在mybatis-config.xml中开启延迟加载：开启懒加载、延迟加载没有效果解决；

冷不防 2022-04-18 02:08 338阅读 0赞

***声明使用JDK8测试；***

*参考官网配置，网址如下：*  
[http://www.mybatis.org/mybatis-3/zh/configuration.html][http_www.mybatis.org_mybatis-3_zh_configuration.html]

![如下][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjMyMzgwMg_size_16_color_FFFFFF_t_70]  
aggressiveLazyLoading 在mybatis版本小于3.4.1时候，默认是true开启状态，懒加载要有效果需要手动关闭；  
①在mybatis-config.xml中 手动开启lazyLoadingEnabled ；  
②在mybatis-config.xml中 手动关闭aggressiveLazyLoading；

*或者使用最新 mybatis版本 mybatis3.4.7*

*运行下懒加载有效果：使用到 user对象时候加载 sql*  
![sd][]  
*放开注释再跑一下；*  
![瞅瞅][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjMyMzgwMg_size_16_color_FFFFFF_t_70 1]

*mapper.xml配置；*

<select id="findOrderByNumberLazy" resultMap="orderUserMapLazy">
              SELECT * FROM tb_order where order_number = #{number}
        </select>
        <resultMap id="orderUserMapLazy" type="Order" autoMapping="true">
            <id column="id" property="id"/>
            <association property="user" javaType="User" select="queryUser" column="user_id">
            </association>
        </resultMap>
        <select id="queryUser" resultType="User">
            SELECT  * from tb_user where id = #{user_id}
        </select>

*UserMapper接口；*

/** * 一对一延迟加载 */
         Order findOrderByNumberLazy(@Param("number")String number);

*单元测试；*

/** * 一对一懒加载 */
        @Test
        public void test12() { 
            Order order = mapper.findOrderByNumberLazy("20140921002");
            System.out.println(order.getOrderNumber());
            System.out.println("===========");
            System.out.println(order.getUser());
    
        }

![sdf][]

[http_www.mybatis.org_mybatis-3_zh_configuration.html]: http://www.mybatis.org/mybatis-3/zh/configuration.html
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjMyMzgwMg_size_16_color_FFFFFF_t_70]: /images/20220418/3ca19579ca794617afb7f513f9338edc.png
[sd]: /images/20220418/fd00bff22c2a436981e6e85e7b3f911d.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjMyMzgwMg_size_16_color_FFFFFF_t_70 1]: /images/20220418/eb005dc8f2054877b29150115859f853.png
[sdf]: /images/20220418/0487caade87e4295a3819ca778464dff.png