloaded) - Garbage collection information (
gc.xxx.count,gc.xxx.time)
49.2 DataSource metrics
The following metrics are exposed for each supported DataSource defined in your application:
- The number of active connections (
datasource.xxx.active) - The current usage of the connection pool (
datasource.xxx.usage).
All data source metrics share the datasource. prefix. The prefix is further qualified for each data source:
- If the data source is the primary data source (that is either the only available data source or the one flagged
@Primaryamongst the existing ones), the prefix isdatasource.primary. - If the data source bean name ends with
DataSource, the prefix is the name of the bean withoutDataSource(i.e.datasource.batchforbatchDataSource). - In all other cases, the name of the bean is used.
It is possible to override part or all of those defaults by registering a bean with a customized version of DataSourcePublicMetrics. By default, Spring Boot provides metadata for all supported data sources; you can add additional DataSourcePoolMetadataProvider beans if your favorite data source isn’t supported out of the box. See DataSourcePoolMetadataProvidersConfiguration for examples.
49.3 Cache metrics
The following metrics are exposed for each supported cache defined in your application:
- The current size of the cache (
cache.xxx.size) - Hit ratio (
cache.xxx.hit.ratio) - Miss ratio (
cache.xxx.miss.ratio)
| Cache providers do not expose the hit/miss ratio in a consistent way. While some expose an aggregated value (i.e. the hit ratio since the last time the stats were cleared), others expose a temporal value (i.e. the hit ratio of the last second). Check your caching provider documentation for more details. |
If two different cache managers happen to define the same cache, the name of the cache is prefixed by the name of the CacheManager bean.
It is possible to override part or all of those defaults by registering a bean with a customized version of CachePublicMetrics. By default, Spring Boot provides cache statistics for EhCache, Hazelcast, Infinispan, JCache and Guava. You can add additional CacheStatisticsProvider beans if your favorite caching library isn’t supported out of the box. See CacheStatisticsAutoConfiguration for examples.
49.4 Tomcat session metrics
If you are using Tomcat as your embedded servlet container, session metrics will automatically be exposed. The httpsessions.active and httpsessions.max keys provide the number of active and maximum sessions.
49.5 Recording your own metrics
To record your own metrics inject a CounterService and/or GaugeService into your bean. The CounterService exposes increment, decrement and reset methods; the GaugeService provides a submit method.
Here is a simple example that counts the number of times that a method is invoked:
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.actuate.metrics.CounterService;
import org.springframework.stereotype.Service;
@Service
public class MyService {
private final CounterService counterService;
@Autowired
public MyService(CounterService counterService) {
this.counterService = counterService;
}
public void exampleMethod() {
this.counterService.increment("services.system.myservice.invoked");
}
}| You can use any string as a metric name but you should follow guidelines of your chosen store/graphing technology. Some good guidelines for Graphite are available on Matt Aimonetti’s Blog. |
49.6 Adding your own public metrics
To add additional metrics that are computed every time the metrics endpoint is invoked, simply register additional PublicMetrics implementation bean(s). By default, all such beans are gathered by the endpoint. You can easily change that by defining your own MetricsEndpoint.
49.7 Special features with Java 8
The default implementation of GaugeService and CounterService provided by Spring Boot depends on the version of Java that you are using. With Java 8 (or better) the implementation switches to a high-performance version optimized for fast writes, backed by atomic in-memory buffers, rather than by the immutable but relatively expensive Metric type (counters are approximately 5 times faster and gauges approximately twice as fast as the repository-based implementations). The Dropwizard metrics services (see below) are also very efficient even for Java 7 (they have backports of some of the Java 8 concurrency libraries), but they do not record timestamps for metric values. If performance of metric gathering is a concern then it is always advisable to use one of the high-performance options, and also to only read metrics infrequently, so that the writes are buffered locally and only read when needed.
| The old |
49.8 Metric writers, exporters and aggregation
Spring Boot provides a couple of implementations of a marker interface called Exporter which can be used to copy metric readings from the in-memory buffers to a place where they can be analyzed and displayed. Indeed, if you provide a @Bean that implements the MetricWriter interface (or GaugeWriterfor simple use cases) and mark it @ExportMetricWriter, then it will automatically be hooked up to an Exporter and fed metric updates every 5 seconds (configured via spring.metrics.export.delay-millis). In addition, any MetricReader that you define and mark as @ExportMetricReader will have its values exported by the default exporter.
The default exporter is a MetricCopyExporter which tries to optimize itself by not copying values that haven’t changed since it was last called (the optimization can be switched off using a flag spring.metrics.export.send-latest). Note also that the Dropwizard MetricRegistry has no support for timestamps, so the optimization is not available if you are using Dropwizard metrics (all metrics will be copied on every tick).
The default values for the export trigger (delay-millis, includes, excludes and send-latest) can be set as spring.metrics.export.*. Individual values for specific MetricWriters can be set as spring.metrics.export.triggers. where
| The automatic export of metrics is disabled if you switch off the default |
49.8.1 Example: Export to Redis
If you provide a @Bean of type RedisMetricRepository and mark it @ExportMetricWriter the metrics are exported to a Redis cache for aggregation. The RedisMetricRepository has two important parameters to configure it for this purpose: prefix and key (passed into its constructor). It is best to use a prefix that is unique to the application instance (e.g. using a random value and maybe the logical name of the application to make it possible to correlate with other instances of the same application). The “key” is used to keep a global index of all metric names, so it should be unique “globally”, whatever that means for your system (e.g. two instances of the same system could share a Redis cache if they have distinct keys).
Example:
@Bean
@ExportMetricWriter
MetricWriter metricWriter(MetricExportProperties export) {
return new RedisMetricRepository(connectionFactory,
export.getRedis().getPrefix(), export.getRedis().getKey());
}application.properties.
spring.metrics.export.redis.prefix: metrics.mysystem.${spring.application.name:application}.${random.value:0000}
spring.metrics.export.redis.key: keys.metrics.mysystem
The prefix is constructed with the application name and id at the end, so it can easily be used to identify a group of processes with the same logical name later.
| It’s important to set both the |
| The example above uses |
49.8.2 Example: Export to Open TSDB
If you provide a @Bean of type OpenTsdbGaugeWriter and mark it @ExportMetricWriter metrics are exported to Open TSDB for aggregation. The OpenTsdbGaugeWriter has a url property that you need to set to the Open TSDB “/put” endpoint, e.g. localhost:4242/api/put). It also has anamingStrategy that you can customize or configure to make the metrics match the data structure you need on the server. By default it just passes through the metric name as an Open TSDB metric name, and adds the tags “domain” (with value “org.springframework.metrics”) and “process” (with the value equal to the object hash of the naming strategy). Thus, after running the application and generating some metrics you can inspect the metrics in the TSD UI (localhost:4242 by default).
Example:
curl localhost:4242/api/query?start=1h-ago&m=max:counter.status.200.root
[
{
"metric": "counter.status.200.root",
"tags": {
"domain": "org.springframework.metrics",
"process": "b968a76"
},
"aggregateTags": [],
"dps": {
"1430492872": 2,
"1430492875": 6
}
}
]49.8.3 Example: Export to Statsd
To export metrics to Statsd, make sure first that you have added com.timgroup:java-statsd-client as a dependency of your project (Spring Boot provides a dependency management for it). Then add a spring.metrics.export.statsd.host value to your application.properties file. Connections will be opened to port 8125 unless a spring.metrics.export.statsd.port override is provided. You can use spring.metrics.export.statsd.prefix if you want a custom prefix.
Alternatively, you can provide a @Bean of type StatsdMetricWriter and mark it @ExportMetricWriter:
@Value("${spring.application.name:application}.${random.value:0000}")
private String prefix = "metrics";
@Bean
@ExportMetricWriter
MetricWriter metricWriter() {
return new StatsdMetricWriter(prefix, "localhost", "8125");
}49.8.4 Example: Export to JMX
If you provide a @Bean of type JmxMetricWriter marked @ExportMetricWriter the metrics are exported as MBeans to the local server (the MBeanExporter is provided by Spring Boot JMX auto-configuration as long as it is switched on). Metrics can then be inspected, graphed, alerted etc. using any tool that understands JMX (e.g. JConsole or JVisualVM).
Example:
@Bean
@ExportMetricWriter
MetricWriter metricWriter(MBeanExporter exporter) {
return new JmxMetricWriter(exporter);
}Each metric is exported as an individual MBean. The format for the ObjectNames is given by an ObjectNamingStrategy which can be injected into the JmxMetricWriter (the default breaks up the metric name and tags the first two period-separated sections in a way that should make the metrics group nicely in JVisualVM or JConsole).
49.9 Aggregating metrics from multiple sources
There is an AggregateMetricReader that you can use to consolidate metrics from different physical sources. Sources for the same logical metric just need to publish them with a period-separated prefix, and the reader will aggregate (by truncating the metric names, and dropping the prefix). Counters are summed and everything else (i.e. gauges) take their most recent value.
This is very useful if multiple application instances are feeding to a central (e.g. Redis) repository and you want to display the results. Particularly recommended in conjunction with a MetricReaderPublicMetrics for hooking up to the results to the “/metrics” endpoint.
