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>