方法一： 結果巢狀處理

子查詢的由於比較繁瑣就不寫了 具體可以看上面的多對一 實現過程基本差不多

• 這裡的關鍵就是配置檔案的編寫collection標籤的使用

第一步：實體類的編寫

@Data
@AllArgsConstructor
@NoArgsConstructor
public class Student implements Serializable {
  private Integer id;
  private String name;
  private Integer tid;
  
}

@Data
@AllArgsConstructor
@NoArgsConstructor
public class Teacher implements Serializable {
 
​
  private Integer id;
  private String name;
  private List<Student> students;
}

第二步：mapper介面的編寫

//獲取一個老師及其下的所有學生
Teacher findTeacher(@Param("id") Integer id )throws Exception;

第三步: 配置檔案編寫

• 在一對多中，採用的是collection標籤 ofType指定相應的泛型型別

<resultMap id="TeacherMap" type="Teacher">
  <result property="id" column="tid"></result>
 
  <result property="name" column="tname"></result>
  <collection property="students" ofType="Student" >
    <result property="name" column="sname"></result>
    <result property="id" column="id"></result>
    <result property="tid" column="tid"></result>
 
  </collection>
</resultMap>
​
<select id="findTeacher" resultMap="TeacherMap">
   select t.id tid,t.name tname,s.name sname,s.id
   from teacher t,student s
   where s.tid=t.id and t.id=#{id}
</select>

第四步：編寫測試類

Test
public void findTeachers() throws Exception {
  SqlSession sqlSession = MyBatisUtil.getSqlSession();
​
  TeacherMapper mapper = sqlSession.getMapper(TeacherMapper.class);
​
  Teacher teacher = mapper.findTeacher(1);
​
  System.out.println(teacher);
​
  sqlSession.close();
}

--------------------------------測試成功------------------------------------