Example:
@Autowired
private MetricExportProperties export;
@Bean
public PublicMetrics metricsAggregate() {
return new MetricReaderPublicMetrics(aggregatesMetricReader());
}
private MetricReader globalMetricsForAggregation() {
return new RedisMetricRepository(this.connectionFactory,
this.export.getRedis().getAggregatePrefix(), this.export.getRedis().getKey());
}
private MetricReader aggregatesMetricReader() {
AggregateMetricReader repository = new AggregateMetricReader(
globalMetricsForAggregation());
return repository;
}| The example above uses |
| The |
49.10 Dropwizard Metrics
A default MetricRegistry Spring bean will be created when you declare a dependency to the io.dropwizard.metrics:metrics-core library; you can also register you own @Bean instance if you need customizations. Users of the Dropwizard ‘Metrics’ library will find that Spring Boot metrics are automatically published to com.codahale.metrics.MetricRegistry. Metrics from the MetricRegistry are also automatically exposed via the /metrics endpoint
When Dropwizard metrics are in use, the default CounterService and GaugeService are replaced with a DropwizardMetricServices, which is a wrapper around the MetricRegistry (so you can @Autowired one of those services and use it as normal). You can also create “special” Dropwizard metrics by prefixing your metric names with the appropriate type (i.e. timer.*, histogram.* for gauges, and meter.* for counters).
49.11 Message channel integration
If a MessageChannel bean called metricsChannel exists, then a MetricWriter will be created that writes metrics to that channel. The writer is automatically hooked up to an exporter (as for all writers), so all metric values will appear on the channel, and additional analysis or actions can be taken by subscribers (it’s up to you to provide the channel and any subscribers you need).
50. Auditing
Spring Boot Actuator has a flexible audit framework that will publish events once Spring Security is in play (‘authentication success’, ‘failure’ and ‘access denied’ exceptions by default). This can be very useful for reporting, and also to implement a lock-out policy based on authentication failures. To customize published security events you can provide your own implementations of AbstractAuthenticationAuditListener and AbstractAuthorizationAuditListener.
You can also choose to use the audit services for your own business events. To do that you can either inject the existing AuditEventRepository into your own components and use that directly, or you can simply publish AuditApplicationEvent via the Spring ApplicationEventPublisher (using ApplicationEventPublisherAware).
51. Tracing
Tracing is automatically enabled for all HTTP requests. You can view the trace endpoint and obtain basic information about the last few requests:
[{
"timestamp": 1394343677415,
"info": {
"method": "GET",
"path": "/trace",
"headers": {
"request": {
"Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8",
"Connection": "keep-alive",
"Accept-Encoding": "gzip, deflate",
"User-Agent": "Mozilla/5.0 Gecko/Firefox",
"Accept-Language": "en-US,en;q=0.5",
"Cookie": "_ga=GA1.1.827067509.1390890128; ..."
"Authorization": "Basic ...",
"Host": "localhost:8080"
},
"response": {
"Strict-Transport-Security": "max-age=31536000 ; includeSubDomains",
"X-Application-Context": "application:8080",
"Content-Type": "application/json;charset=UTF-8",
"status": "200"
}
}
}
},{
"timestamp": 1394343684465,
...
}]51.1 Custom tracing
If you need to trace additional events you can inject a TraceRepository into your Spring beans. The add method accepts a single Map structure that will be converted to JSON and logged.
By default an InMemoryTraceRepository will be used that stores the last 100 events. You can define your own instance of the InMemoryTraceRepositorybean if you need to expand the capacity. You can also create your own alternative TraceRepository implementation if needed.
52. Process monitoring
In Spring Boot Actuator you can find a couple of classes to create files that are useful for process monitoring:
ApplicationPidFileWritercreates a file containing the application PID (by default in the application directory with the file nameapplication.pid).EmbeddedServerPortFileWritercreates a file (or files) containing the ports of the embedded server (by default in the application directory with the file nameapplication.port).
These writers are not activated by default, but you can enable them in one of the ways described below.
52.1 Extend configuration
In META-INF/spring.factories file you can activate the listener(s) that writes a PID file. Example:
org.springframework.context.ApplicationListener=\
org.springframework.boot.actuate.system.ApplicationPidFileWriter,
org.springframework.boot.actuate.system.EmbeddedServerPortFileWriter52.2 Programmatically
You can also activate a listener by invoking the SpringApplication.addListeners(…) method and passing the appropriate Writer object. This method also allows you to customize the file name and path via the Writer constructor.
53. What to read next
If you want to explore some of the concepts discussed in this chapter, you can take a look at the actuator sample applications. You also might want to read about graphing tools such as Graphite.
Otherwise, you can continue on, to read about ‘deployment options’ or jump ahead for some in-depth information about Spring Boot’s build tool plugins.
Part VI. Deploying Spring Boot applications
Spring Boot’s flexible packaging options provide a great deal of choice when it comes to deploying your application. You can easily deploy Spring Boot applications to a variety of cloud platforms, to a container images (such as Docker) or to virtual/real machines.
This section covers some of the more common deployment scenarios.
54. Deploying to the cloud
Spring Boot’s executable jars are ready-made for most popular cloud PaaS (platform-as-a-service) providers. These providers tend to require that you “bring your own container”; they manage application processes (not Java applications specifically), so they need some intermediary layer that adapts your application to the cloud’s notion of a running process.
Two popular cloud providers, Heroku and Cloud Foundry, employ a “buildpack” approach. The buildpack wraps your deployed code in whatever is needed to start your application: it might be a JDK and a call to java, it might be an embedded web server, or it might be a full-fledged application server. A buildpack is pluggable, but ideally you should be able to get by with as few customizations to it as possible. This reduces the footprint of functionality that is not under your control. It minimizes divergence between development and production environments.
Ideally, your application, like a Spring Boot executable jar, has everything that it needs to run packaged within it.
In this section we’ll look at what it takes to get the simple application that we developed in the “Getting Started” section up and running in the Cloud.
54.1 Cloud Foundry
Cloud Foundry provides default buildpacks that come into play if no other buildpack is specified. The Cloud Foundry Java buildpack has excellent support for Spring applications, including Spring Boot. You can deploy stand-alone executable jar applications, as well as traditional .war packaged applications.
Once you’ve built your application (using, for example, mvn clean package) and installed the cf command line tool, simply deploy your application using the cf push command as follows, substituting the path to your compiled .jar. Be sure to have logged in with your cf command line client before pushing an application.
$ cf push acloudyspringtime -p target/demo-0.0.1-SNAPSHOT.jarSee the cf push documentation for more options. If there is a Cloud Foundry manifest.yml file present in the same directory, it will be consulted.
| Here we are substituting |
At this point cf will start uploading your application:
Uploading acloudyspringtime... OK
Preparing to start acloudyspringtime... OK
-----> Downloaded app package (8.9M)
-----> Java Buildpack source: system
-----> Downloading Open JDK 1.7.0_51 from .../x86_64/openjdk-1.7.0_51.tar.gz (1.8s)
Expanding Open JDK to .java-buildpack/open_jdk (1.2s)
-----> Downloading Spring Auto Reconfiguration from 0.8.7 .../auto-reconfiguration-0.8.7.jar (0.1s)
-----> Uploading droplet (44M)
Checking status of app 'acloudyspringtime'...
0 of 1 instances running (1 starting)
...
0 of 1 instances running (1 down)
...
0 of 1 instances running (1 starting)
...
1 of 1 instances running (1 running)
App startedCongratulations! The application is now live!
It’s easy to then verify the status of the deployed application:
$ cf apps
Getting applications in ...
OK
name requested state instances memory disk urls
...
acloudyspringtime started 1/1 512M 1G acloudyspringtime.cfapps.io
...Once Cloud Foundry acknowledges that your application has been deployed, you should be able to hit the application at the URI given, in this caseacloudyspringtime.cfapps.io/.
54.1.1 Binding to services
By default, metadata about the running application as well as service connection information is exposed to the application as environment variables (for example: $VCAP_SERVICES). This architecture decision is due to Cloud Foundry’s polyglot (any language and platform can be supported as a buildpack) nature; process-scoped environment variables are language agnostic.
Environment variables don’t always make for the easiest API so Spring Boot automatically extracts them and flattens the data into properties that can be accessed through Spring’s Environment abstraction:
@Component
class MyBean implements EnvironmentAware {
private String instanceId;
@Override
public void setEnvironment(Environment environment) {
this.instanceId = environment.getProperty("vcap.application.instance_id");
}
// ...
}All Cloud Foundry properties are prefixed with vcap. You can use vcap properties to access application information (such as the public URL of the application) and service information (such as database credentials). See CloudFoundryVcapEnvironmentPostProcessor Javadoc for complete details.
| The Spring Cloud Connectors project is a better fit for tasks such as configuring a DataSource. Spring Boot includes auto-configuration support and a |
54.2 Heroku
Heroku is another popular PaaS platform. To customize Heroku builds, you provide a Procfile, which provides the incantation required to deploy an application. Heroku assigns a port for the Java application to use and then ensures that routing to the external URI works.
You must configure your application to listen on the correct port. Here’s the Procfile for our starter REST application:
web: java -Dserver.port=$PORT -jar target/demo-0.0.1-SNAPSHOT.jarSpring Boot makes -D arguments available as properties accessible from a Spring Environment instance. The server.port configuration property is fed to the embedded Tomcat, Jetty or Undertow instance which then uses it when it starts up. The $PORT environment variable is assigned to us by the Heroku PaaS.
