【Spring Boot】【Mybatis】Xmlベースで単一SQLのネストによるマッピング実装

package com.example.demo.repository;

import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Param;

import com.example.demo.entity.Country;

@Mapper
public interface DemoMapperXmlSepalate {

    Country selectCountry(@Param("id")Integer id);
    
}

<?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.example.demo.repository.DemoMapperXmlSepalate">
    
    <resultMap id="countryMap" type="com.example.demo.entity.Country" >
    
        <result column="country" property="country" />
        <result column="last_update" property="lastUpdate" />
        <association property="id" column="country_id" select="selectCountryId" />
        <collection property="city" column="country_id" select="selectCity" />
    
    </resultMap>
    <select
        id="selectCountry"
        resultMap="countryMap">
        SELECT *
        FROM
            country
        WHERE
            country_id = #{id}
    </select>
    
    <resultMap id="countryIdMap" type="com.example.demo.entity.CountryId" >
        <result column="country_id" property="countryId" />
    </resultMap>
    <select
        id="selectCountryId"
        resultMap="countryIdMap">
        SELECT *
        FROM
            country
        WHERE
            country_id = #{id}
    </select>
    
    
    <resultMap id="cityMap" type="com.example.demo.entity.City" >
        <result column="city_id" property="cityId" />
        <result column="city" property="city" />
        <result column="last_update" property="lastUpdate" />
        <collection property="address" column="city_id" select="selectAdress" />
    </resultMap>
    <select
        id="selectCity"
        resultMap="cityMap">
        SELECT *
        FROM
            city
        WHERE
            country_id = #{id}
    </select>
    
    <resultMap id="addressMap" type="com.example.demo.entity.Address" >
    <result column="address_id" property="addressId" />
        <result column="address" property="address" />
        <result column="address2" property="address2" />
        <result column="district" property="district" />
        <result column="postal_code" property="postalCode" />
        <result column="phone" property="phone" />
        <result column="last_update" property="lastUpdate" />
    </resultMap>
    <select
        id="selectAdress"
        resultMap="addressMap">
        SELECT *
        FROM
            address
        WHERE
            city_id = #{id}
    </select>
</mapper>