最全的Spring-Boot集成Mybatis-Plus教程

2014 年 5 月 9 日

开发pybbs最后选用的是Mybatis-Plus框架，不得不说， 真香
，想当初接触过jpa后，跟别人安利，说jpa多好用多简单，后来在公司项目里用时，随着项目渐渐复杂起来，多个表关联查询是真的不爽，哎呀， xml真香

这一篇博客来总结一下使用mybatis-plus的相关配置以及mybatis的一些用法

创建项目

普通的spring-boot项目，在start.spring.io或者使用idea创建都行，相关依赖如下
我这版本用的springboot版本是 2.1.4

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



  org.springframework.boot
  spring-boot-devtools
  runtime


  mysql
  mysql-connector-java
  runtime


  org.projectlombok
  lombok
  true


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



  com.baomidou
  mybatis-plus-boot-starter
  3.1.0

建表

CREATE TABLE `topic` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `title` varchar(255) DEFAULT NULL,
  `content` varchar(255) DEFAULT NULL,
  `tag` varchar(255) DEFAULT NULL,
  `in_time` datetime DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=14 DEFAULT CHARSET=utf8;

插入一些数据

INSERT INTO `topic` (`id`, `title`, `content`, `tag`, `in_time`)
VALUES
    (1, 'title1', 'content1', 'tag1', '2019-04-15 09:33:35'),
    (2, 'title2', 'content2', 'tag2', '2019-04-15 09:33:35'),
    (3, 'title3', 'content3', 'tag3', '2019-04-15 09:33:35'),
    (4, 'title4', 'content4', 'tag4', '2019-04-15 09:33:35'),
    (5, 'title4', 'content4', 'tag4', '2019-04-15 09:33:35'),
    (6, 'title4', 'content4', 'tag4', '2019-04-15 09:33:35'),
    (7, 'title4', 'content4', 'tag4', '2019-04-15 09:33:35'),
    (8, 'title4', 'content4', 'tag4', '2019-04-15 09:33:35'),
    (9, 'title4', 'content4', 'tag4', '2019-04-15 09:33:35'),
    (10, 'title4', 'content4', 'tag4', '2019-04-15 09:33:35'),
    (11, 'title4', 'content4', 'tag4', '2019-04-15 09:33:35'),
    (12, 'title4', 'content4', 'tag4', '2019-04-15 09:33:35'),
    (13, 'title4', 'content4', 'tag4', '2019-04-15 09:33:35');

原链接文： https://tomoya92.github.io/2019/04/15/spring-boot-mybatis-plus-tutorial/

创建实体类

@Data
public class Topic {

  @TableId(type = IdType.AUTO)
  private Integer id;

  private String title;
  private String content;
  private String tag;
  private Date inTime;

}

创建mapper

public interface TopicMapper extends BaseMapper {

}

创建service

@Service
@Transactional
public class TopicService {

  @Autowired
  private TopicMapper topicMapper;

  public List list() {
    return topicMapper.selectList(new QueryWrapper());
  }

}

创建controller

@RestController
public class TopicController {

  @Autowired
  private TopicService topicService;

  @GetMapping("/")
  public Object list() {
    return topicService.list();
  }
}

添加包扫描

最后在启动类 MybatisPlusDemoApplication.java
上加上扫描包的注解，如下

@SpringBootApplication
@MapperScan("com.example.mybatisplusdemo..mapper")
public class MybatisPlusDemoApplication {

