springboot中mybatis逆向工程与分页的应用

最近在项目中应用到springboot与mybatis，在进行整合过程中遇到一些坑，在此将其整理出来，便于以后查阅与复习。
项目运行环境为：eclispe+jdk1.8+maven

搭建Spring Boot环境

首先建立maven project,在生成的pom文件中加入依赖，代码如下：

    org.springframework.boot
    spring-boot-starter-parent
    1.5.2.RELEASE
     



    UTF-8
    UTF-8
    1.8



    
        org.springframework.boot
        spring-boot-starter-web
    

    
        org.springframework.boot
        spring-boot-starter-test
    

    
        org.mybatis.spring.boot
        mybatis-spring-boot-starter
        1.3.0
    

    
        mysql
        mysql-connector-java
        runtime
    

    
    
          com.github.pagehelper
          pagehelper-spring-boot-starter
          1.2.1
    

    
    
        com.alibaba
        druid
        1.0.29
    



    
        
            org.springframework.boot
            spring-boot-maven-plugin
        
        
        
            org.mybatis.generator
            mybatis-generator-maven-plugin
            1.3.2
            
                ${basedir}/src/main/resources/generator/generatorConfig.xml
                true
                true
            
        
    

配置好依赖后进行maven install,此时注意的坑：
坑一：启动maven install报错：

[ERROR] Failed to execute goal org.springframework.boot:spring-boot-maven-plugin:1.5.2.RELEASE:repackage (default) on project springboot-mybatis: Execution default of goal org.springframework.boot:spring-boot-maven-plugin:1.5.2.RELEASE:repackage failed: Unable to find main class -> [Help 1]
[ERROR] 
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR] 
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/PluginExecutionException

报错原因是没有启动类
解决方法:编写启动类Main.java正常运行！

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

坑二：启动maven install报错：

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.1:compile (default-compile) on project springboot-mybatis: Compilation failure
[ERROR] No compiler is provided in this environment. Perhaps you are running on a JRE rather than a JDK?
[ERROR] -> [Help 1]
[ERROR] 
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR] 
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoFailureException

报错原因：项目的java环境与电脑环境不符合，例如我的新建项目运行环境为J2SE-1.5,报错是在我将其改为jre1.8之后
解决方案：
右键项目——build path——Configure build path——Libraries——双击Jre System Libraries如下图所示：

选择Alternate JRE 如2处的下拉框只有jre，点击3处的Install JREs，依次经过add——Standard VM——next——Directory,选择本机的jdk位置点击finish
在install JREs位置将默认勾选更改jdk,如下图所示，并保存。

再次maven install项目正常。如下所示：

[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 3.351 s
[INFO] Finished at: 2018-09-05T21:20:48+08:00
[INFO] Final Memory: 23M/181M
[INFO] ------------------------------------------------------------------------

在src/main/resources新建文件：application.yml，内容如下所示：

server:
  port: 8080

spring:
    datasource:
        name: test
        url: jdbc:mysql://localhost:3306/test
        username: root
        password: 123456
        driver-class-name: com.mysql.jdbc.Driver

## 该配置节点为独立的节点
mybatis:
  mapper-locations: classpath:mapper/*.xml

#pagehelper分页插件
pagehelper:
    helperDialect: mysql
    reasonable: true
    supportMethodsArguments: true
    params: count=countSql

至此springboot环境搭建完毕！

逆向工程应用

首先应该注意到在pom文件中有配置逆向工程xml文件的位置：src/main/resources/generator/generatorConfig.xml
因而在src/main/resources下新建generator文件夹，并建立generatorConfig.xml文件，代码如下：

根据个人环境将配置文件中的配置进行更改，如数据库密码，包名，对应数据库表
所用的数据库表如下：

DROP TABLE IF EXISTS `user`;
CREATE TABLE `user` (
  `id` bigint(20) NOT NULL,
  `name` varchar(255) NOT NULL,
  `age` int(4) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

INSERT INTO `user` VALUES ('1', 'wanger', '22');
INSERT INTO `user` VALUES ('2', 'zhangsan', '18');
INSERT INTO `user` VALUES ('3', 'lisi', '23');
INSERT INTO `user` VALUES ('4', 'wangwu', '21');

配置完成后，右键项目，选择run as——Maven build——在下面两处分别填入：
Goals: mybatis-generator:generate -e
Profiles: generatorConfig.xml
如下图所示：

出现如下所示，代码生成成功，刷新项目即可。

[INFO] Generating Example class for table user
[INFO] Generating Record class for table user
[INFO] Generating Mapper Interface for table user
[INFO] Generating SQL Map for table user
[INFO] Saving file UserMapper.xml
[INFO] Saving file UserExample.java
[INFO] Saving file User.java
[INFO] Saving file UserMapper.java
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------

需要注意的是：逆向工程生成的代码不会覆盖，因而不能重复多次生成。
此处也有个小坑，逆向工程的代码生成后，启动项目会报如下错误：

***************************
APPLICATION FAILED TO START
***************************

Description:

Field userMapper in com.luis.service.impl.UserServiceImpl required a bean of type 'com.luis.mapper.UserMapper' that could not be found.


Action:

Consider defining a bean of type 'com.luis.mapper.UserMapper' in your configuration.

解决方案：
1、给生成的mapper接口文件前加注解：@Mapper 即可解决。但需要给每一个mapper文件前加，繁琐，因而有第二种类解决办法
2、在启动类前加@MapperScan({“com.luis.mapper”})，其中com.luis.mapper为mapper文件的所在位置。
参考自：http://412887952-qq-com.iteye.com/blog/2392672

分页应用

逆向工程已经生成了entity类，及dao层的mapper接口与*mapper.xml文件，因而/只用编写service层与web层。
首先在UserService中编写接口，代码如下：

public interface UserService {
    User selectByName(String name);
    List findAllUser(int pageNum, int pageSize);
}

在UserServiceImpl文件进行实现，代码如下所示：

@Service
public class UserServiceImpl implements UserService {

    @Autowired
    private UserMapper userMapper;

    @Override
    public User selectByName(String name) {
        UserExample example = new UserExample();
        Criteria criteria = example.createCriteria();
        criteria.andNameEqualTo(name);
        List users = userMapper.selectByExample(example);
        if (users != null && users.size() > 0) {
            return users.get(0);
        }
        return null;
    }

    /**
     * pageNum 开始页数
     * pageSize 每页显示的数据条数
     */
    @Override
    public List findAllUser(int pageNum, int pageSize) {
        //将参数传给方法实现分页
        PageHelper.startPage(pageNum, pageSize);
        UserExample example = new UserExample();
        List list = userMapper.selectByExample(example);
        return list;
    }
}

最后在controller层对查询结果进行接收，UserController代码如下：

@Controller
@RestController
public class UserController {

    @Autowired
    private UserService userService;

    @RequestMapping("/test")
    public User querUserByName() {
        User user = userService.selectByName("luis");
        System.out.println(user.toString());
        return user;
    }

    @RequestMapping("/list")
    public List querUser() {
        List list = userService.findAllUser(1, 2);
        //获取分页信息
        PageInfo pageInfo = new PageInfo<>(list);
        System.out.println("total:" + pageInfo.getTotal());
        System.out.println("pages:" + pageInfo.getPages());
        System.out.println("pageSize:" + pageInfo.getPageSize());
        return list;
    }
}

测试

此前在项目编写过程中已经对可能出现的错误进行了总结，最后，对项目的功能进行测试，通过加@RestController注解将数据传输到浏览器中。
测试mybatis与springboot，浏览器输入http://localhost:8080/test，浏览器输出：

{"id":1,"name":"wanger","age":22}

分页测试，浏览器输入http://localhost:8080/list，浏览器输出：

[{"id":1,"name":"wanger","age":22},{"id":2,"name":"zhangsan","age":18}]

eclipse输出：

total:4
pages:2
pageSize:2

项目搭建完毕，具体代码参见github

本文参考了：
http://412887952-qq-com.iteye.com/blog/2392672
https://blog.csdn.net/rico_rico/article/details/79408474
https://blog.csdn.net/winter_chen001/article/details/77249029