Heroku by default will use Java 1.8. This is fine as long as your Maven or Gradle build is set to use the same version (Maven users can use the java.version property). If you want to use JDK 1.7, create a new file adjacent to your pom.xml and Procfile, called system.properties. In this file add the following:
java.runtime.version=1.7This should be everything you need. The most common workflow for Heroku deployments is to git push the code to production.
$ git push heroku master
Initializing repository, done.
Counting objects: 95, done.
Delta compression using up to 8 threads.
Compressing objects: 100% (78/78), done.
Writing objects: 100% (95/95), 8.66 MiB | 606.00 KiB/s, done.
Total 95 (delta 31), reused 0 (delta 0)
-----> Java app detected
-----> Installing OpenJDK 1.8... done
-----> Installing Maven 3.3.1... done
-----> Installing settings.xml... done
-----> Executing: mvn -B -DskipTests=true clean install
[INFO] Scanning for projects...
Downloading: http://repo.spring.io/...
Downloaded: http://repo.spring.io/... (818 B at 1.8 KB/sec)
....
Downloaded: http://s3pository.heroku.com/jvm/... (152 KB at 595.3 KB/sec)
[INFO] Installing /tmp/build_0c35a5d2-a067-4abc-a232-14b1fb7a8229/target/...
[INFO] Installing /tmp/build_0c35a5d2-a067-4abc-a232-14b1fb7a8229/pom.xml ...
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 59.358s
[INFO] Finished at: Fri Mar 07 07:28:25 UTC 2014
[INFO] Final Memory: 20M/493M
[INFO] ------------------------------------------------------------------------
-----> Discovering process types
Procfile declares types -> web
-----> Compressing... done, 70.4MB
-----> Launching... done, v6
http://agile-sierra-1405.herokuapp.com/ deployed to Heroku
To [email protected]:agile-sierra-1405.git
* [new branch] master -> masterYour application should now be up and running on Heroku.
54.3 OpenShift
OpenShift is the RedHat public (and enterprise) PaaS solution. Like Heroku, it works by running scripts triggered by git commits, so you can script the launching of a Spring Boot application in pretty much any way you like as long as the Java runtime is available (which is a standard feature you can ask for at OpenShift). To do this you can use the DIY Cartridge and hooks in your repository under .openshift/action_hooks:
The basic model is to:
- Ensure Java and your build tool are installed remotely, e.g. using a
pre_buildhook (Java and Maven are installed by default, Gradle is not) -
Use a
buildhook to build your jar (using Maven or Gradle), e.g.#!/bin/bash cd $OPENSHIFT_REPO_DIR mvn package -s .openshift/settings.xml -DskipTests=true -
Add a
starthook that callsjava -jar …#!/bin/bash cd $OPENSHIFT_REPO_DIR nohup java -jar target/*.jar --server.port=${OPENSHIFT_DIY_PORT} --server.address=${OPENSHIFT_DIY_IP} & -
Use a
stophook (since the start is supposed to return cleanly), e.g.#!/bin/bash source $OPENSHIFT_CARTRIDGE_SDK_BASH PID=$(ps -ef | grep java.*\.jar | grep -v grep | awk '{ print $2 }') if [ -z "$PID" ] then client_result "Application is already stopped" else kill $PID fi -
Embed service bindings from environment variables provided by the platform in your
application.properties, e.g.spring.datasource.url: jdbc:mysql://${OPENSHIFT_MYSQL_DB_HOST}:${OPENSHIFT_MYSQL_DB_PORT}/${OPENSHIFT_APP_NAME} spring.datasource.username: ${OPENSHIFT_MYSQL_DB_USERNAME} spring.datasource.password: ${OPENSHIFT_MYSQL_DB_PASSWORD}
There’s a blog on running Gradle in OpenShift on their website that will get you started with a gradle build to run the app.
54.4 Boxfuse and Amazon Web Services
Boxfuse works by turning your Spring Boot executable jar or war into a minimal VM image that can be deployed unchanged either on VirtualBox or on AWS. Boxfuse comes with deep integration for Spring Boot and will use the information from your Spring Boot configuration file to automatically configure ports and health check URLs. Boxfuse leverages this information both for the images it produces as well as for all the resources it provisions (instances, security groups, elastic load balancers, etc).
Once you have created a Boxfuse account, connected it to your AWS account, and installed the latest version of the Boxfuse Client, you can deploy your Spring Boot application to AWS as follows (ensure the application has been built by Maven or Gradle first using, for example, mvn clean package):
$ boxfuse run myapp-1.0.jar -env=prodSee the boxfuse run documentation for more options. If there is a boxfuse.com/docs/commandline/#configuration [boxfuse.conf] file present in the current directory, it will be consulted.
| By default Boxfuse will activate a Spring profile named |
At this point boxfuse will create an image for your application, upload it, and then configure and start the necessary resources on AWS:
Fusing Image for myapp-1.0.jar ...
Image fused in 00:06.838s (53937 K) -> axelfontaine/myapp:1.0
Creating axelfontaine/myapp ...
Pushing axelfontaine/myapp:1.0 ...
Verifying axelfontaine/myapp:1.0 ...
Creating Elastic IP ...
Mapping myapp-axelfontaine.boxfuse.io to 52.28.233.167 ...
Waiting for AWS to create an AMI for axelfontaine/myapp:1.0 in eu-central-1 (this may take up to 50 seconds) ...
AMI created in 00:23.557s -> ami-d23f38cf
Creating security group boxfuse-sg_axelfontaine/myapp:1.0 ...
Launching t2.micro instance of axelfontaine/myapp:1.0 (ami-d23f38cf) in eu-central-1 ...
Instance launched in 00:30.306s -> i-92ef9f53
Waiting for AWS to boot Instance i-92ef9f53 and Payload to start at http://52.28.235.61/ ...
Payload started in 00:29.266s -> http://52.28.235.61/
Remapping Elastic IP 52.28.233.167 to i-92ef9f53 ...
Waiting 15s for AWS to complete Elastic IP Zero Downtime transition ...
Deployment completed successfully. axelfontaine/myapp:1.0 is up and running at http://myapp-axelfontaine.boxfuse.io/Your application should now be up and running on AWS.
There’s a blog on deploying Spring Boot apps on EC2 as well as documentation for the Boxfuse Spring Boot integration on their website that will get you started with a Maven build to run the app.
54.5 Google App Engine
Google App Engine is tied to the Servlet 2.5 API, so you can’t deploy a Spring Application there without some modifications. See the Servlet 2.5 section of this guide.
55. Installing Spring Boot applications
In additional to running Spring Boot applications using java -jar it is also possible to make fully executable applications for Unix systems. This makes it very easy to install and manage Spring Boot applications in common production environments.
To create a ‘fully executable’ jar with Maven use the following plugin configuration:
With Gradle, the equivalent configuration would be:
apply plugin: 'spring-boot'
springBoot {
executable = true
}| Fully executable jars work by embedding an extra script at the front of the file. Not all tools currently accept this format so you may not always be able to use this technique. |
| The default script supports most Linux distributions and is tested on CentOS and Ubuntu. Other platforms, such as OS X and FreeBSD, will require the use of a custom |
| When a fully executable jar is run, it uses the jar’s directory as the working directory. |
55.1 Unix/Linux services
Spring Boot application can be easily started as Unix/Linux services using either init.d or systemd.
55.1.1 Installation as an init.d service (System V)
The default executable script that can be embedded into Spring Boot jars will act as an init.d script when it is symlinked to /etc/init.d. The standard start, stop, restart and status commands can be used. The script supports the following features:
- Starts the services as the user that owns the jar file
- Tracks application’s PID using
/var/run// .pid - Writes console logs to
/var/log/.log
Assuming that you have a Spring Boot application installed in /var/myapp, to install a Spring Boot application as an init.d service simply create a symlink:
$ sudo ln -s /var/myapp/myapp.jar /etc/init.d/myappOnce installed, you can start and stop the service in the usual way. You can also flag the application to start automatically using your standard operating system tools. For example, if you use Debian:
$ update-rc.d myapp defaults Securing an init.d service
| The following is a set of guidelines on how to secure a Spring Boot application that’s being run as an init.d service. It is not intended to be an exhaustive list of everything that should be done to harden an application and the environment in which it runs. |
When executed as root, as is the case when root is being used to start an init.d service, the default executable script will run the application as the user which owns the jar file. You should never run a Spring Boot application as root so your application’s jar file should never be owned by root. Instead, create a specific user to run your application and use chown to make it the owner of the jar file. For example:
$ chown bootapp:bootapp your-app.jarIn this case, the default executable script will run the application as the bootapp user.
| To reduce the chances of the application’s user account being compromised, you should consider preventing it from using a login shell. Set the account’s shell to |
You should also take steps to prevent the modification of your application’s jar file. Firstly, configure its permissions so that it cannot be written and can only be read or executed by its owner:
$ chmod 500 your-app.jarSecondly, you should also take steps to limit the damage if your application or the account that’s running it is compromised. If an attacker does gain access, they could make the jar file writable and change its contents. One way to protect against this is to make it immutable using chattr:
$ sudo chattr +i your-app.jarThis will prevent any user, including root, from modifying the jar.
