Mybatis一对多关联

目录

一对多的理解

​​​实体类

映射文件

测试类

一对多的理解

一个老师拥有多个学生

一个老师下面拥有一群学生(集合 )

​​​实体类

学生类

package com.lele.pojo;

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

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

教师类

package com.lele.pojo;

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

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

映射文件

接口

package com.lele.dao;

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

import java.util.List;

public interface TeacherMapper {
    Teacher selectStudent(@Param("aid") int id);
}

xml映射文件

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

测试类

 @Test
public void test03(){
     SqlSession session = MybatisUtil.getSession();
     TeacherMapper mapper = session.getMapper(TeacherMapper.class);
     Teacher teacher = mapper.selectStudent(1);
     System.out.println(teacher);
 }