mybatis resultMap之collection聚集两种实现方式

<collection property="Java属性名" ofType="另一Java类名" javaType="ArrayList" column="关联主键ID(用于嵌套查询SQL语句传入参数，多个用逗号分开)" select="另一个select映射SQL的ID"/>

<select parameterType="int" resultType="另一Java类名" id="另一个select映射SQL的ID">
	SQL语句
</select>

<resultMap id="blogResult" type="Blog">  
	<collection property="posts" javaType=”ArrayList” column="blog_id" ofType="Post" select="selectPostsForBlog"/>  
</resultMap>  
   
<select id="selectBlog" parameterType="int" resultMap="blogResult">  
	SELECT * FROM BLOG WHERE ID = #{id}  
</select>  
   
<select id="selectPostsForBlog" parameterType="int" resultType="Author">  
	SELECT * FROM POST WHERE BLOG_ID = #{id}  
</select>

<resultMap id="resultMap的ID"  type="Java类名">
	<collection property="Java属性名" ofType="另一Java类名" javaType="ArrayList" resultMap="另一resultMap的ID"/>
</resultMap>
  
<resultMap="另一resultMap的ID" type="另一Java类名">
	<id property="id" column="关联主键ID"/>
	....
</resultMap>

<select id="selectBlog" parameterType="int" resultMap="blogResult">  
	select  
		B.id as blog_id,  
		B.title as blog_title,  
		B.author_id as blog_author_id,  
		P.id as post_id,  
		P.subject as post_subject,  
		P.body as post_body,  
	from Blog B  
	left outer join Post P on B.id = P.blog_id  
	where B.id = #{id}  
</select>

<resultMap id="blogResult" type="Blog">  
	<id property="id" column="blog_id" />  
	<result property="title" column="blog_title"/>  
	<collection property="posts" ofType="Post">  
		<id property="id" column="post_id"/>  
		<result property="subject" column="post_subject"/>  
		<result property="body" column="post_body"/>  
	</collection>  
</resultMap>  

<resultMap id="blogResult" type="Blog">  
	<id property="id" column="blog_id" />  
	<result property="title" column="blog_title"/>  
	<collection property="posts" ofType="Post" resultMap="blogPostResult"/>  
</resultMap>  
   
<resultMap id="blogPostResult" type="Post">  
	<id property="id" column="post_id"/>  
	<result property="subject" column="post_subject"/>  
	<result property="body" column="post_body"/>  
</resultMap>