需求，使用分布查询，查询出指定老师信息，并把指定老师包含哪些学生也查出来

第一步：mapper接口

教师mapper

[code]/**
* 根据教师id查询指定的教师
* @param teacherId
* @return
*/
Teacher getTeacherWithId(Integer teacherId);

学生mapper

[code]/**
* 根据教师的id，查询教师下的所有学生
* @param teacherId
* @return
*/
List<Student> getStudentByTeacherId(Integer teacherId);

第二步：mapper.xml中SQL语句

teacher的sql：这里是使用resoultMap进行的分布查询

[code]<resultMap id="getTeacherWithIdMapper" type="com.ctbu.domain.Teacher">
<id property="teacherId" column="teacherId"/>
<result property="teacherName" column="teacherName"/>
<collection property="students" ofType="Student" select="com.ctbu.mapper.StudentMapper.getStudentByTeacherId" column="teacherId"/>

</resultMap>
<select id="getTeacherWithId" resultMap="getTeacherWithIdMapper">
select * from `teacher` where teacherId = #{teacherId};
</select>

student的sql：这里使用了范围查询，先传入teacher的id，根据teacherId查询出对应的学生id，再根据学生id查询出具体的学生信息

[code]<select id="getStudentByTeacherId" resultType="com.ctbu.domain.Student">
select * from `student` where
studentId in (select studentId from
`teacher_student` where teacherId=#{teacherId});
</select>

第三步：测试类

[code]@Test
public void test2(){
SqlSession session = MyUtils.openSession();
TeacherMapper teacherMapper = session.getMapper(TeacherMapper.class);
Teacher teacher = teacherMapper.getTeacherWithId(1);
System.out.println(teacher);

session.close();
}