mybatis 一对一 一对多 （转）
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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