mybatis关联映射

<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
<mapper>
<resultMap id="studentResultMap" type="com.demo.domain.Student">
<id property="id" column="id"/>
<result property="name" column="name"/>
<result property="sex" column="sex"/>
<result property="age" column="age"/>

<!--关联映射：一个学生关联一个班级-->
<association property="clazz" column="clazz_id" javaType="com.demo.domain.Clazz" select="selectClazzWithId"/>
</resultMap>

<!--查询关联班级-->
<select id="selectClazzWithId" resultType="com.demo.domain.Clazz">
SELECT * FROM TB_CLAZZ WHERE id = #{id}
</select>

<!--查询学生-->
<select id="selectStudent" resultMap="studentResultMap">
SELECT * FROM TB_STUDENT
</select>
</mapper>

<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
<mapper>
<resultMap id="clazzResultMap" type="com.demo.domain.Clazz">
<id property="id" column="id"/>
<result property="code" column="code"/>

<!--关联映射：一个班级有多个学生，返回一个List集合-->
<collection property="students" javaType="ArrayList" column="id" ofType="com.demo.domain.Student" select="selectStudentWithId"/>
</resultMap>

<!--查询关联的学生-->
<select id="selectStudentWithId" resultType="com.demo.domain.Student">
SELECT * FROM TB_STUDENT WHERE clazz_id = #{id}
</select>

<!--查询班级-->
<select id="selectClazz" resultMap="clazzResultMap">
SELECT * FROM TB_CLAZZ
</select>
</mapper>