查询导师 下面的所有 老师的信息！
创建实体类 和对应的数据库
/**
*导师的实体类
*/
public class Teacher {
private Integer id;
private String name;
//导师下所有的老师
private Set<Teacher> teachers; public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Set<Teacher> getTeachers() {
return teachers;
}
public void setTeachers(Set<Teacher> teachers) {
this.teachers = teachers;
}
public Teacher(Integer id, String name, Set<Teacher> teachers) {
super();
this.id = id;
this.name = name;
this.teachers = teachers;
}
public Teacher() {
super();
}
@Override
public String toString() {
return "Teacher [id=" + id + ", name=" + name + ", teachers="
+ teachers + "]";
}
}
创建对应的mapper文件和dao
public interface TeacherDao {
/**
* 根据导师的编号查询所有的老师信息
* 相当于递归查询
*/
List<Teacher> selectTeahcerByTid(Integer tId);
}
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-Mapper.dtd">
<mapper namespace="cn.bdqn.dao.TeacherDao"> <resultMap type="Teacher" id="teacherMap">
<id property="id" column="id"/>
<result property="name" column="name"/>
<!-- 设置关联集合的属性
select="selectTeahcerByTid"
因为查询的结果都是一样的 递归查询
column="id"
根据查询到的id再作为参数进行下一次的查询
-->
<collection property="teachers" ofType="Teacher"
select="selectTeahcerByTid" column="id"/>
</resultMap> <select id="selectTeahcerByTid" resultMap="teacherMap">
select id,name from teacher where tid=#{xxx}
</select> </mapper>
mybatis.xml中管理mapper文件
<!-- 加载映射文件信息 -->
<mappers>
<mapper resource="cn/bdqn/dao/TeacherMapper.xml" />
</mappers>
测试代码
package cn.bdqn.test; import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map; import org.apache.ibatis.session.SqlSession;
import org.junit.After;
import org.junit.Before;
import org.junit.Test; import cn.bdqn.bean.Teacher;
import cn.bdqn.dao.TeacherDao;
import cn.bdqn.util.SessionUtil; public class TeacherTest {
TeacherDao dao;
SqlSession session; @Before
public void before() {
// 因为需要关闭session 需要把session提取出去
session = SessionUtil.getSession();
dao = session.getMapper(TeacherDao.class);
} @After
public void after() {
if (session != null) {
session.close();
}
} /**
* 根据导师的id查询出对应的所有老师信息
*/
@Test
public void test1() {
List<Teacher> list = dao.selectTeahcerByTid(1);
for (Teacher teacher : list) {
System.out.println(teacher);
}
} }
查询导师 的信息 以及 下面的所有 老师的信息！
修改dao 和 mapper文件
public interface TeacherDao {
/**
* 根据导师的编号查询所有的老师信息以及自身的信息
*/
Teacher selectTeahcerById(Integer tId);
}
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-Mapper.dtd">
<mapper namespace="cn.bdqn.dao.TeacherDao"> <select id="selectTeahcerByTid" resultMap="teacherMap">
select id,name from teacher where tid=#{xxx}
<!--#{xxx} 就是再根据tid查询对应的子项 -->
</select> <resultMap type="Teacher" id="teacherMap">
<id property="id" column="id"/>
<result property="name" column="name"/>
<!-- 设置关联集合的属性
select="selectTeahcerByTid"
因为查询的结果都是一样的 递归查询
column="id"
根据查询到的id再作为tid进行下一次的查询
-->
<collection property="teachers" ofType="Teacher"
select="selectTeahcerByTid" column="id"/>
</resultMap> <select id="selectTeahcerById" resultMap="teacherMap">
<!--先查询出 自身的信息 -->
select id,name from teacher where id=#{xxx}
</select> </mapper>
修改测试类
/**
* 根据导师的id查询出对应的所有老师信息
*/
@Test
public void test1() {
Teacher teacher = dao.selectTeahcerById(1);
System.out.println(teacher);
}