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 +

                '}';

    }

}

//自关联  查询河南省下所有子集

    public City getCityAndChild(Integer cid);

<!--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>

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());

    }