MyBatis：一对多(狂神)

 

 

 

 

 

db.properties：

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/mybatis?useSSL=&useUnicode=true&characterEncoding=utf-8
username=root
password=123456

 mybatis-config.xml:

Student：

package com.kuang.pojo;

import lombok.Data;

@Data
public class Student {
    private int id;
    private String name;
    private int tid;
}

Teacher：

package com.kuang.pojo;

import lombok.Data;

import java.util.List;

@Data
public class Teacher {
    private int id;
    private String name;

    //一个老师拥有多个学生
    private List students;
}

TeacherMapper：

package com.kuang.dao;

import com.kuang.pojo.Teacher;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Select;

import java.util.List;

public interface TeacherMapper {


    //获取指定老师下所有的学生及老师的信息
    Teacher getTeacher(@Param("tid") int id);

    Teacher getTeacher2(@Param("tid") int id);
}

TeacherMapper.xml：

    


    
        select s.id sid,s.name sname,t.name tname,t.id tid
        from student1 s,teacher t
        where s.tid=t.id and t.id=#{tid}
    
    
        
        
        
        
            
            
            
        
    



    
        select  * from mybatis.teacher where id=#{tid}
    
    
        
        
        
    

    
        select * from mybatis.student1 where tid=#{id}
    

MyTest:

import com.kuang.dao.TeacherMapper;
import com.kuang.pojo.Teacher;
import com.kuang.utils.MybaitsUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class MyTest {
    //按结果集查询
    @Test
    public void test1(){
        SqlSession sqlSession= MybaitsUtils.getSqlSession();
        TeacherMapper mapper = sqlSession.getMapper(TeacherMapper.class);
        Teacher teacher = mapper.getTeacher(1);
        System.out.println(teacher);
        sqlSession.close();
    }
    //按嵌套查询
    @Test
    public void test2(){
        SqlSession sqlSession= MybaitsUtils.getSqlSession();
        TeacherMapper mapper = sqlSession.getMapper(TeacherMapper.class);
        Teacher teacher = mapper.getTeacher2(1);
        System.out.println(teacher);
        sqlSession.close();
    }
}

test1:

 

test2: