MybatisPlus 多表关联查询带分页

demo：https://download.csdn.net/download/caidingnu/12064636

1、目录结构

2、Controller

package com.example.mybatisplustest.controller;

import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.baomidou.mybatisplus.core.metadata.IPage;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.example.mybatisplustest.entity.UniData;
import com.example.mybatisplustest.entity.User;
import com.example.mybatisplustest.mapper.PageDataMapper;
import com.example.mybatisplustest.mapper.UserMapper;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.HashMap;
import java.util.Map;

/**
 * desc： plus 分页方式
 * author CDN
 * create 2019-12-27 21:37
 * version 1.0.0
 */
@RestController
public class PageDataController {
    @Autowired
    PageDataMapper pageDataMapper;

    @Autowired
    UserMapper userMapper;

    /**
     * desc:  注解方式（关联分页查询）
     * param:
     * return:
     * author: CDN
     * date: 2019/12/27
     */
    @RequestMapping("/annotationsPage")
    public Object annotationsPage() {
        IPage page=new Page<>(1, 2);
        Map map=new HashMap();
        map.put("userId", 1);
        IPage all = pageDataMapper.annotationsPage(page,map);
        return all;
    }


    /**
     * desc:  provider （关联分页查询）
     * param:
     * return:
     * author: CDN
     * date: 2019/12/27
     */
    @RequestMapping("/providerPage")
    public Object providerPage() {
        IPage page=new Page<>(1, 2);
        Map map=new HashMap();
        map.put("userId", 1);
        IPage all = pageDataMapper.providerPage(page,map);
        return all;
    }


    /**
     * desc:  xml方式（关联分页查询）
     * param:
     * return:
     * author: CDN
     * date: 2019/12/27
     */
    @RequestMapping("/xmlPage")
    public Object xmlPage() {
        IPage page=new Page<>(1, 2);
        Map map=new HashMap();
        map.put("userId", 1);
        IPage all = pageDataMapper.xmlPage(page,map);
        return all;
    }


    /**
     * desc:  常规方式(单表 user表)
     * param:
     * return:
     * author: CDN
     * date: 2019/12/27
     */
    @RequestMapping("/commonPage")
    public Object commonPage() {
        IPage page=new Page<>(1, 2);
        QueryWrapper queryWrapper=new QueryWrapper<>();
        queryWrapper.eq("user_id", 1);
        IPage all = userMapper.selectPage(page,queryWrapper);
        return all;
    }


}

3、UniData 实体

package com.example.mybatisplustest.entity;

/**
 * desc：
 * author CDN
 * create 2019-12-27 21:10
 * version 1.0.0
 */
public class UniData {

    private String name;

    private String password;

    private String nickName;

    private Integer age;

    private Integer roleId;

    private String role;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getNickName() {
        return nickName;
    }

    public void setNickName(String nickName) {
        this.nickName = nickName;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public Integer getRoleId() {
        return roleId;
    }

    public void setRoleId(Integer roleId) {
        this.roleId = roleId;
    }

    public String getRole() {
        return role;
    }

    public void setRole(String role) {
        this.role = role;
    }
}

4、Mapper

package com.example.mybatisplustest.mapper;

import com.baomidou.mybatisplus.core.metadata.IPage;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.example.mybatisplustest.entity.UniData;
import com.example.mybatisplustest.mapper.provider.UniDataProvider;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Select;
import org.apache.ibatis.annotations.SelectProvider;

import java.util.Map;

/**
 * desc:
 * author caidingnu
 * create 2019/12/27
 * version 1.0.0
 */
public interface PageDataMapper {

    /**
     * 注解方式分页
     *
     * @param page
     * @param map
     * @return
     */
    @Select("SELECT user.name,user.password,USER.nick_name as nickName,USER.age,role.role_id as roleId,role.role " +
            "FROM user INNER JOIN role ON `user`.user_id = role.role_id where user.user_id = #{map.userId}")
    IPage annotationsPage(IPage page, @Param("map") Map map);

    /**
     * provider 方式分页
     *   ☆☆☆☆☆☆☆ 重点： page必须放在第一个参数，否则无法分页或者报错 ☆☆☆☆☆☆☆☆
     * @param page
     * @param map
     * @return
     */
    @SelectProvider(type = UniDataProvider.class, method = "providerPage")
    IPage providerPage(IPage page, @Param("map") Map map);

    /**
     *  xml 方式分页
     * @param page
     * @param map
     * @return
     */
    IPage xmlPage(IPage page, @Param("map") Map map);
}

5、UniDataProvider

package com.example.mybatisplustest.mapper.provider;

import com.baomidou.mybatisplus.core.metadata.IPage;
import com.example.mybatisplustest.entity.UniData;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.jdbc.SQL;

import java.util.Map;

/**
 * desc：
 * author CDN
 * create 2019-12-27 22:20
 * version 1.0.0
 */
public class UniDataProvider {


    /**
     * desc:
     * param:
     * return:
     * author: CDN
     * date: 2019/12/27
     */
    public String providerPage(Map map) {
        SQL sql = new SQL();
        sql.SELECT("user.name,user.password,USER.nick_name as nickName,USER.age,role.role_id as roleId,role.role " +
                "FROM user INNER JOIN role ON `user`.user_id = role.role_id where user.user_id = #{map.userId}");
        return sql.toString();
    }
}

6、PageDataMapper

   
       SELECT user.name,user.password,USER.nick_name as nickName,USER.age,role.role_id as roleId,role.role " +
            "FROM user INNER JOIN role ON `user`.user_id = role.role_id where user.user_id = #{map.userId}