iBATIS 3 试用手记二
? 接昨晚的继续，今天仔细研究了下<association>和<collection>标签，对于它们的写法比较灵活，在这儿我列举三种<resultMap>的写法，它们最终的查询结果都是一致的。
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第一种：Nested(内联)写法
请参看我上篇文章，在此不详述了。
第二种：将Nested的resultMap单独定义，使用<association>和<collection>的resultMap属性指定，同时查询的SQL与第一种方式相同，需要Join相关联的表。代码如下：
resultMap="resultMap-content" /><collection property="newsNoticeMsgBoxList" ofType="org.newsnotice.domain.NewsNoticeMsgBoxModel" resultMap="resultMap-msgbox" /></resultMap><resultMap type="org.newsnotice.domain.NewsNoticeContentModel" id="resultMap-content"><id column="CONTENT_ID" property="contentId" /><result column="PARENT_NN_ID" property="parentId" /><result column="CONTENT" property="content" /></resultMap><resultMap type="org.newsnotice.domain.NewsNoticeMsgBoxModel" id="resultMap-msgbox"><id column="MSG_BOX_ID" property="msgBoxId"/><result column="USER_ID" property="userId" /><result column="MSG_BOX_NN_ID" property="nnId" /><result column="FOLDER" property="folder" /><result column="READ" property="read" /><result column="READ_ON" property="readOn" /><result column="MSG_BOX_DEFUNCT_IND" property="defunctInd" /><result column="MSG_BOX_PI_NO" property="piNo" /></resultMap><select id="getNewsNotice2" parameterType="org.newsnotice.domain.NewsNoticeModel" resultMap="resultMap-getNewsNotice2" >SELECT A.NN_ID, A.CATEGORY, A.SUBJECT, A.POSTED_DATE, A.EXPIRY_DATE, A.ALERT, A.EMAIL_ALERT, A.AUDIENCE,A.FILTER, A.FILTER_VALUE, A.SUB_FILTER_VALUE, A.EXCLUDE_USER_ID, A.WF_DEPARTMENT, A.WF_STATUS, A.WF_NOTES,A.DEFUNCT_IND, A.APPROVER, B.ID CONTENT_ID, B.PARENT_NN_ID, B.CONTENT, C.ID MSG_BOX_ID, C.USER_ID, C.NN_ID MSG_BOX_NN_ID, C.FOLDER, C.READ, C.READ_ON, C.DEFUNCT_IND MSG_BOX_DEFUNCT_IND, C.PI_NO MSG_BOX_PI_NOFROM NN_MSTR A, NN_CONTENT B, NN_MSG_BOX CWHERE A.NN_ID = B.PARENT_NN_IDAND A.NN_ID = C.NN_ID<if test="nnId != null">AND A.NN_ID = #{nnId}</if><if test="category != null">AND A.CATEGORY = #{category}</if><if test="status != null">AND A.WF_STATUS = #{status}</if></select><!-- End. -->?
第三种方式：使用独立的select查询来获取数据，并通过<association>和<collection>的select属性来指定。这种方式需要注意的是主表查询是针对单表，并不join相关联的其它表；同时用column属性指定要传入select指定独立查询中的参数值。代码如下：
column="PARENT_NN_ID" javaType="org.newsnotice.domain.NewsNoticeContentModel" select="selectContent"/><collection property="newsNoticeMsgBoxList" ofType="org.newsnotice.domain.NewsNoticeMsgBoxModel" select="selectMsgBox" column="MSG_BOX_NN_ID"/></resultMap><!-- 注意此处的查询为单表查询，并未join相关联的表 --><select id="getNewsNotice3" parameterType="org.newsnotice.domain.NewsNoticeModel" resultMap="resultMap-getNewsNotice3">SELECT A.NN_ID, A.CATEGORY, A.SUBJECT, A.POSTED_DATE, A.EXPIRY_DATE, A.ALERT, A.EMAIL_ALERT, A.AUDIENCE,A.FILTER, A.FILTER_VALUE, A.SUB_FILTER_VALUE, A.EXCLUDE_USER_ID, A.WF_DEPARTMENT, A.WF_STATUS, A.WF_NOTES,A.DEFUNCT_IND, A.APPROVER, A.NN_ID PARENT_NN_ID, A.NN_ID MSG_BOX_NN_IDFROM NN_MSTR A<where><if test="nnId != null">AND A.NN_ID = #{nnId}</if><if test="category != null">AND A.CATEGORY = #{category}</if><if test="status != null">AND A.WF_STATUS = #{status}</if></where></select><!-- 此处的参数接收由主查询传入的值，至于属性名可以随便写，如此处的xxxxx,yyyyy --><select id="selectContent" parameterType="int" resultMap="resultMap-content">SELECT B.ID CONTENT_ID, B.PARENT_NN_ID, B.CONTENT FROM NN_CONTENT BWHERE B.PARENT_NN_ID = #{xxxxxx}</select><select id="selectMsgBox" parameterType="int" resultMap="resultMap-msgbox">SELECT C.ID MSG_BOX_ID, C.USER_ID, C.NN_ID MSG_BOX_NN_ID, C.FOLDER, C.READ, C.READ_ON, C.DEFUNCT_IND MSG_BOX_DEFUNCT_IND, C.PI_NO MSG_BOX_PI_NOFROM NN_MSG_BOX CWHERE C.NN_ID = #{yyyyyy}</select><!-- End. -->?
在这儿还是给出代码中涉及到的三个domain对象代码，方便大家对应看。
public class NewsNoticeContentModel {private long contentId;private long parentId;private byte[] content;......//省略get/set方法?
哦，对了，忘记说了，源代码可以直接用eclipse导入，JUnit测试类在org.ibatis3.test包下。
1 楼 alex_chew 2010-01-18 压缩包里没有建表SQL，能否补充Mysql的建表语句 2 楼 cfanboy 2010-02-01 不好意思，这些例子我是使用的公司项目数据库，由于涉及保密及安全性故不能给出SQL