mybatis-plus分页查询的实现示例

按照官方文档进行的配置：快速开始|mybatis-plus

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 *

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

来源：https://www.cnblogs.com/seekknowledge/p/11734955.html