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

}

测试

curl http://localhost:808/

[{"id":1,"title":"title1","content":"content1","tag":"tag1","inTime":"2019-04-15T14:33:35.000+0000"},
{"id":2,"title":"title2","content":"content2","tag":"tag2","inTime":"2019-04-15T14:33:35.000+0000"},
{"id":3,"title":"title3","content":"content3","tag":"tag3","inTime":"2019-04-15T14:33:35.000+0000"},
{"id":4,"title":"title4","content":"content4","tag":"tag4","inTime":"2019-04-15T14:33:35.000+0000"},
{"id":5,"title":"title4","content":"content4","tag":"tag4","inTime":"2019-04-15T14:33:35.000+0000"},
{"id":6,"title":"title4","content":"content4","tag":"tag4","inTime":"2019-04-15T14:33:35.000+0000"},
{"id":7,"title":"title4","content":"content4","tag":"tag4","inTime":"2019-04-15T14:33:35.000+0000"},
{"id":8,"title":"title4","content":"content4","tag":"tag4","inTime":"2019-04-15T14:33:35.000+0000"},
{"id":9,"title":"title4","content":"content4","tag":"tag4","inTime":"2019-04-15T14:33:35.000+0000"},
{"id":10,"title":"title4","content":"content4","tag":"tag4","inTime":"2019-04-15T14:33:35.000+0000"},
{"id":11,"title":"title4","content":"content4","tag":"tag4","inTime":"2019-04-15T14:33:35.000+0000"},
{"id":12,"title":"title4","content":"content4","tag":"tag4","inTime":"2019-04-15T14:33:35.000+0000"},
{"id":13,"title":"title4","content":"content4","tag":"tag4","inTime":"2019-04-15T14:33:35.000+0000"}]

上面的一些用法在mybatis-plus官网上都能找到，都是基本用法，但开发项目不可能都是简单的crud，下面来说说一些高级的用法

xml怎么配置

mybatis-plus里内置的crud都给封装好了，都在 BaseMapper
接口里，包括CRUD，分页，那如果我要自定义查询，返回字段不是整个实体类的字段怎么办呢？
可以通过定义xml文件来查询，方法如下

在 TopicMapper.java
类的包下，创建一个 TopicMapper.xml
文件，填上下面内容




  
  
      
      
      
      
      
  

  
  
      id, title, content, tag, in_time

在这个xml文件里定义一个方法

  select  from topic where title = '${title}'

接原链文： https://tomoya92.github.io/2019/04/15/spring-boot-mybatis-plus-tutorial/

对应的，在 TopicMapper.java
里也要加上相应的接口

public interface TopicMapper extends BaseMapper {
  Topic selectByTitle(@Param("title") String title);
}

在service里就可以调用了，controller里再调用service里的方法，然后测试

curl http://localhost:8080/selectByTitle?title=titl1

{"id":1,"title":"title1","content":"content1","tag":"tag1","inTime":"2019-04-15T05:00:00.000+0000"}

可以看到上面xml里定义方法时用到的返回类型是定义好的映射 resultMap="BaseResultMap"
和通用查询结果列
，那如果我想返回一个map怎么办呢？

将 resultMap="BaseResultMap"
换成 resultType="map"
，查询语句里写上要查询的字段即可

自定义返回结果

上面最后提到返回一个map，这需求也很常见，比如一个表字段有10个，我只想要5个，那这时候再去定义通用查询结果列就不太好了，两个还好，多了xml就会很乱，所以map是最适合的方式，下面来定义一个查询看下效果

