Mybatis 中的 xml 配置问题

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    <resultMap id="historyResultMap" type="org.hugcode.common.pojo.User">
        <id column="uid" property="uid"/>
        <result column="username" property="username"/>
        <result column="password" property="password"/>
        <result column="updated" property="updated"/>
        <result column="created" property="created"/>

        <collection property="userHistories" ofType="org.hugcode.common.pojo.UserHistory">
            <result column="correct" property="correct"/>
            <result column="reply" property="reply"/>
            <result column="created" property="created"/>
            <result column="updated" property="updated"/>
            <association property="question" javaType="org.hugcode.common.pojo.Question">
                <!--   这一块出错了-->
                <id column="qid" property="qid"/>
                <result column="description" property="description"/>
                <result column="answer" property="answer"/>
                <result column="type" property="type"/>
            </association>
        </collection>
    </resultMap>

万能的 v 友们，很奇怪 idea 报了错 property (qid) can not found setter method ，但实际能正常运行，但结果存在问题：sql 语句查询后有八行，但 mybatis 返回的只有五行（数据库中并未存在 null 值）

4 replies

PeanutMi

Nov 22, 2023

<resultMap id="questionResultMap" type="org.hugcode.common.pojo.User">
<id column="uid" property="uid"/>
<result column="username" property="username"/>
<result column="password" property="password"/>
<result column="updated" property="updated"/>
<result column="created" property="created"/>
<collection property="questions" ofType="org.hugcode.common.pojo.Question">
<id column="qid" property="qid"/>
<result column="description" property="description"/>
<result column="answer" property="answer"/>
<result column="type" property="type"/>
</collection>

</resultMap>
<select id="findQuestionsByUid" resultMap="questionResultMap">
SELECT question.*,user.* FROM question,user,user_history WHERE user.uid = #{uid} AND user_history.uid = user.uid AND user_history.qid = question.qid
</select>

单纯在 User 类中一对多是没有问题的，但我想在关系表 user_history 保存用户的做题记录所以想新弄个实体类 UserHistory 存其他信息，结果就出现问题了😭，下面是包含关系
（ 1 ）正确：User ->List<Question>（ collection ）
（ 2 ）错误：User ->List<UserHistory> （ collection ）->Question （ association ）

PeanutMi

Nov 22, 2023

主题中的查询语句
<select id="findQuestionsByUid" resultMap="questionResultMap">
SELECT question.*, user.*, user_history.reply,user_history.h_updated,user_history.h_created,user_history.correct
FROM question,
user,
user_history
WHERE user.uid = #{uid}
AND user_history.uid = user.uid
AND user_history.qid = question.qid
</select>

PeanutMi

Nov 22, 2023

@gomorebug id 搞错了，是这个
<select id="findHistoryByUid" resultMap="historyResultMap">
SELECT question.*, user.*, user_history.reply,user_history.h_updated,user_history.h_created,user_history.correct
FROM question,
user,
user_history
WHERE user.uid = #{uid}
AND user_history.uid = user.uid
AND user_history.qid = question.qid
</select>

PeanutMi

Nov 22, 2023

@gomorebug 解决了，在 UserHistory 添加成员变量 qid 和 uid ，在映射中也添加