iBatis 1:N mapping

게시판 시스템에 Article과 ArticleFile이라는 객체가 있고 이들이 1:N의 관계가 있다면 Article에는 아래와 같은 attribute이 존재할 것이다.

private Collection articleFiles;

이러한 경우 Article을 읽을 때 n개의 ArticleFile을 outer join을 이용하여 eager fetching하기 위한 맵핑은 아래와 같다.

<resultMap id="articleFilesResultMap" class="articleFile">
   <result property="fhandle" column="fhandle"/>
   <result property="articleId" column="articleFileArticleId"/>
   <result property="fileName" column="fileName"/>
   <result property="contentType" column="articleFileContentType"/>
   <result property="size" column="articleFileSize"/>
   <result property="regDate" column="articleFileRegDate"/>
</resultMap>

<resultMap id="latestArticleDetailMap" class="article" extends="articleResultMap" groupBy="id">
   <result property="articleContent.id" column="contentId" />
   <result property="articleContent.content" column="content" />
   <result property="commentCount" column="commentCount"/>
   <result property="articleFiles" resultMap="Article.articleFilesResultMap"/>
</resultMap>

<select id="getLatestArticles" parameterClass="map" resultMap="latestArticleDetailMap">
   SELECT
       a.*,
       ac.id contentId, ac.content,
       af.fhandle, af.articleId articleFileArticleId, af.fileName,
       af.contentType articleFileContentType, af.size articleFileSize,
       af.regDate articleFileRegDate,
       (SELECT COUNT(c.id) FROM articleA000001comment c WHERE c.articleId = a.id) commentCount
   FROM
       articleA000001 a , articleA000001content ac
   LEFT OUTER JOIN articleA000001file af ON af.articleId = a.id
   WHERE
       a.id = ac.id
   AND
       (status='S' OR status='L' OR deletedButDisplay=1)
   ORDER BY
       a.depth DESC
   LIMIT 0, 100
</select>


여기서 latestArticleDetailMap의 groupBy="id"가 키포인트이다.