If root is used to control the application’s service and you use a .conf file to customize its startup, the .conf file will be read and evaluated by the root user. It should be secured accordingly. Use chmod so that the file can only be read by the owner and use chown to make root the owner:
$ chmod 400 your-app.conf
$ sudo chown root:root your-app.conf55.1.2 Installation as a systemd service
Systemd is the successor of the System V init system, and is now being used by many modern Linux distributions. Although you can continue to use init.dscripts with systemd, it is also possible to launch Spring Boot applications using systemd ‘service’ scripts.
Assuming that you have a Spring Boot application installed in /var/myapp, to install a Spring Boot application as a systemd service create a script named myapp.service using the following example and place it in /etc/systemd/system directory:
[Unit]
Description=myapp
After=syslog.target
[Service]
User=myapp
ExecStart=/var/myapp/myapp.jar
SuccessExitStatus=143
[Install]
WantedBy=multi-user.target| Remember to change the |
Note that unlike when running as an init.d service, user that runs the application, PID file and console log file behave differently under systemd and must be configured using appropriate fields in ‘service’ script. Consult the service unit configuration man page for more details.
To flag the application to start automatically on system boot use the following command:
$ systemctl enable myapp.serviceRefer to man systemctl for more details.
55.1.3 Customizing the startup script
The script accepts the following parameters as environment variables, so you can change the default behavior in a script or on the command line:
| Variable | Description |
|---|---|
|
|
The “mode” of operation. The default depends on the way the jar was built, but will usually be |
|
|
If the |
|
|
The root name of the pid folder ( |
|
|
The name of the folder to put log files in ( |
|
|
The name of the log file in the |
|
|
The name of the app. If the jar is run from a symlink the script guesses the app name, but if it is not a symlink, or you want to explicitly set the app name this can be useful. |
|
|
The arguments to pass to the program (the Spring Boot app). |
|
|
The location of the |
|
|
Options that are passed to the JVM when it is launched. |
|
|
The explicit location of the jar file, in case the script is being used to launch a jar that it is not actually embedded in. |
|
|
if not empty will set the |
| The |
In addition, the following properties can be changed when the script is written by using the embeddedLaunchScriptProperties option of the Spring Boot Maven or Gradle plugins.
| Name | Description |
|---|---|
|
|
The script mode. Defaults to |
|
|
The |
|
|
The |
|
|
The |
|
|
The |
|
|
If the |
55.1.4 Customizing the startup script with a conf file
With the exception of JARFILE and APP_NAME, the above settings can be configured using a .conf file,
JAVA_OPTS=-Xmx1024M
LOG_FOLDER=/custom/log/folderThe file should be situated next to the jar file and have the same name but suffixed with .conf rather than .jar. For example, a jar named /var/myapp/myapp.jar will use the configuration file named /var/myapp/myapp.conf if it exists.
To learn about securing this file appropriately, please refer to the guidelines for securing an init.d service.
56. Microsoft Windows services
Spring Boot application can be started as Windows service using winsw.
A sample maintained separately to the core of Spring Boot describes step-by-step how you can create a Windows service for your Spring Boot application.
57. What to read next
Check out the Cloud Foundry, Heroku, OpenShift and Boxfuse web sites for more information about the kinds of features that a PaaS can offer. These are just four of the most popular Java PaaS providers, since Spring Boot is so amenable to cloud-based deployment you’re free to consider other providers as well.
The next section goes on to cover the Spring Boot CLI; or you can jump ahead to read about build tool plugins.
Part VII. Spring Boot CLI
The Spring Boot CLI is a command line tool that can be used if you want to quickly develop with Spring. It allows you to run Groovy scripts, which means that you have a familiar Java-like syntax, without so much boilerplate code. You can also bootstrap a new project or write your own command for it.
58. Installing the CLI
The Spring Boot CLI can be installed manually; using SDKMAN! (the SDK Manager) or using Homebrew or MacPorts if you are an OSX user. See Section 10.2, “Installing the Spring Boot CLI” in the “Getting started” section for comprehensive installation instructions.
59. Using the CLI
Once you have installed the CLI you can run it by typing spring. If you run spring without any arguments, a simple help screen is displayed:
$ spring
usage: spring [--help] [--version]
[]
Available commands are:
run [options] [--] [args]
Run a spring groovy script
... more command help is shown here You can use help to get more details about any of the supported commands. For example:
$ spring help run
spring run - Run a spring groovy script
usage: spring run [options] [--] [args]
Option Description
------ -----------
--autoconfigure [Boolean] Add autoconfigure compiler
transformations (default: true)
--classpath, -cp Additional classpath entries
-e, --edit Open the file with the default system
editor
--no-guess-dependencies Do not attempt to guess dependencies
--no-guess-imports Do not attempt to guess imports
-q, --quiet Quiet logging
-v, --verbose Verbose logging of dependency
resolution
--watch Watch the specified file for changes The version command provides a quick way to check which version of Spring Boot you are using.
$ spring version
Spring CLI v1.3.7.RELEASE59.1 Running applications using the CLI
You can compile and run Groovy source code using the run command. The Spring Boot CLI is completely self-contained so you don’t need any external Groovy installation.
Here is an example “hello world” web application written in Groovy:
hello.groovy.
@RestController
class WebApplication {
@RequestMapping("/")
String home() {
"Hello World!"
}
}
To compile and run the application type:
$ spring run hello.groovyTo pass command line arguments to the application, you need to use a -- to separate them from the “spring” command arguments, e.g.
$ spring run hello.groovy -- --server.port=9000To set JVM command line arguments you can use the JAVA_OPTS environment variable, e.g.
$ JAVA_OPTS=-Xmx1024m spring run hello.groovy59.1.1 Deduced “grab” dependencies
Standard Groovy includes a @Grab annotation which allows you to declare dependencies on a third-party libraries. This useful technique allows Groovy to download jars in the same way as Maven or Gradle would, but without requiring you to use a build tool.
Spring Boot extends this technique further, and will attempt to deduce which libraries to “grab” based on your code. For example, since the WebApplicationcode above uses @RestController annotations, “Tomcat” and “Spring MVC” will be grabbed.
The following items are used as “grab hints”:
| Items | Grabs |
|---|---|
|
|
JDBC Application. |
|
|
JMS Application. |
|
|
Caching abstraction. |
|
|
JUnit. |
|
|
RabbitMQ. |
|
|
Project Reactor. |
| extends |
Spock test. |
|
|
Spring Batch. |
|
|
Spring Integration. |
|
|
Spring Mobile. |
|
|
Spring MVC + Embedded Tomcat. |
|
|
Spring Security. |
|
|
Spring Transaction Management. |
| See subclasses of |
59.1.2 Deduced “grab” coordinates
Spring Boot extends Groovy’s standard @Grab support by allowing you to specify a dependency without a group or version, for example @Grab('freemarker'). This will consult Spring Boot’s default dependency metadata to deduce the artifact’s group and version. Note that the default metadata is tied to the version of the CLI that you’re using – it will only change when you move to a new version of the CLI, putting you in control of when the versions of your dependencies may change. A table showing the dependencies and their versions that are included in the default metadata can be found in the appendix.
59.1.3 Default import statements
To help reduce the size of your Groovy code, several import statements are automatically included. Notice how the example above refers to @Component,@RestController and @RequestMapping without needing to use fully-qualified names or import statements.
| Many Spring annotations will work without using |
59.1.4 Automatic main method
Unlike the equivalent Java application, you do not need to include a public static void main(String[] args) method with your Groovy scripts. ASpringApplication is automatically created, with your compiled code acting as the source.
59.1.5 Custom dependency management
By default, the CLI uses the dependency management declared in spring-boot-dependencies when resolving @Grab dependencies. Additional dependency management, that will override the default dependency management, can be configured using the @DependencyManagementBom annotation. The annotation’s value should specify the coordinates (groupId:artifactId:version) of one or more Maven BOMs.
For example, the following declaration:
@DependencyManagementBom("com.example.custom-bom:1.0.0")Will pick up custom-bom-1.0.0.pom in a Maven repository under com/example/custom-versions/1.0.0/.
When multiple BOMs are specified they are applied in the order that they’re declared. For example:
@DependencyManagementBom(["com.example.custom-bom:1.0.0",
"com.example.another-bom:1.0.0"])indicates that dependency management in another-bom will override the dependency management in custom-bom.
You can use @DependencyManagementBom anywhere that you can use @Grab, however, to ensure consistent ordering of the dependency management, you can only use @DependencyManagementBom at most once in your application. A useful source of dependency management (that is a superset of Spring Boot’s dependency management) is the Spring IO Platform, e.g. @DependencyManagementBom('io.spring.platform:platform-bom:1.1.2.RELEASE').
59.2 Testing your code
The test command allows you to compile and run tests for your application. Typical usage looks like this:
$ spring test app.groovy tests.groovy
Total: 1, Success: 1, : Failures: 0
Passed? trueIn this example, tests.groovy contains JUnit @Test methods or Spock Specification classes. All the common framework annotations and static methods should be available to you without having to import them.
Here is the tests.groovy file that we used above (with a JUnit test):
class ApplicationTests {
@Test
void homeSaysHello() {
assertEquals("Hello World!", new WebApplication().home())
}
}| If you have more than one test source files, you might prefer to organize them into a |
59.3 Applications with multiple source files
You can use “shell globbing” with all commands that accept file input. This allows you to easily use multiple files from a single directory, e.g.
$ spring run *.groovyThis technique can also be useful if you want to segregate your “test” or “spec” code from the main application code:
$ spring test app/*.groovy test/*.groovy59.4 Packaging your application
You can use the jar command to package your application into a self-contained executable jar file. For example:
$ spring jar my-app.jar *.groovyThe resulting jar will contain the classes produced by compiling the application and all of the application’s dependencies so that it can then be run using java -jar. The jar file will also contain entries from the application’s classpath. You can add explicit paths to the jar using --include and --exclude (both are comma-separated, and both accept prefixes to the values “+” and “-” to signify that they should be removed from the defaults). The default includes are
public/**, resources/**, static/**, templates/**, META-INF/**, *and the default excludes are
.*, repository/**, build/**, target/**, **/*.jar, **/*.groovySee the output of spring help jar for more information.
59.5 Initialize a new project
The init command allows you to create a new project using start.spring.io without leaving the shell. For example:
$ spring init --dependencies=web,data-jpa my-project
Using service at https://start.spring.io
Project extracted to '/Users/developer/example/my-project'This creates a my-project directory with a Maven-based project using spring-boot-starter-web and spring-boot-starter-data-jpa. You can list the capabilities of the service using the --list flag
$ spring init --list
=======================================
Capabilities of https://start.spring.io
=======================================
Available dependencies:
-----------------------
actuator - Actuator: Production ready features to help you monitor and manage your application
...
web - Web: Support for full-stack web development, including Tomcat and spring-webmvc
websocket - Websocket: Support for WebSocket development
ws - WS: Support for Spring Web Services
Available project types:
------------------------
gradle-build - Gradle Config [format:build, build:gradle]
gradle-project - Gradle Project [format:project, build:gradle]
maven-build - Maven POM [format:build, build:maven]
maven-project - Maven Project [format:project, build:maven] (default)
...The init command supports many options, check the help output for more details. For instance, the following command creates a gradle project using Java 8 and war packaging:
$ spring init --build=gradle --java-version=1.8 --dependencies=websocket --packaging=war sample-app.zip
Using service at https://start.spring.io
Content saved to 'sample-app.zip'59.6 Using the embedded shell
Spring Boot includes command-line completion scripts for BASH and zsh shells. If you don’t use either of these shells (perhaps you are a Windows user) then you can use the shell command to launch an integrated shell.
$ spring shell
Spring Boot (v1.3.7.RELEASE)
Hit TAB to complete. Type \'help' and hit RETURN for help, and \'exit' to quit.From inside the embedded shell you can run other commands directly:
$ version
Spring CLI v1.3.7.RELEASEThe embedded shell supports ANSI color output as well as tab completion. If you need to run a native command you can use the ! prefix. Hitting ctrl-cwill exit the embedded shell.
59.7 Adding extensions to the CLI
You can add extensions to the CLI using the install command. The command takes one or more sets of artifact coordinates in the format group:artifact:version. For example:
$ spring install com.example:spring-boot-cli-extension:1.0.0.RELEASEIn addition to installing the artifacts identified by the coordinates you supply, all of the artifacts' dependencies will also be installed.
To uninstall a dependency use the uninstall command. As with the install command, it takes one or more sets of artifact coordinates in the format group:artifact:version. For example:
$ spring uninstall com.example:spring-boot-cli-extension:1.0.0.RELEASEIt will uninstall the artifacts identified by the coordinates you supply and their dependencies.
To uninstall all additional dependencies you can use the --all option. For example:
$ spring uninstall --all60. Developing application with the Groovy beans DSL
Spring Framework 4.0 has native support for a beans{} “DSL” (borrowed from Grails), and you can embed bean definitions in your Groovy application scripts using the same format. This is sometimes a good way to include external features like middleware declarations. For example:
@Configuration
class Application implements CommandLineRunner {
@Autowired
SharedService service
@Override
void run(String... args) {
println service.message
}
}
import my.company.SharedService
beans {
service(SharedService) {
message = "Hello World"
}
}You can mix class declarations with beans{} in the same file as long as they stay at the top level, or you can put the beans DSL in a separate file if you prefer.
61. Configuring the CLI with settings.xml
The Spring Boot CLI uses Aether, Maven’s dependency resolution engine, to resolve dependencies. The CLI makes use of the Maven configuration found in ~/.m2/settings.xml to configure Aether. The following configuration settings are honored by the CLI:
- Offline
- Mirrors
- Servers
- Proxies
-
Profiles
- Activation
- Repositories
- Active profiles
Please refer to Maven’s settings documentation for further information.
62. What to read next
There are some sample groovy scripts available from the GitHub repository that you can use to try out the Spring Boot CLI. There is also extensive javadoc throughout the source code.
If you find that you reach the limit of the CLI tool, you will probably want to look at converting your application to full Gradle or Maven built “groovy project”. The next section covers Spring Boot’s Build tool plugins that you can use with Gradle or Maven.
Part VIII. Build tool plugins
Spring Boot provides build tool plugins for Maven and Gradle. The plugins offer a variety of features, including the packaging of executable jars. This section provides more details on both plugins, as well as some help should you need to extend an unsupported build system. If you are just getting started, you might want to read “Chapter 13, Build systems” from the Part III, “Using Spring Boot” section first.
63. Spring Boot Maven plugin
The Spring Boot Maven Plugin provides Spring Boot support in Maven, allowing you to package executable jar or war archives and run an application “in-place”. To use it you must be using Maven 3.2 (or better).
| Refer to the Spring Boot Maven Plugin Site for complete plugin documentation. |
63.1 Including the plugin
To use the Spring Boot Maven Plugin simply include the appropriate XML in the plugins section of your pom.xml
xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
This configuration will repackage a jar or war that is built during the package phase of the Maven lifecycle. The following example shows both the repackaged jar, as well as the original jar, in the target directory:
$ mvn package
$ ls target/*.jar
target/myproject-1.0.0.jar target/myproject-1.0.0.jar.originalIf you don’t include the
$ mvn package spring-boot:repackage
$ ls target/*.jar
target/myproject-1.0.0.jar target/myproject-1.0.0.jar.originalIf you are using a milestone or snapshot release you will also need to add appropriate pluginRepository elements:
63.2 Packaging executable jar and war files
Once spring-boot-maven-plugin has been included in your pom.xml it will automatically attempt to rewrite archives to make them executable using the spring-boot:repackage goal. You should configure your project to build a jar or war (as appropriate) using the usual packaging element:
xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
Your existing archive will be enhanced by Spring Boot during the package phase. The main class that you want to launch can either be specified using a configuration option, or by adding a Main-Class attribute to the manifest in the usual way. If you don’t specify a main class the plugin will search for a class with a public static void main(String[] args) method.
To build and run a project artifact, you can type the following:
$ mvn package
$ java -jar target/mymodule-0.0.1-SNAPSHOT.jarTo build a war file that is both executable and deployable into an external container you need to mark the embedded container dependencies as “provided”, e.g:
xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
| See the “Section 80.1, “Create a deployable war file”” section for more details on how to create a deployable war file. |
Advanced configuration options and examples are available in the plugin info page.
64. Spring Boot Gradle plugin
The Spring Boot Gradle Plugin provides Spring Boot support in Gradle, allowing you to package executable jar or war archives, run Spring Boot applications and use the dependency management provided by spring-boot-dependencies.
64.1 Including the plugin
To use the Spring Boot Gradle Plugin simply include a buildscript dependency and apply the spring-boot plugin:
buildscript {
dependencies {
classpath("org.springframework.boot:spring-boot-gradle-plugin:1.3.7.RELEASE")
}
}
apply plugin: 'spring-boot'If you are using a milestone or snapshot release you will also need to add appropriate repositories reference:
buildscript {
repositories {
maven.url "http://repo.spring.io/snapshot"
maven.url "http://repo.spring.io/milestone"
}
// ...
}64.2 Gradle dependency management
The spring-boot plugin automatically applies the Dependency Management Plugin and configures in to import the spring-boot-starter-parent bom. This provides a similar dependency management experience to the one that is enjoyed by Maven users. For example, it allows you to omit version numbers when declaring dependencies that are managed in the bom. To make use of this functionality, simply declare dependencies in the usual way, but leave the version number empty:
dependencies {
compile("org.springframework.boot:spring-boot-starter-web")
compile("org.thymeleaf:thymeleaf-spring4")
compile("nz.net.ultraq.thymeleaf:thymeleaf-layout-dialect")
}| The version of the |
The dependency management plugin will only supply a version where one is not specified. To use a version of an artifact that differs from the one that the plugin would provide, simply specify the version when you declare the dependency as you usually would. For example:
dependencies {
compile("org.thymeleaf:thymeleaf-spring4:2.1.1.RELEASE")
}To learn more about the capabilities of the Dependency Management Plugin, please refer to its documentation.
