MyBatis的关联查询之自关联
自关联
一、entity实体类
public class City {
private Integer cid;
private String cname;
private Integer pid;
//自关联集合 代表的是当前City对象的自己集合
public List<City> childCitys;
public Integer getCid() {
return cid;
}
public void setCid(Integer cid) {
this.cid = cid;
}
public String getCname() {
return cname;
}
public void setCname(String cname) {
this.cname = cname;
}
public Integer getPid() {
return pid;
}
public void setPid(Integer pid) {
this.pid = pid;
}
public List<City> getChildCitys() {
return childCitys;
}
public void setChildCitys(List<City> childCitys) {
this.childCitys = childCitys;
}
@Override
public String toString() {
return "City{" +
"cid=" + cid +
", cname='" + cname + '\'' +
", pid=" + pid +
", childCitys=" + childCitys +
'}';
}
}二、dao层
//自关联 查询河南省下所有子集
public City getCityAndChild(Integer cid);
三、dao.xml 小配置
<!--自关联-->
<resultMap id="CityAndChildCity" type="com.marketsys.entity.City">
<id column="cid" property="cid"></id>
<result column="cname" property="cname"></result>
<result column="pid" property="pid"></result>
<collection property="childCitys" ofType="com.marketsys.entity.City" select="getCity" column="cid">
<id column="cid" property="cid"></id>
<result column="cname" property="cname"></result>
<result column="pid" property="pid"></result>
</collection>
</resultMap>
<select id="getCityAndChild" resultMap="CityAndChildCity">
select * from city where cid=#{cid}
</select>
<select id="getCity" resultMap="CityAndChildCity">
select * from city where pid=#{cid}
</select>
四、test测试类
SqlSession sqlSession= MybatisUtil.getSqlSession();
URoleTestDao mapper=sqlSession.getMapper(URoleTestDao.class); //自关联
@Test
public void test4(){
City city = mapper.getCityAndChild(410000);
System.out.println(city.toString());
}