spring-boot-realworld-example-app/src/main/resources/mapper/ArticleFavoritesQueryService.xml

<?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="io.spring.application.ArticleFavoritesQueryService">
    <select id="isUserFavorite" resultType="java.lang.Boolean">
        select count(1) from article_favorites where user_id = #{userId} and article_id = #{articleId}
    </select>
    <select id="articleFavoriteCount" resultType="java.lang.Integer">
        select count(1) from article_favorites where article_id = #{articleId}
    </select>
    <select id="articlesFavoriteCount" resultMap="favoriteCount">
        select A.id, count(AF.user_id) as favoriteCount from articles A
        left join article_favorites AF on A.id = AF.article_id
        where id in
        <foreach collection="ids" item="item" separator="," open="(" close=")">
            #{item}
        </foreach>
        group by A.id
    </select>
    <select id="userFavorites" resultType="java.lang.String">
        select
          A.id
        from articles A
        left join article_favorites AF on A.id = AF.article_id
        where id in
        <foreach collection="ids" item="item" separator="," open="(" close=")">
            #{item}
        </foreach>
        and AF.user_id = #{currentUser.id}
    </select>

    <resultMap id="favoriteCount" type="io.spring.application.ArticleFavoriteCount">
        <id column="id" property="id"/>
        <result column="favoriteCount" property="count"/>
    </resultMap>

</mapper>