mybatis-plus分页查询的实现示例

所属分类：软件编程 / java 阅读数： 44

收藏 0赞 0分享

引入依赖：

<!-- 引入mybatisPlus -->
  　　<dependency>
   <groupId>com.baomidou</groupId>
   <artifactId>mybatis-plus-boot-starter</artifactId>
   <version>3.2.0</version>
  </dependency>
  <!-- 引入mysql驱动包 -->
  <dependency>
   <groupId>mysql</groupId>
   <artifactId>mysql-connector-java</artifactId>
   <version>5.1.27</version>
  </dependency>
  <!-- 引入Druid依赖，阿里巴巴所提供的数据源 -->
  <dependency>
   <groupId>com.alibaba</groupId>
   <artifactId>druid</artifactId>
   <version>1.0.29</version>
　　　　</dependency>

在application.yml配置

spring:
 datasource:
 type: com.alibaba.druid.pool.DruidDataSource
 driver-class-name: com.mysql.jdbc.Driver
 url: jdbc:mysql://127.0.0.1:3306/test?useUnicode=true&characterEncoding=UTF-8
 username: root
 password: 123456

在启动类上面添加@MapperScan注解，扫描mapper包

@SpringBootApplication
@MapperScan("com.qiao.demo02.mapper")
public class SpringbootDemo02Application {

 public static void main(String[] args) {
  SpringApplication.run(SpringbootDemo02Application.class, args);
 }

}

新建User和UserMapper

user类

@Data
public class User {
 @TableId
 private Integer userId;
 private String userName;
 private Integer userAge;
 private String userEmail;
}

UserMapper接口

 public interface UserMapper extends BaseMapper<User> {
 
 }

最重要的是继承BaseMapper<E>接口：里面声明了很强大的CRUD方法

public interface BaseMapper<T> extends Mapper<T> {
 int insert(T entity);

 int deleteById(Serializable id);

 int deleteByMap(@Param("cm") Map<String, Object> columnMap);

 int delete(@Param("ew") Wrapper<T> wrapper);

 int deleteBatchIds(@Param("coll") Collection<? extends Serializable> idList);

 int updateById(@Param("et") T entity);

 int update(@Param("et") T entity, @Param("ew") Wrapper<T> updateWrapper);

 T selectById(Serializable id);

 List<T> selectBatchIds(@Param("coll") Collection<? extends Serializable> idList);

 List<T> selectByMap(@Param("cm") Map<String, Object> columnMap);

 T selectOne(@Param("ew") Wrapper<T> queryWrapper);

 Integer selectCount(@Param("ew") Wrapper<T> queryWrapper);

 List<T> selectList(@Param("ew") Wrapper<T> queryWrapper);

 List<Map<String, Object>> selectMaps(@Param("ew") Wrapper<T> queryWrapper);

 List<Object> selectObjs(@Param("ew") Wrapper<T> queryWrapper);

 IPage<T> selectPage(IPage<T> page, @Param("ew") Wrapper<T> queryWrapper);

 IPage<Map<String, Object>> selectMapsPage(IPage<T> page, @Param("ew") Wrapper<T> queryWrapper);
}

分页查询

这点官方文档讲的也很详细：https://mp.baomidou.com/guide/page.html

新建一个config包，在里面建一个MybatisPlus配置类返回一个分页拦截器

package com.qiao.demo02.config;

@Configuration
@ConditionalOnClass(value = {PaginationInterceptor.class})
public class MybatisPlusConfig {
 @Bean
 public PaginationInterceptor paginationInterceptor() {
  PaginationInterceptor paginationInterceptor = new PaginationInterceptor();
  return paginationInterceptor;
 }
}

这样就能使用mybatis的分页功能了

Junit测试

@Resource
 private UserMapper userMapper;
 @Test
 public void queryUserForPage(){
  IPage<User> userPage = new Page<>(2, 2);//参数一是当前页，参数二是每页个数
  userPage = userMapper.selectPage(userPage, null);
  List<User> list = userPage.getRecords();
  for(User user : list){
   System.out.println(user);
  }
 }

Controller返回json串

先定义一个包装类UserVo，用来保存分页所需要的数据

package com.qiao.demo02.vo;

@Data
public class UserVo {
 private Integer current;
 private Integer size;
 private Long total;
 private List<User> userList;
}

然后在控制器编写代码，这里省略了service层，实际开发业务代码写在service层，Controller只负责：接受参数、调用service层方法处理业务逻辑，返回结果

Controller类贴上了@RestController注解

 @GetMapping("queryUser")
 public UserVo queryList(Integer current, Integer size) {
  /**
   * 这些代码应该写在service层
   */
  UserVo userVo = new UserVo();
  IPage<User> page = new Page<>(current, size);
  userMapper.selectPage(page, null);
  userVo.setCurrent(current);
  userVo.setSize(size);
  userVo.setTotal(page.getTotal());
  userVo.setUserList(page.getRecords());
  return userVo;
 }

附上结果，前端直接处理json数据即可