64.3 Packaging executable jar and war files
Once the spring-boot plugin has been applied to your project it will automatically attempt to rewrite archives to make them executable using thebootRepackage task. You should configure your project to build a jar or war (as appropriate) in the usual way.
The main class that you want to launch can either be specified using a configuration option, or by adding a Main-Class attribute to the manifest. If you don’t specify a main class the plugin will search for a class with a public static void main(String[] args) method.
| Check Section 64.6, “Repackage configuration” for a full list of configuration options. |
To build and run a project artifact, you can type the following:
$ gradle build
$ java -jar build/libs/mymodule-0.0.1-SNAPSHOT.jarTo build a war file that is both executable and deployable into an external container, you need to mark the embedded container dependencies as belonging to a configuration named “providedRuntime”, e.g:
...
apply plugin: 'war'
war {
baseName = 'myapp'
version = '0.5.0'
}
repositories {
jcenter()
maven { url "http://repo.spring.io/libs-snapshot" }
}
configurations {
providedRuntime
}
dependencies {
compile("org.springframework.boot:spring-boot-starter-web")
providedRuntime("org.springframework.boot:spring-boot-starter-tomcat")
...
}| See the “Section 80.1, “Create a deployable war file”” section for more details on how to create a deployable war file. |
64.4 Running a project in-place
To run a project in place without building a jar first you can use the “bootRun” task:
$ gradle bootRunIf devtools has been added to your project it will automatically monitor your application for changes. Alternatively, you can also run the application so that your static classpath resources (i.e. in src/main/resources by default) are reloadable in the live application, which can be helpful at development time.
bootRun {
addResources = true
}Making static classpath resources reloadable means that bootRun does not use the output of the processResources task, i.e., when invoked using bootRun, your application will use the resources in their unprocessed form.
64.5 Spring Boot plugin configuration
The gradle plugin automatically extends your build script DSL with a springBoot element for global configuration of the Boot plugin. Set the appropriate properties as you would with any other Gradle extension (see below for a list of configuration options):
springBoot {
backupSource = false
}64.6 Repackage configuration
The plugin adds a bootRepackage task which you can also configure directly, e.g.:
bootRepackage {
mainClass = 'demo.Application'
}The following configuration options are available:
| Name | Description |
|---|---|
|
|
Boolean flag to switch the repackager off (sometimes useful if you want the other Boot features but not this one) |
|
|
The main class that should be run. If not specified, and you have applied the application plugin, the |
|
|
A file name segment (before the extension) to add to the archive, so that the original is preserved in its original location. Defaults to null in which case the archive is repackaged in place. The default is convenient for many purposes, but if you want to use the original jar as a dependency in another project, it’s best to use an extension to define the executable archive. |
|
|
The name or value of the |
|
|
The name of the custom configuration which is used to populate the nested lib directory (without specifying this you get all compile and runtime dependencies). |
|
|
Boolean flag to indicate if jar files are fully executable on Unix like operating systems. Defaults to |
|
|
The embedded launch script to prepend to the front of the jar if it is fully executable. If not specified the 'Spring Boot' default script will be used. |
|
|
Additional properties that to be expanded in the launch script. The default script supports a |
|
|
Boolean flag to indicate if the devtools jar should be excluded from the repackaged archives. Defaults to |
64.7 Repackage with custom Gradle configuration
Sometimes it may be more appropriate to not package default dependencies resolved from compile, runtime and provided scopes. If the created executable jar file is intended to be run as it is, you need to have all dependencies nested inside it; however, if the plan is to explode a jar file and run the main class manually, you may already have some of the libraries available via CLASSPATH. This is a situation where you can repackage your jar with a different set of dependencies.
Using a custom configuration will automatically disable dependency resolving from compile, runtime and provided scopes. Custom configuration can be either defined globally (inside the springBoot section) or per task.
task clientJar(type: Jar) {
appendix = 'client'
from sourceSets.main.output
exclude('**/*Something*')
}
task clientBoot(type: BootRepackage, dependsOn: clientJar) {
withJarTask = clientJar
customConfiguration = "mycustomconfiguration"
}In above example, we created a new clientJar Jar task to package a customized file set from your compiled sources. Then we created a new clientBootBootRepackage task and instructed it to work with only clientJar task and mycustomconfiguration.
configurations {
mycustomconfiguration.exclude group: 'log4j'
}
dependencies {
mycustomconfiguration configurations.runtime
}The configuration that we are referring to in BootRepackage is a normal Gradle configuration. In the above example we created a new configuration namedmycustomconfiguration instructing it to derive from a runtime and exclude the log4j group. If the clientBoot task is executed, the repackaged boot jar will have all dependencies from runtime but no log4j jars.
64.7.1 Configuration options
The following configuration options are available:
| Name | Description |
|---|---|
|
|
The main class that should be run by the executable archive. |
|
|
The name of the provided configuration (defaults to |
|
|
If the original source archive should be backed-up before being repackaged (defaults to |
|
|
The name of the custom configuration. |
|
|
The type of archive, corresponding to how the dependencies are laid out inside (defaults to a guess based on the archive type). See available layouts for more details. |
|
|
A list of dependencies (in the form “groupId:artifactId” that must be unpacked from fat jars in order to run. Items are still packaged into the fat jar, but they will be automatically unpacked when it runs. |
64.7.2 Available layouts
The layout attribute configures the format of the archive and whether the bootstrap loader should be included or not. The following layouts are available:
| Name | Description | Executable |
|---|---|---|
|
|
Regular executable JAR layout. |
Yes |
|
|
Executable WAR layout. |
Yes |
|
|
Similar to |
Yes |
|
|
Bundle dependencies (excluding those with |
No |
|
|
Bundle all dependencies and project resources. |
No |
64.8 Understanding how the Gradle plugin works
When spring-boot is applied to your Gradle project a default task named bootRepackage is created automatically. The bootRepackage task depends on Gradle assemble task, and when executed, it tries to find all jar artifacts whose qualifier is empty (i.e. tests and sources jars are automatically skipped).
Due to the fact that bootRepackage finds 'all' created jar artifacts, the order of Gradle task execution is important. Most projects only create a single jar file, so usually this is not an issue; however, if you are planning to create a more complex project setup, with custom Jar and BootRepackage tasks, there are few tweaks to consider.
If you are 'just' creating custom jar files from your project you can simply disable default jar and bootRepackage tasks:
jar.enabled = false
bootRepackage.enabled = falseAnother option is to instruct the default bootRepackage task to only work with a default jar task.
bootRepackage.withJarTask = jarIf you have a default project setup where the main jar file is created and repackaged, 'and' you still want to create additional custom jars, you can combine your custom repackage tasks together and use dependsOn so that the bootJars task will run after the default bootRepackage task is executed:
task bootJars
bootJars.dependsOn = [clientBoot1,clientBoot2,clientBoot3]
build.dependsOn(bootJars)All the above tweaks are usually used to avoid situations where an already created boot jar is repackaged again. Repackaging an existing boot jar will not break anything, but you may find that it includes unnecessary dependencies.
64.9 Publishing artifacts to a Maven repository using Gradle
If you are declaring dependencies without versions and you want to publish artifacts to a Maven repository you will need to configure the Maven publication with details of Spring Boot’s dependency management. This can be achieved by configuring it to publish poms that inherit from spring-boot-starter-parent or that import dependency management from spring-boot-dependencies. The exact details of this configuration depend on how you’re using Gradle and how you’re trying to publish the artifacts.
64.9.1 Configuring Gradle to produce a pom that inherits dependency management
The following is an example of configuring Gradle to generate a pom that inherits from spring-boot-starter-parent. Please refer to the Gradle User Guidefor further information.
uploadArchives {
repositories {
mavenDeployer {
pom {
project {
parent {
groupId "org.springframework.boot"
artifactId "spring-boot-starter-parent"
version "1.3.7.RELEASE"
}
}
}
}
}
}64.9.2 Configuring Gradle to produce a pom that imports dependency management
The following is an example of configuring Gradle to generate a pom that imports the dependency management provided by spring-boot-dependencies. Please refer to the Gradle User Guide for further information.
uploadArchives {
repositories {
mavenDeployer {
pom {
project {
dependencyManagement {
dependencies {
dependency {
groupId "org.springframework.boot"
artifactId "spring-boot-dependencies"
version "1.3.7.RELEASE"
type "pom"
scope "import"
}
}
}
}
}
}
}
}65. Spring Boot AntLib module
The Spring Boot AntLib module provides basic Spring Boot support for Apache Ant. You can use the module to create executable jars. To use the module you need to declare an additional spring-boot namespace in your build.xml:
xmlns:ivy="antlib:org.apache.ivy.ant"
xmlns:spring-boot="antlib:org.springframework.boot.ant"
name="myapp" default="build">
...
You’ll need to remember to start Ant using the -lib option, for example:
$ ant -lib | The “Using Spring Boot” section includes a more complete example of using Apache Ant with |
65.1 Spring Boot Ant tasks
Once the spring-boot-antlib namespace has been declared, the following additional tasks are available.
