Mybatis工作原理及缓存

た入场券 2023-05-30 06:00 68阅读 0赞

### Mybatis工作原理 ###

简单一句话总结：

SqlSession根据statementID，在Mybatis的配置对象Configuration中获取到对应的
    MapperStatement对象，然后调用Mybatis执行器来执行具体的操作

流程图如下：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L21hbWVuZzE5ODg_size_16_color_FFFFFF_t_70]  
测试：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L21hbWVuZzE5ODg_size_16_color_FFFFFF_t_70 1]![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L21hbWVuZzE5ODg_size_16_color_FFFFFF_t_70 2]

### Mybatis一级缓存 ###

#### 一级缓存命中原则 ####

*  stattis工作原理  
    简单一句话总结：`yamlSqlSession根据statementID，在Mybatis的配置对象Configuration中获取到对应的MapperStatement对象，然后调用Mybatis执行器来执行具体的操作`流程图如下：![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L21hbWVuZzE5ODg_size_16_color_FFFFFF_t_70]测试：![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L21hbWVuZzE5ODg_size_16_color_FFFFFF_t_70 1]![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L21hbWVuZzE5ODg_size_16_color_FFFFFF_t_70 2]

### Mybatis一级缓存 ###

#### 一级缓存命中原则 ####

即：Mybatis是如何判断某两次查询是完全相同的查询？

*  statementId需相同
 *  传给sql语句的参数（包含分页参数）需相同
 *  sql语句需相同
 *  环境需相同

#### 一级缓存生命周期 ####

由于关闭Session、执行Commit、执行Rollback都会清空Mybatis一级缓存，所以实际上：  
Mybatis一级缓存的生命周期是在数据库事务的生命周期之内的

*  缓存的产生：  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L21hbWVuZzE5ODg_size_16_color_FFFFFF_t_70 3]
 *  缓存的销毁：

1、sqlSession的关闭
    2、sqlSession的commit
    3、sqlSession的rollback
    4、执行insert、update、delete操作，会清空所有的缓存（与表无关）
    5、sqlSession的clearCache()

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L21hbWVuZzE5ODg_size_16_color_FFFFFF_t_70 4]

#### Mybatis如何解决数据库事务问题 ####

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L21hbWVuZzE5ODg_size_16_color_FFFFFF_t_70 5]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L21hbWVuZzE5ODg_size_16_color_FFFFFF_t_70 6]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L21hbWVuZzE5ODg_size_16_color_FFFFFF_t_70 7]

参考：1、[Mybatis的工作原理，你了解过吗？][Mybatis]  
2、[mybatis工作原理][mybatis]

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![在这里插入图片描述][2019121114401180.png]

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[Mybatis]: https://mp.weixin.qq.com/s?__biz=MzAxNjk4ODE4OQ==&mid=2247487259&idx=1&sn=04528a11bf2e8e59e667cfceb1ac79ed&chksm=9bed2e69ac9aa77fa04c11a423466cb298b81b1f851f275418ab521708cae89308065e3ce90c&mpshare=1&scene=1&srcid=&sharer_sharetime=1573093353466&sharer_shareid=2312c9731de66c3a71ee53f2245ca3da&key=545408ebeb53b5258fc0e1e5d379a69f1f518d242aa876994ddcacbe9c9adbd3c085a33ba2ea88c6927c62ebe0c4563ac10203063430401e0d3f57e49e7e96c45d08dc821f4be858179a6387d963d166&ascene=1&uin=MzQ3ODIzNzgzNA==&devicetype=Windows%2010&version=62070152&lang=zh_CN&pass_ticket=uGfiDWjkQDvHQePRqqM7KB5fQHium/hSYyltgKtRn1l8lONgzN2lOLgjn%2bL18leh
[mybatis]: https://blog.csdn.net/xl_1803/article/details/82492499
[2019121114401180.png]: https://img-blog.csdnimg.cn/2019121114401180.png