  select id, title, in_time from topic

上面定义了一个方法，返回用的是 map
，查询字段有 id, title
， BaseMapper.java
里接口定义如下

public interface TopicMapper extends BaseMapper {
  List selectTitleList();
}

写好service,controller，测试

curl http://localhost:8080/selectTitleList

[{"in_time":"2019-04-15T14:33:35.000+0000","id":1,"title":"title1"},
{"in_time":"2019-04-15T14:33:35.000+0000","id":2,"title":"title2"},
{"in_time":"2019-04-15T14:33:35.000+0000","id":3,"title":"title3"},
{"in_time":"2019-04-15T14:33:35.000+0000","id":4,"title":"title4"},
{"in_time":"2019-04-15T14:33:35.000+0000","id":5,"title":"title4"},
{"in_time":"2019-04-15T14:33:35.000+0000","id":6,"title":"title4"},
{"in_time":"2019-04-15T14:33:35.000+0000","id":7,"title":"title4"},
{"in_time":"2019-04-15T14:33:35.000+0000","id":8,"title":"title4"},
{"in_time":"2019-04-15T14:33:35.000+0000","id":9,"title":"title4"},
{"in_time":"2019-04-15T14:33:35.000+0000","id":10,"title":"title4"},
{"in_time":"2019-04-15T14:33:35.000+0000","id":11,"title":"title4"},
{"in_time":"2019-04-15T14:33:35.000+0000","id":12,"title":"title4"},
{"in_time":"2019-04-15T14:33:35.000+0000","id":13,"title":"title4"}]

map转驼峰

上面查询结果可以看到，返回的确实是map，没有问题，但java类中的驼峰没有转回来呀，这样就不友好了，比如前端定义好了返回结果类，本来查询列表好好的，但换成详细查询的时候，字段收不到了，找了半天原来是字段变了，又是一场撕逼
mybatis我不知道有没有办法解决，但mybatis-plus人家很用心呀，一个配置就解决了这个问题

创建 MybatisPlusConfig.java
配置类，添加上下面配置即可实现 map转驼峰
和分页功能，分页功能下面再介绍，这里就先配置上

@Configuration
@MapperScan("com.example.mybatisplusdemo..mapper")
public class MybatisPlusConfig {

  @Bean("mybatisSqlSession")
  public SqlSessionFactory sqlSessionFactory(@Qualifier("dataSource") DataSource dataSource) throws Exception {
    MybatisSqlSessionFactoryBean sqlSessionFactory = new MybatisSqlSessionFactoryBean();
    MybatisConfiguration configuration = new MybatisConfiguration();
    configuration.setDefaultScriptingLanguage(MybatisXMLLanguageDriver.class);
    configuration.setJdbcTypeForNull(JdbcType.NULL);
    //*注册Map 下划线转驼峰*
   configuration.setObjectWrapperFactory(new MybatisMapWrapperFactory());

    // 添加数据源
    sqlSessionFactory.setDataSource(dataSource);

    sqlSessionFactory.setConfiguration(configuration);

    // 添加分页插件，这里有个坑
    PaginationInterceptor paginationInterceptor = new PaginationInterceptor();
    sqlSessionFactory.setPlugins(new Interceptor[]{paginationInterceptor});

    return sqlSessionFactory.getObject();
  }
}

加上这个配置类后，Mapper扫描注解顺便也从启动类上移到这个类上配置，然后再次启动项目，测试

curl http://localhost:8080/selectTitleList

[{"inTime":"2019-04-15T14:33:35.000+0000","id":1,"title":"title1"},
{"inTime":"2019-04-15T14:33:35.000+0000","id":2,"title":"title2"},
{"inTime":"2019-04-15T14:33:35.000+0000","id":3,"title":"title3"},
{"inTime":"2019-04-15T14:33:35.000+0000","id":4,"title":"title4"},
{"inTime":"2019-04-15T14:33:35.000+0000","id":5,"title":"title4"},
{"inTime":"2019-04-15T14:33:35.000+0000","id":6,"title":"title4"},
{"inTime":"2019-04-15T14:33:35.000+0000","id":7,"title":"title4"},
{"inTime":"2019-04-15T14:33:35.000+0000","id":8,"title":"title4"},
{"inTime":"2019-04-15T14:33:35.000+0000","id":9,"title":"title4"},
{"inTime":"2019-04-15T14:33:35.000+0000","id":10,"title":"title4"},
{"inTime":"2019-04-15T14:33:35.000+0000","id":11,"title":"title4"},
{"inTime":"2019-04-15T14:33:35.000+0000","id":12,"title":"title4"},
{"inTime":"2019-04-15T14:33:35.000+0000","id":13,"title":"title4"}]

