mybatis一对多，多对一的代码实现（一步步添加代码实现）

想实现调试请先搭一个Mybatis连MySQL数据库的环境
附个我的GitHub链接（可能经常有改动，慎用）：https://github.com/Frank520lang/mybatis_liang.git

Navicat新建teacher和student两张数据表：

CREATE TABLE `teacher`
(
    `id`   INT(10) NOT NULL,
    `name` VARCHAR(30) DEFAULT NULL,
    PRIMARY KEY (`id`)
) ENGINE = INNODB
  DEFAULT CHARSET = utf8;

INSERT INTO teacher(`id`, `name`)
VALUES (1, '秦老师');

CREATE TABLE `student`
(
    `id`   INT(10) NOT NULL,
    `name` VARCHAR(30) DEFAULT NULL,
    `tid`  INT(10)     DEFAULT NULL,
    PRIMARY KEY (`id`),
    KEY `fktid` (`tid`),
    CONSTRAINT `fktid` FOREIGN KEY (`tid`) REFERENCES `teacher` (`id`)
) ENGINE = INNODB
  DEFAULT CHARSET = utf8;

INSERT INTO `student` (`id`, `name`, `tid`)
VALUES (1, '小明', 1);
INSERT INTO `student` (`id`, `name`, `tid`)
VALUES (2, '小红', 1);
INSERT INTO `student` (`id`, `name`, `tid`)
VALUES (3, '小张', 1);
INSERT INTO `student` (`id`, `name`, `tid`)
VALUES (4, '小李', 1);
INSERT INTO `student` (`id`, `name`, `tid`)
VALUES (5, '小王', 1);

对应的student表：

对应的teacher表：

一对多的实现：

对应的实体类：Student.class:

@Data
public class Student {
    private Integer id;
    private String name;
    //一对多
    private Integer tid;
}

对应的实体类：Teacher.class

@Data
public class Teacher {
    private Integer id;
    private String name;
    //一对多
    private List students;
}

对应的Mapper接口：TeacherMapper.java

public interface TeacherMapper extends baseMapper {
    //一对多（集合）
    public List manyToOne();
}

对应的mapper.xml文件：teacher.xml

    
        select s.id sid,s.name sname,s.tid sid,t.id tid,t.name tname from student s,teacher t;
    
    
        
        


        



        
    

    
        
        
        
    

测试类：

public class StudentMapperTest {
    @Resource
    private StudentMapper studentMapper;
    @Resource
    private TeacherMapper teacherMapper;
    @Test
    public void testOneToMany(){

        List teachers =teacherMapper.manyToOne();
        System.out.println("----------------------------");
        System.out.println("----------------------------");
        System.out.println("----------------------------");
        System.out.println(teachers.get(1));
        System.out.println("----------------------------");
        System.out.println("----------------------------");
        System.out.println("----------------------------");
        for (Teacher teacher : teachers) {
            System.out.println(teacher);
        }
        System.out.println("----------------------------");
        System.out.println("----------------------------");
        System.out.println("----------------------------");
    }
}

单元测试结果：