65.1.1 spring-boot:exejar
The exejar task can be used to creates a Spring Boot executable jar. The following attributes are supported by the task:
| Attribute | Description | Required |
|---|---|---|
|
|
The destination jar file to create |
Yes |
|
|
The root directory of Java class files |
Yes |
|
|
The main application class to run |
No (default is first class found declaring a |
The following nested elements can be used with the task:
| Element | Description |
|---|---|
|
|
One or more Resource Collections describing a set of Resources that should be added to the content of the created jar file. |
|
|
One or more Resource Collections that should be added to the set of jar libraries that make up the runtime dependency classpath of the application. |
65.1.2 Examples
Specify start-class.
destfile="target/my-application.jar"
classes="target/classes" start-class="com.foo.MyApplication">
dir="src/main/resources" />
dir="lib" />
Detect start-class.
destfile="target/my-application.jar" classes="target/classes">
dir="lib" />
65.2 spring-boot:findmainclass
The findmainclass task is used internally by exejar to locate a class declaring a main. You can also use this task directly in your build if needed. The following attributes are supported
| Attribute | Description | Required |
|---|---|---|
|
|
The root directory of Java class files |
Yes (unless |
|
|
Can be used to short-circuit the |
No |
|
|
The Ant property that should be set with the result |
No (result will be logged if unspecified) |
65.2.1 Examples
Find and log.
classesroot="target/classes" />
Find and set.
classesroot="target/classes" property="main-class" />
Override and set.
mainclass="com.foo.MainClass" property="main-class" />
66. Supporting other build systems
If you want to use a build tool other than Maven, Gradle or Ant, you will likely need to develop your own plugin. Executable jars need to follow a specific format and certain entries need to be written in an uncompressed form (see the executable jar format section in the appendix for details).
The Spring Boot Maven and Gradle plugins both make use of spring-boot-loader-tools to actually generate jars. You are also free to use this library directly yourself if you need to.
66.1 Repackaging archives
To repackage an existing archive so that it becomes a self-contained executable archive use org.springframework.boot.loader.tools.Repackager. The Repackager class takes a single constructor argument that refers to an existing jar or war archive. Use one of the two available repackage() methods to either replace the original file or write to a new destination. Various settings can also be configured on the repackager before it is run.
66.2 Nested libraries
When repackaging an archive you can include references to dependency files using the org.springframework.boot.loader.tools.Libraries interface. We don’t provide any concrete implementations of Libraries here as they are usually build system specific.
If your archive already includes libraries you can use Libraries.NONE.
66.3 Finding a main class
If you don’t use Repackager.setMainClass() to specify a main class, the repackager will use ASM to read class files and attempt to find a suitable class with a public static void main(String[] args) method. An exception is thrown if more than one candidate is found.
66.4 Example repackage implementation
Here is a typical example repackage:
Repackager repackager = new Repackager(sourceJarFile);
repackager.setBackupSource(false);
repackager.repackage(new Libraries() {
@Override
public void doWithLibraries(LibraryCallback callback) throws IOException {
// Build system specific implementation, callback for each dependency
// callback.library(new Library(nestedFile, LibraryScope.COMPILE));
}
});67. What to read next
If you’re interested in how the build tool plugins work you can look at the spring-boot-tools module on GitHub. More technical details of the executable jar format are covered in the appendix.
If you have specific build-related questions you can check out the “how-to” guides.
Part IX. ‘How-to’ guides
This section provides answers to some common ‘how do I do that…’ type of questions that often arise when using Spring Boot. This is by no means an exhaustive list, but it does cover quite a lot.
If you are having a specific problem that we don’t cover here, you might want to check out stackoverflow.com to see if someone has already provided an answer; this is also a great place to ask new questions (please use the spring-boot tag).
We’re also more than happy to extend this section; If you want to add a ‘how-to’ you can send us a pull request.
68. Spring Boot application
68.1 Troubleshoot auto-configuration
The Spring Boot auto-configuration tries its best to ‘do the right thing’, but sometimes things fail and it can be hard to tell why.
There is a really useful ConditionEvaluationReport available in any Spring Boot ApplicationContext. You will see it if you enable DEBUG logging output. If you use the spring-boot-actuator there is also an autoconfig endpoint that renders the report in JSON. Use that to debug the application and see what features have been added (and which not) by Spring Boot at runtime.
Many more questions can be answered by looking at the source code and the javadoc. Some rules of thumb:
- Look for classes called
*AutoConfigurationand read their sources, in particular the@Conditional*annotations to find out what features they enable and when. Add--debugto the command line or a System property-Ddebugto get a log on the console of all the auto-configuration decisions that were made in your app. In a running Actuator app look at theautoconfigendpoint (‘/autoconfig’ or the JMX equivalent) for the same information. - Look for classes that are
@ConfigurationProperties(e.g.ServerProperties) and read from there the available external configuration options. The@ConfigurationPropertieshas anameattribute which acts as a prefix to external properties, thusServerPropertieshasprefix="server"and its configuration properties areserver.port,server.addressetc. In a running Actuator app look at theconfigpropsendpoint. - Look for use of
RelaxedPropertyResolverto pull configuration values explicitly out of theEnvironment. It often is used with a prefix. - Look for
@Valueannotations that bind directly to theEnvironment. This is less flexible than theRelaxedPropertyResolverapproach, but does allow some relaxed binding, specifically for OS environment variables (soCAPITALS_AND_UNDERSCORESare synonyms forperiod.separated). - Look for
@ConditionalOnExpressionannotations that switch features on and off in response to SpEL expressions, normally evaluated with placeholders resolved from theEnvironment.
68.2 Customize the Environment or ApplicationContext before it starts
A SpringApplication has ApplicationListeners and ApplicationContextInitializers that are used to apply customizations to the context or environment. Spring Boot loads a number of such customizations for use internally from META-INF/spring.factories. There is more than one way to register additional ones:
- Programmatically per application by calling the
addListenersandaddInitializersmethods onSpringApplicationbefore you run it. - Declaratively per application by setting
context.initializer.classesorcontext.listener.classes. - Declaratively for all applications by adding a
META-INF/spring.factoriesand packaging a jar file that the applications all use as a library.
The SpringApplication sends some special ApplicationEvents to the listeners (even some before the context is created), and then registers the listeners for events published by the ApplicationContext as well. See Section 23.4, “Application events and listeners” in the ‘Spring Boot features’ section for a complete list.
68.3 Build an ApplicationContext hierarchy (adding a parent or root context)
You can use the ApplicationBuilder class to create parent/child ApplicationContext hierarchies. See Section 23.3, “Fluent builder API” in the ‘Spring Boot features’ section for more information.
68.4 Create a non-web application
Not all Spring applications have to be web applications (or web services). If you want to execute some code in a main method, but also bootstrap a Spring application to set up the infrastructure to use, then it’s easy with the SpringApplication features of Spring Boot. A SpringApplication changes its ApplicationContext class depending on whether it thinks it needs a web application or not. The first thing you can do to help it is to just leave the servlet API dependencies off the classpath. If you can’t do that (e.g. you are running 2 applications from the same code base) then you can explicitly callsetWebEnvironment(false) on your SpringApplication instance, or set the applicationContextClass property (through the Java API or with external properties). Application code that you want to run as your business logic can be implemented as a CommandLineRunner and dropped into the context as a @Bean definition.
69. Properties & configuration
69.1 Externalize the configuration of SpringApplication
A SpringApplication has bean properties (mainly setters) so you can use its Java API as you create the application to modify its behavior. Or you can externalize the configuration using properties in spring.main.*. E.g. in application.properties you might have.
spring.main.web_environment=false
spring.main.banner_mode=offand then the Spring Boot banner will not be printed on startup, and the application will not be a web application.
| The example above also demonstrates how flexible binding allows the use of underscores ( |
Properties defined in external configuration overrides the values specified via the Java API with the notable exception of the sources used to create the ApplicationContext. Let’s consider this application
new SpringApplicationBuilder()
.bannerMode(Banner.Mode.OFF)
.sources(demo.MyApp.class)
.run(args);used with the following configuration:
spring.main.sources=com.acme.Config,com.acme.ExtraConfig
spring.main.banner_mode=consoleThe actual application will now show the banner (as overridden by configuration) and use three sources for the ApplicationContext (in that order): demo.MyApp, com.acme.Config, com.acme.ExtraConfig.
69.2 Change the location of external properties of an application
By default properties from different sources are added to the Spring Environment in a defined order (see Chapter 24, Externalized Configuration in the ‘Spring Boot features’ section for the exact order).
A nice way to augment and modify this is to add @PropertySource annotations to your application sources. Classes passed to the SpringApplicationstatic convenience methods, and those added using setSources() are inspected to see if they have @PropertySources, and if they do, those properties are added to the Environment early enough to be used in all phases of the ApplicationContext lifecycle. Properties added in this way have lower priority than any added using the default locations (e.g. application.properties), system properties, environment variables or the command line.
You can also provide System properties (or environment variables) to change the behavior:
spring.config.name(SPRING_CONFIG_NAME), defaults toapplicationas the root of the file name.spring.config.location(SPRING_CONFIG_LOCATION) is the file to load (e.g. a classpath resource or a URL). A separateEnvironmentproperty source is set up for this document and it can be overridden by system properties, environment variables or the command line.
No matter what you set in the environment, Spring Boot will always load application.properties as described above. If YAML is used then files with the ‘.yml’ extension are also added to the list by default.
Spring Boot logs the configuration files that are loaded at DEBUG level and the candidates it has not found at TRACE level.