再看看结果， in_time
已经从下划线转成驼峰 inTime
命名了，可喜可贺可喜可贺

BaseMapper分页

分页分两种，一种是BaseMapper接口内置的分页接口，直接调用即可，使用如下

文接原链： https://tomoya92.github.io/2019/04/15/spring-boot-mybatis-plus-tutorial/

在service里直接调用方法

public IPage selectWithPage(Integer pageNo, Integer pageSize) {
  QueryWrapper wrapper = new QueryWrapper();
  IPage iPage = new Page(pageNo, pageSize);
  return topicMapper.selectPage(iPage, wrapper);
}

测试 curl http://localhost:8080/selectWithPage?pageNo=1&pageSize=5

{"records":[{"id":1,"title":"title1","content":"content1","tag":"tag1","inTime":"2019-04-15T14:33:35.000+0000"},
{"id":2,"title":"title2","content":"content2","tag":"tag2","inTime":"2019-04-15T14:33:35.000+0000"},
{"id":3,"title":"title3","content":"content3","tag":"tag3","inTime":"2019-04-15T14:33:35.000+0000"},
{"id":4,"title":"title4","content":"content4","tag":"tag4","inTime":"2019-04-15T14:33:35.000+0000"},
{"id":5,"title":"title4","content":"content4","tag":"tag4","inTime":"2019-04-15T14:33:35.000+0000"}],
"total":13,"size":5,"current":1,"searchCount":true,"pages":3}

自定义查询分页

上面说到了使用自定义查询时可以指定查询字段，然后返回map即可，那分页怎么办？

mybatis-plus里有一个 IPage
接口，通过这个接口来封装分页信息，用法如下
在xml里定义查询方法

  select id, title, in_time from topic

在 BaseMapper.java
里定义接口

public interface TopicMapper extends BaseMapper {
  IPage selectMapWithPage(IPage iPage);
}

TopicService.java
里封装 IPage 对象然后调用接口

public IPage selectMapWithPage(Integer pageNo, Integer pageSize) {
  IPage iPage = new Page(pageNo, pageSize);
  iPage = topicMapper.selectMapWithPage(iPage);
  return iPage;
}

测试 curl http://localhost:8080/selectMapWithPage?pageNo=1&pageSize=5

{"records":[{"inTime":"2019-04-15T14:33:35.000+0000","id":1,"title":"title1"},
{"inTime":"2019-04-15T14:33:35.000+0000","id":2,"title":"title2"},
{"inTime":"2019-04-15T14:33:35.000+0000","id":3,"title":"title3"},
{"inTime":"2019-04-15T14:33:35.000+0000","id":4,"title":"title4"},
{"inTime":"2019-04-15T14:33:35.000+0000","id":5,"title":"title4"}],
"total":13,"size":5,"current":1,"searchCount":true,"pages":3}

注意

在xml文件里写的sql语句不要在最后带上 ;
，因为有些分页查询会自动拼上 limit 0, 10;
这样的sql语句，如果你在定义sql的时候已经加上了 ;
，调用这个查询的时候就会报错了
往xml文件里的查询方法里传参数要带上 @Param("")
注解，这样mybatis才认，否则会报错
分页中传的pageNo可以从0或者1开始，查询出的结果是一样的，这一点不像jpa里必须是从0开始才是第一页

参考

写博客不易，转载请保留原文链接，谢谢!
原文链接:

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9	10	11	12	13	14	15
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演道网

最全的Spring-Boot集成Mybatis-Plus教程

创建项目

建表

创建实体类

创建mapper

创建service

创建controller

添加包扫描

测试

xml怎么配置

自定义返回结果

map转驼峰

BaseMapper分页

自定义查询分页

注意

参考

About The Author

peace

创建项目

建表

创建实体类

创建mapper

创建service

创建controller

添加包扫描

测试

xml怎么配置

自定义返回结果

map转驼峰

BaseMapper分页

自定义查询分页

注意

参考

Related Posts

About The Author

peace