MyBatis 延迟加载

在sqlMapConfig中进行设置

<configuration>
    <settings>
        <!--延迟加载的总开关-->
        <setting name="lazyLoadingEnabled" value="true"/>
        <!--设置为false才是启动延迟加载-->
        <setting name="aggresiveLazyLoading" value="false"/>
    </settings>
......
</configuration>

在mapper.xml中使用两次查询的方式；

 <!-- 2.查询两次select * from class where c_id = 1 ; SELECT * from teacher where 
        t_id = 1 -->

    <select id="getClass2" resultMap="getClass2Map">
        select * from class where c_id
        =#{id}
    </select>
    <select id="getTeacher" parameterType="int" resultType="com.stone.bean.Teacher">
        select
        t_id id,t_name name
        from teacher where t_id=#{id}
    </select>
    <select id="getStudents" parameterType="int" resultType="com.stone.bean.Student">
        select
        S_id id,s_name name from student where c_id=#{id}
    </select>
    <resultMap type="com.stone.bean.ClassT" id="getClass2Map">
        <id property="id" column="c_id" />
        <result property="name" column="c_name" />
        <association property="teacher" column="t_id" select="getTeacher">
        </association>
        <collection property="list" column="c_id" select="getStudents"></collection>
    </resultMap>