动态查询省市县三级目录树（省、市、县分别存放在三张不同的表结构中），查询逻辑都在XML中完成 实体类

Mapper

public interface ProvinceMapper {
    public List<Province> getProvinceTree(Province province);
}

实体类

public class Province {
    private String code;
    private String belongCode;
    private String provinceName;
    @Transient // javax.persistence.Transient
    private List<City> cityList;
    ... 省略set/get方法
}
public class City {
    private String code;
    private String belongCode;
    private String cityName;  
    @Transient // javax.persistence.Transient
    private List<County> countyList;
    ... 省略set/get方法
}
public class County {
    private String code;
    private String belongCode;
    private String countyName;
    ... 省略set/get方法 
}

第一种方式：在XML中多表关联查询

<?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="com.springboot.mapper.ProvinceMapper" >
  <resultMap id="BaseProvinceResultMap" type="com.springboot.pojo.Province" >
    <result column="code" property="code" jdbcType="VARCHAR" />
    <result column="belong_code" property="belongCode" jdbcType="VARCHAR" />
    <result column="province_name" property="provinceName" jdbcType="VARCHAR" />
    <collection property="cityList" javaType="java.util.ArrayList" ofType="com.springboot.pojo.City" >
      <result column="city_name" property="cityName" jdbcType="VARCHAR" />
      <collection property="countyList" javaType="java.util.ArrayList" ofType="com.springboot.pojo.County" >
        <result column="county_name" property="countyName" jdbcType="VARCHAR" />
      </collection>
    </collection>
  </resultMap>
  <select id="getProvinceTree" parameterType="com.springboot.pojo.Province" resultMap="BaseProvinceResultMap">
    SELECT p2.province_name, city.city_name, county.county_name
     FROM (SELECT p1.code, p1.province_name
             FROM province p1
            WHERE p1.belong_code = #{ belongCode }) p2
      LEFT JOIN city
        ON p2.code = city.belong_code
      LEFT JOIN county
        ON city.code = county.belong_code
  </select> 
</mapper>

第二种方式：使用mybatis的collection递归查询

<?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="com.springboot.mapper.ProvinceMapper" >
  <resultMap id="BaseProvinceTreetMap" type="com.springboot.pojo.Province" >
    <result column="code" property="code" jdbcType="VARCHAR" />
    <result column="belong_code" property="belongCode" jdbcType="VARCHAR" />
    <result column="province_name" property="provinceName" jdbcType="VARCHAR" />
    <collection column="code" property="cityList" javaType="java.util.ArrayList" ofType="com.springboot.pojo.City" select="getCityTree" />
  </resultMap>
  <resultMap id="BaseCityTreeMap" type="com.springboot.pojo.City" >
    <result column="code" property="code" jdbcType="VARCHAR" />
    <result column="belong_code" property="belongCode" jdbcType="VARCHAR" />
    <result column="city_name" property="cityName" jdbcType="VARCHAR" />
    <collection column="code" property="countyList" javaType="java.util.ArrayList" ofType="com.springboot.pojo.County" select="getCountyTree" />
  </resultMap>
    <resultMap id="BaseCountyTreeMap" type="com.springboot.pojo.County" >
    <result column="code" property="code" jdbcType="VARCHAR" />
    <result column="belong_code" property="belongCode" jdbcType="VARCHAR" />
    <result column="county_name" property="countyName" jdbcType="VARCHAR" />
  </resultMap>
  
  <select id="getProvinceTree" parameterType="com.springboot.pojo.Province" resultMap="BaseProvinceTreetMap">
     SELECT code,belong_code,province_name FROM province WHERE belong_code = #{ belongCode }
  </select>
  <select id="getCityTree" resultMap="BaseCityTreeMap">
     SELECT code,belong_code,city_name FROM city WHERE belong_code = #{ belongCode }
  </select>
  <select id="getCountyTree" resultMap="BaseCountyTreeMap">
     SELECT code, belong_code, county_name FROM county WHERE belong_code = #{ belongCode }
  </select>
</mapper>