Spring Boot 自定义自动配置（自定义starter pom）

Spring Boot 自定义自动配置（自定义starter pom）

一、自定义starter

1. 新建Spring Boot项目，修改pom.xml文件

<project 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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0modelVersion>
    <parent>
        <groupId>org.springframework.bootgroupId>
        <artifactId>spring-boot-starter-parentartifactId>
        <version>2.1.7.RELEASEversion>
        <relativePath/> 
    parent>
    <groupId>com.xpfgroupId>
    <artifactId>demoautoconfigureartifactId>
    <version>0.0.1-SNAPSHOTversion>
    <name>demoautoconfigurename>
    <description>Demo project for Spring Bootdescription>

    <properties>
        <java.version>1.8java.version>
    properties>

    <dependencies>
        
        
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-autoconfigureartifactId>
            <version>2.1.3.RELEASEversion>
        dependency>
    dependencies>
project>

2. 属性配置

package com.xpf.demoautoconfigure;

import org.springframework.boot.context.properties.ConfigurationProperties;

/**
 * @Title:UserServiceProperties
 * @Package:com.xpf.demoautoconfigure
 * @Author: xiapf
 * @Date:2019/8/28
 * @Descrption: 属性配置
 */
@ConfigurationProperties(prefix = "user.name")
public class UserServiceProperties {

    private static final String NAME = "xpf";

    private String name = NAME;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

• @ConfigurationProperties(prefix = “user.name”),在application.properties中通过user.name = 来设置，若不设置，默认为user.name=xpf。

3. 判断依据类（根据此类的存在与否来创建这个类的Bean）

package com.xpf.demoautoconfigure;

/**
 * @Title:UserService
 * @Package:com.xpf.demoautoconfigure
 * @Author: xiapf
 * @Date:2019/8/28
 * @Descrption: 判断依据类（根据此类的存在与否来创建这个类的Bean）
 */
public class UserService {

    private String name;

    public String getUserName() {
        return "用户姓名：" + name;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

4. 自动配置类

package com.xpf.demoautoconfigure;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

/**
 * @Title:UserServiceAutoConfiguration
 * @Package:com.xpf.demoautoconfigure
 * @Author: xiapf
 * @Date:2019/8/28
 * @Descrption: 自动配置类
 */
@Configuration
@EnableConfigurationProperties(UserServiceProperties.class)
@ConditionalOnClass(UserService.class)
@ConditionalOnProperty(prefix = "user.name", value = "enabled", matchIfMissing = true)
public class UserServiceAutoConfiguration {

    @Autowired
    private UserServiceProperties userServiceProperties;

    @Bean
    @ConditionalOnMissingBean(UserService.class)
    public UserService userService() {
        UserService userService = new UserService();
        userService.setName(userServiceProperties.getName());
        return userService;
    }
}

• @EnableConfigurationProperties(UserServiceProperties.class) ：开启属性注入，通过@EnableConfigurationProperties声明， 使用 @Autowired注入

• @ConditionalOnClass(UserService.class) ：当UserService在类路径的条件下

• @ConditionalOnProperty(prefix = “user.name”,value = “enabled”,matchIfMissing = true)：
  当设置user.name=enabled的情况下，如果没有设置则默认为true，即条件符合

• @Bean ：像使用java配置的方式配置UserService这个Bean

• @ConditionalOnMissingBean(UserService.class)： 当容器中没有这个Bean的时候新建Bean

5. 注册配置

若想自动配置生效，需要注册自动配置类，在src/main/resources下新建META-INF/spring.factories

spring.factories内容如下

org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
com.xpf.demoautoconfigure.UserServiceAutoConfiguration

二、 测试

1. 使用starter

新建Spring Boot项目，将自定义starter作为依赖，修改pom.xml

<project 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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0modelVersion>
    <parent>
        <groupId>org.springframework.bootgroupId>
        <artifactId>spring-boot-starter-parentartifactId>
        <version>2.1.7.RELEASEversion>
        <relativePath/> 
    parent>
    <groupId>com.xpfgroupId>
    <artifactId>testdemoartifactId>
    <version>0.0.1-SNAPSHOTversion>
    <name>testdemoname>
    <description>Demo project for Spring Bootdescription>

    <properties>
        <java.version>1.8java.version>
    properties>

    <dependencies>
        
        <dependency>
            <groupId>com.xpfgroupId>
            <artifactId>demoautoconfigureartifactId>
            <version>0.0.1-SNAPSHOTversion>
        dependency>

        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-webartifactId>
        dependency>

    dependencies>

project>

2. 运行类代码

package com.xpf.testdemo;

import com.xpf.demoautoconfigure.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@SpringBootApplication
@RestController
public class TestdemoApplication {

    @Autowired
    private UserService userService;

    @RequestMapping("/")
    public String index(){
        return userService.getUserName();
    }

    public static void main(String[] args) {
        SpringApplication.run(TestdemoApplication.class, args);
    }

}

3. 运行效果

启动项目，打开浏览器，输入http://localhost:8080/，效果：

三、 Spring Boot自动配置原理

Spring Boot自动配置原理