mybatis-plus分頁查詢

在springboot中整合mybatis-plus

　　按照官方文檔進行的配置：快速開始|mybatis-plus

　　引入依賴：

<!-- 引入mybatisPlus -->
     　　<dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.2.0</version>
        </dependency>
        <!-- 引入mysql驅動包 -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.27</version>
        </dependency>
        <!-- 引入Druid依賴，阿里巴巴所提供的數據源 -->
        <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

　　在啟動類上面添加@MapperScan注解，掃描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類

@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> {

}

　　最重要的是繼承BaseMapper<E>接口：里面聲明了很強大的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);
}

分頁查詢

　　這點官方文檔講的也很詳細：https://mp.baomidou.com/guide/page.html

　　新建一個config包，在里面建一個MybatisPlus配置類 返回一個分頁攔截器

package com.qiao.demo02.config;

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

 

　　這樣就能使用mybatis的分頁功能了

　　Junit測試

 @Resource
    private UserMapper userMapper;
    @Test
    public void queryUserForPage(){
        IPage<User> userPage = new Page<>(2, 2);//參數一是當前頁，參數二是每頁個數
        userPage = userMapper.selectPage(userPage, null);
        List<User> list = userPage.getRecords();
        for(User user : list){
            System.out.println(user);
        }
    }

　　Controller返回json串

　　　　先定義一個包裝類UserVo，用來保存分頁所需要的數據

package com.qiao.demo02.vo;

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

　　　　然后在控制器編寫代碼，這里省略了service層，實際開發業務代碼寫在service層，Controller只負責：接受參數、調用service層方法處理業務邏輯，返回結果

　　　　Controller類貼上了@RestController注解

 

@GetMapping("queryUser")
    public UserVo queryList(Integer current, Integer size) {
        /**
         * 這些代碼應該寫在service層
         */
        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;
    }

　　　　附上結果，前端直接處理json數據即可