ibatis2.3中groupBy 一对多 解决N+1问题过程中遇到的问题..

刚学ibatis,参考网上的例子写了个一对多的小例子,用groupBy+关联查询可以只查询一次就能取出符合条件的UserList,同时每个User对象中,都还插入了UserScoreList.

刚开始是这么写的配置文件:

<resultMap class="User" id="_u" groupBy="id">
    <result property="id" column="ID" />
    <result property="name" column="NAME" />
    <result property="gender" column="GENDER" />
    <result property="age" column="AGE" />
    <result property="userScoreList" resultMap="userDetail._us" /><!--对应user中的userScoreList列表-->
</resultMap>

<resultMap class="UserScore" id="_us">
    <result property="scoreId" column="ID" />
    <result property="userId" column="USER_ID" />
    <result property="scoreName" column="SCORE_NAME" />
　　 <result property="totalScore" column="TOTAL_SCORE" />
    <result property="objectiveScore" column="OBJECTIVE_SCORE" />
    <result property="subjectiveScore" column="SUBJECTIVE_SCORE" />
</resultMap>

<select id="findUserByUsName" parameterClass="java.util.Map" resultMap="userDetail._u" >
        select u.ID                as id,
               u.NAME　　　　　　　  as name,
               u.GENDER            as gender,
               u.AGE               as age,
               us.ID               as scoreId,
               us.USER_ID          as userId,
               us.NAME             as scoreName,
               us.TOTAL_SCORE      as totalScore,
               us.OBJECTIVE_SCORE  as objectiveScore,
               us.SUBJECTIVE_SCORE as subjectiveScore
          from MQ_TEST_USER u
          left join MQ_TEST_USER_SCORE us
          on   u.ID = us.USER_ID
         where us.NAME in
                  <iterate property="subjects" open="(" close=")" conjunction=",">
                #subjects[]#
                </iterate>
</select>

执行之后总是报 列名无效....纠结了很久,,,突然想到as就是起别名,然后在resultMap中的column属性应该与结果集相对应,所以如果起了别名,反而会和column属性冲突..遂改之..结果不报错了,然后发现userScoreList中的数据是不对的,name的值居然是user中name的值.因为没有起别名,结果集中u.ID和us.ID还有name列名相同了,导致userScore对象插入的是user中对应的id和name..遂又改之..终于对了....

正确配置如下:

    <resultMap class="User" id="_u" groupBy="id">
        <result property="id" column="ID" />
        <result property="name" column="NAME" />
        <result property="gender" column="GENDER" />
        <result property="age" column="AGE" />
        <result property="userScoreList" resultMap="userDetail._us" />
    </resultMap>

    <resultMap class="UserScore" id="_us">
        <result property="scoreId" column="scoreId" />
        <result property="userId" column="USER_ID" />
        <result property="scoreName" column="scoreName" />
        <result property="totalScore" column="TOTAL_SCORE" />
        <result property="objectiveScore" column="OBJECTIVE_SCORE" />
        <result property="subjectiveScore" column="SUBJECTIVE_SCORE" />
    </resultMap>
    <select id="findUserByUsName" parameterClass="java.util.Map" resultMap="userDetail._u" >
        select u.ID,
               u.NAME,
               u.GENDER,
               u.AGE,
               us.ID             as scoreId,　　　　　　　　　　//将id和name于user中的分开,然后在resultMap中配置对应的column属性.
               us.USER_ID,
               us.NAME           as scoreName,
               us.TOTAL_SCORE,
               us.OBJECTIVE_SCORE,
               us.SUBJECTIVE_SCORE
          from      MQ_TEST_USER u
          left join MQ_TEST_USER_SCORE us
          on        u.ID = us.USER_ID
          where us.NAME in
                  <iterate property="subjects" open="(" close=")" conjunction=",">
                    #subjects[]#
                </iterate>
    </select>