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  • mybatis 一对一 一对多

    一对一的XML配置文件

    <mapper namespace="dao.mapper.ClassMapper">

     <resultMap id="classResultMap" type="Classes">
      <id property="classid" column="classid1" />
      <result property="classname" column="classname" />
      <result property="teacherid" column="teacherid2" />
      <association property="teacher" column="teacherid" javaType="Teacher" select="getTeacher" />
    <!--   <association property="teacher" column="teacherid" javaType="Teacher" select="dao.mapper.TeacherMapper.getTeacher" />  两个XML文件之间调用 -->
     </resultMap>
     
     <select id="selectAllByClassId" parameterType="int" resultMap="classResultMap">
      select * from class c where c.classid = #{classid};
     </select>
     
     <select id="getTeacher" parameterType="int" resultType="teacher">
      select * from teacher tt where tt.teacherid = #{teacherid2}
     </select>
     
     
    </mapper>

    一对多 两个配置文件之间调用

    一对多中的"一"
    <mapper namespace="dao.mapper.ClassMapper">

     <resultMap id="classResultMap" type="Classes">
      <id property="classid" column="classid1" />
      <result property="classname" column="classname" />
      <result property="teacherid" column="teacherid2" />
      <collection property="studentList" column="classid" javaType="ArrayList" ofType="Student" select="StudentDao.getStudentByClassID" />
     </resultMap>
     
     <select id="selectAllByClassId" parameterType="int" resultMap="classResultMap">
      select * from class c where c.classid = #{classid};
     </select>
    </mapper>


    一对多中的"多"

    <mapper namespace="StudentDao">

     <resultMap type="Student" id="studentResultMap">
      <id property="studentid" column="studentid" />
      <result property="studentname" column="studentname" />
     </resultMap>
     
     <!-- 查询学生list,根据班级id -->
     <select id="getStudentByClassID" parameterType="String" resultMap="studentResultMap">
      select *from student st WHERE st.classid = #{classid1}
     </select>
    </mapper>

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  • 原文地址:https://www.cnblogs.com/lcuzhanglei/p/2513370.html
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