mybatis-plus 连表查询

一、mybatis

xml格式可以参考: https://www.cnblogs.com/wt7018/p/13333855.html

xml方法 失败，求大神指导

在springboot中使用mybaits注解的方式查询

1、根据查询的字段创建实现类

package com.wt.pojo;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

@Data
@AllArgsConstructor
@NoArgsConstructor
public class User2 {
    private String name;
    private int age;
    private String courseName;
}

2、在mapper文件夹下，创建方法

package com.wt.mapper;

import com.baomidou.mybatisplus.core.conditions.Wrapper;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.baomidou.mybatisplus.core.toolkit.Constants;
import com.wt.pojo.User;
import com.wt.pojo.User2;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Select;
import org.springframework.stereotype.Repository;

import java.util.List;

@Repository
public interface UserMapper extends BaseMapper<User> {
    @Select("SELECT user.name, user.age, course.course_name FROM user right join course on user.id = course.user_id WHERE id = #{id}")
    List<User2> getUserList(@Param("id") int id);
    
}

3、写get接口

    @GetMapping("/selectBy")
    public String selectMu(@RequestParam("id") int id){
        List<User2> userList = userMapper.getUserList(id);

        return JSON.toJSONString(userList);
    }