Mybatis一对多与一对一

1. [代码]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>

2. [代码]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>