See ConfigFileApplicationListener for more detail.
69.3 Use ‘short’ command line arguments
Some people like to use (for example) --port=9000 instead of --server.port=9000 to set configuration properties on the command line. You can easily enable this by using placeholders in application.properties, e.g.
server.port=${port:8080}| If you are inheriting from the |
| In this specific case the port binding will work in a PaaS environment like Heroku and Cloud Foundry, since in those two platforms the |
69.4 Use YAML for external properties
YAML is a superset of JSON and as such is a very convenient syntax for storing external properties in a hierarchical format. E.g.
spring:
application:
name: cruncher
datasource:
driverClassName: com.mysql.jdbc.Driver
url: jdbc:mysql://localhost/test
server:
port: 9000Create a file called application.yml and stick it in the root of your classpath, and also add snakeyaml to your dependencies (Maven coordinates org.yaml:snakeyaml, already included if you use the spring-boot-starter). A YAML file is parsed to a Java Map (like a JSON object), and Spring Boot flattens the map so that it is 1-level deep and has period-separated keys, a lot like people are used to with Properties files in Java.
The example YAML above corresponds to an application.properties file
spring.application.name=cruncher
spring.datasource.driverClassName=com.mysql.jdbc.Driver
spring.datasource.url=jdbc:mysql://localhost/test
server.port=9000See Section 24.6, “Using YAML instead of Properties” in the ‘Spring Boot features’ section for more information about YAML.
69.5 Set the active Spring profiles
The Spring Environment has an API for this, but normally you would set a System property (spring.profiles.active) or an OS environment variable (SPRING_PROFILES_ACTIVE). E.g. launch your application with a -D argument (remember to put it before the main class or jar archive):
$ java -jar -Dspring.profiles.active=production demo-0.0.1-SNAPSHOT.jarIn Spring Boot you can also set the active profile in application.properties, e.g.
spring.profiles.active=productionA value set this way is replaced by the System property or environment variable setting, but not by the SpringApplicationBuilder.profiles() method. Thus the latter Java API can be used to augment the profiles without changing the defaults.
See Chapter 25, Profiles in the ‘Spring Boot features’ section for more information.
69.6 Change configuration depending on the environment
A YAML file is actually a sequence of documents separated by --- lines, and each document is parsed separately to a flattened map.
If a YAML document contains a spring.profiles key, then the profiles value (comma-separated list of profiles) is fed into the SpringEnvironment.acceptsProfiles() and if any of those profiles is active that document is included in the final merge (otherwise not).
Example:
server:
port: 9000
---
spring:
profiles: development
server:
port: 9001
---
spring:
profiles: production
server:
port: 0In this example the default port is 9000, but if the Spring profile ‘development’ is active then the port is 9001, and if ‘production’ is active then it is 0.
The YAML documents are merged in the order they are encountered (so later values override earlier ones).
To do the same thing with properties files you can use application-${profile}.properties to specify profile-specific values.
69.7 Discover built-in options for external properties
Spring Boot binds external properties from application.properties (or .yml) (and other places) into an application at runtime. There is not (and technically cannot be) an exhaustive list of all supported properties in a single location because contributions can come from additional jar files on your classpath.
A running application with the Actuator features has a configprops endpoint that shows all the bound and bindable properties available through @ConfigurationProperties.
The appendix includes an application.properties example with a list of the most common properties supported by Spring Boot. The definitive list comes from searching the source code for @ConfigurationProperties and @Value annotations, as well as the occasional use of RelaxedPropertyResolver.
70. Embedded servlet containers
70.1 Add a Servlet, Filter or Listener to an application
There are two ways to add Servlet, Filter, ServletContextListener and the other listeners supported by the Servlet spec to your application. You can either provide Spring beans for them, or enable scanning for Servlet components.
70.1.1 Add a Servlet, Filter or Listener using a Spring bean
To add a Servlet, Filter, or Servlet *Listener provide a @Bean definition for it. This can be very useful when you want to inject configuration or dependencies. However, you must be very careful that they don’t cause eager initialization of too many other beans because they have to be installed in the container very early in the application lifecycle (e.g. it’s not a good idea to have them depend on your DataSource or JPA configuration). You can work around restrictions like that by initializing them lazily when first used instead of on initialization.
In the case of Filters and Servlets you can also add mappings and init parameters by adding a FilterRegistrationBean or ServletRegistrationBean instead of or as well as the underlying component.
| If no If you are migrating a filter that has no |
Disable registration of a Servlet or Filter
As described above any Servlet or Filter beans will be registered with the servlet container automatically. To disable registration of a particular Filter or Servlet bean create a registration bean for it and mark it as disabled. For example:
@Bean
public FilterRegistrationBean registration(MyFilter filter) {
FilterRegistrationBean registration = new FilterRegistrationBean(filter);
registration.setEnabled(false);
return registration;
}70.1.2 Add Servlets, Filters, and Listeners using classpath scanning
@WebServlet, @WebFilter, and @WebListener annotated classes can be automatically registered with an embedded servlet container by annotating a @Configuration class with @ServletComponentScan and specifying the package(s) containing the components that you want to register. By default, @ServletComponentScan will scan from the package of the annotated class.
70.2 Change the HTTP port
In a standalone application the main HTTP port defaults to 8080, but can be set with server.port (e.g. in application.properties or as a System property). Thanks to relaxed binding of Environment values you can also use SERVER_PORT (e.g. as an OS environment variable).
To switch off the HTTP endpoints completely, but still create a WebApplicationContext, use server.port=-1 (this is sometimes useful for testing).
For more details look at Section 27.3.4, “Customizing embedded servlet containers” in the ‘Spring Boot features’ section, or the ServerProperties source code.
70.3 Use a random unassigned HTTP port
To scan for a free port (using OS natives to prevent clashes) use server.port=0.
70.4 Discover the HTTP port at runtime
You can access the port the server is running on from log output or from the EmbeddedWebApplicationContext via its EmbeddedServletContainer. The best way to get that and be sure that it has initialized is to add a @Bean of type ApplicationListenerand pull the container out of the event when it is published.
A useful practice for use with @WebIntegrationTest is to set server.port=0 and then inject the actual (‘local’) port as a @Value. For example:
@RunWith(SpringJUnit4ClassRunner.class)
@SpringApplicationConfiguration(SampleDataJpaApplication.class)
@WebIntegrationTest("server.port:0")
public class CityRepositoryIntegrationTests {
@Autowired
EmbeddedWebApplicationContext server;
@Value("${local.server.port}")
int port;
// ...
}| Don’t try to inject the port with |
70.5 Configure SSL
SSL can be configured declaratively by setting the various server.ssl.* properties, typically in application.properties or application.yml. For example:
server.port=8443
server.ssl.key-store=classpath:keystore.jks
server.ssl.key-store-password=secret
server.ssl.key-password=another-secretSee Ssl for details of all of the supported properties.
Using configuration like the example above means the application will no longer support plain HTTP connector at port 8080. Spring Boot doesn’t support the configuration of both an HTTP connector and an HTTPS connector via application.properties. If you want to have both then you’ll need to configure one of them programmatically. It’s recommended to use application.properties to configure HTTPS as the HTTP connector is the easier of the two to configure programmatically. See the spring-boot-sample-tomcat-multi-connectors sample project for an example.
70.6 Configure Access Logging
Access logs can be configured for Tomcat and Undertow via their respective namespaces.
For instance, the following logs access on Tomcat with a custom pattern.
server.tomcat.basedir=my-tomcat
server.tomcat.accesslog.enabled=true
server.tomcat.accesslog.pattern=%t %a "%r" %s (%D ms)| The default location for logs is a |
Access logging for undertow can be configured in a similar fashion
server.undertow.accesslog.enabled=true
server.undertow.accesslog.pattern=%t %a "%r" %s (%D ms)Logs are stored in a logs directory relative to the working directory of the application. This can be customized via server.undertow.accesslog.directory.
70.7 Use behind a front-end proxy server
Your application might need to send 302 redirects or render content with absolute links back to itself. When running behind a proxy, the caller wants a link to the proxy, and not to the physical address of the machine hosting your app. Typically such situations are handled via a contract with the proxy, which will add headers to tell the back end how to construct links to itself.
If the proxy adds conventional X-Forwarded-For and X-Forwarded-Proto headers (most do this out of the box) the absolute links should be rendered correctly as long as server.use-forward-headers is set to true in your application.properties.
| If your application is running in Cloud Foundry or Heroku the |
70.7.1 Customize Tomcat’s proxy configuration
If you are using Tomcat you can additionally configure the names of the headers used to carry “forwarded” information:
server.tomcat.remote-ip-header=x-your-remote-ip-header
server.tomcat.protocol-header=x-your-protocol-headerTomcat is also configured with a default regular expression that matches internal proxies that are to be trusted. By default, IP addresses in 10/8, 192.168/16, 169.254/16 and 127/8 are trusted. You can customize the valve’s configuration by adding an entry to application.properties, e.g.
server.tomcat.internal-proxies=192\\.168\\.\\d{1,3}\\.\\d{1,3}| The double backslashes are only required when you’re using a properties file for configuration. If you are using YAML, single backslashes are sufficient and a value that’s equivalent to the one shown above would be |