Mybatis多表关联查询字段值覆盖问题

时间：2022-12-29 15:09:54

错误展示

  • 多表关联查询的返回结果集
	<resultMap id="specialdayAndWorktimeMap type="com.hierway.resm.domain.manage.timeSchedule.SpecialDayWorkTimeVO">

  		<id column="special_date_id" property="specialDateId"/>

 		<result column="name" property="name"/>

  		<result column="date" property="date"/>

  		<result column="type" property="type"/>

  		<result column="start_time" property="startTime"/>

  		<result column="end_time" property="endTime"/>

  		<collection property="workTimeList" ofType="com.hierway.resm.domain.manage.timeSchedule.WorkTime">

    		<id column="work_time_id" property="workTimeId"/>

    		<result column="start_time" property="startTime"/>

   			<result column="end_time" property="endTime"/>

  		</collection>

	</resultMap>

上面的映射中，返回结果类：SpecialDayWorkTimeVO中定义了7个属性，其中第7个属性是关联查询一对多的对象List。

可以看到在workTime中的属性startTime与endTime和上面的startTime与endTime属性名相同。

  • 查询语句展示
	<select id="getSpecialDayAndWorkTimesByPuId" resultMap="specialdayAndWorktimeMap">

	  SELECT sd.special_date_id,sd.name,sd.type,sd.date,sd.start_time,sd.end_time,wt.work_time_id,wt.start_time,wt.end_time

	 FROM powerunit_specialday_relation AS psr

	  LEFT JOIN special_day AS sd ON psr.special_date_id = sd.special_date_id

	 LEFT JOIN specailday_worktime_relation AS swr ON sd.special_date_id = swr.special_date_id

	 LEFT JOIN work_time AS wt ON swr.work_time_id = wt.work_time_id

	 WHERE psr.pu_id = #{puId}

	</select>

在junit中进行mapper层测试，原本数据库中只有一条SpecialDay的记录，并没有关联的WorkTime记录，那么理想的结果是返回的VO对象中

specialDay相关的属性有值，而List是一个长度为0的List。可是测试结果转为Json格式如下所示：

[{"specialDateId":2,"name":"b","date":"2019-04-27","type":0,"startTime":"5:00","endTime":"17:00","workTimeList":[{"workTimeId":null,"startTime":"5:00","endTime":"17:00"}]}]

可以看到，list中含有一条数据，且前面的属性，覆盖了后面具有相同属性名的WorkTime中的startTime与endTime值，结果与测试结果不符合。

解决方案

  • 给workTime表查询结果设置一个区分的别名，同时修改resultMap中标签下的对应的字段名（column元素），展示如下：
	<resultMap id="specialdayAndWorktimeMap" type="com.hierway.resm.domain.manage.timeSchedule.SpecialDayWorkTimeVO">

	    <id column="special_date_id" property="specialDateId"/>

	    <result column="name" property="name"/>

	    <result column="date" property="date"/>

	    <result column="type" property="type"/>

	    <result column="start_time" property="startTime"/>

	    <result column="end_time" property="endTime"/>

	    <collection property="workTimeList" ofType="com.hierway.resm.domain.manage.timeSchedule.WorkTime">

	      <id column="work_time_id" property="workTimeId"/>

	      <result column="wstart_time" property="startTime"/>

	      <result column="wend_time" property="endTime"/>

	    </collection>

	  </resultMap>  

	 <!--List<SpecialDayWorkTimeVO> getSpecialDayAndWorkTimesByPuId(Integer puId);-->

	 <select id="getSpecialDayAndWorkTimesByPuId" resultMap="specialdayAndWorktimeMap">

	    SELECT sd.special_date_id,sd.name,sd.type,sd.date,sd.start_time,sd.end_time,wt.work_time_id,wt.start_time AS wstart_time ,wt.end_time AS wend_time

	    FROM powerunit_specialday_relation AS psr

	    LEFT JOIN special_day AS sd ON psr.special_date_id = sd.special_date_id

	 LEFT JOIN specailday_worktime_relation AS swr ON sd.special_date_id = swr.special_date_id

	 LEFT JOIN work_time AS wt ON swr.work_time_id = wt.work_time_id

	 WHERE psr.pu_id = #{puId}

	</select>
  • 相同测试数据如下：
[{"specialDateId":2,"name":"b","date":"2019-04-27","type":0,"startTime":"5:00","endTime":"17:00","workTimeList":[]}]

此次测试结果正确！workTimeList长度为0。

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