Decrypting the MyBatis caching mechanism: the key to improving application efficiency

MyBatis caching mechanism analysis: the secret to improving application efficiency

Cache is one of the important means to improve application performance, and when using a persistence layer framework like MyBatis When doing so, a full understanding of its caching mechanism will help optimize program performance. This article will provide an in-depth analysis of the caching mechanism of MyBatis and provide specific code examples so that readers can better understand how to use caching to improve the efficiency of applications.

1. Overview of MyBatis caching mechanism

The caching mechanism of MyBatis is mainly divided into two types: first-level cache and second-level cache. The first-level cache is a SqlSession-level cache, and cached data between different SqlSession is not shared; while the second-level cache is a Mapper-level cache, and data can be shared across SqlSession. Proper use of cache can reduce the number of database accesses, thereby improving program performance.

2. First-level cache example

The first-level cache is enabled by default and cannot be turned off. It is only valid in the same SqlSession. When querying the same data, MyBatis will first query from the cache, and if there is a miss, it will send SQL to the database for query. The following is a simple example:

SqlSession sqlSession = sqlSessionFactory.openSession();
UserMapper userMapper = sqlSession.getMapper(UserMapper.class);

// 第一次查询
User user1 = userMapper.selectUserById(1);
// 第二次查询，应该从缓存中获取，而不是发送SQL查询
User user2 = userMapper.selectUserById(1);

sqlSession.close();

3. Second-level cache example

The second-level cache needs to be manually configured and used. Add the following configuration in mapper.xml:

<cache/>

Below This is a simple second-level cache example:

SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
SqlSession sqlSession1 = sqlSessionFactory.openSession();
UserMapper userMapper1 = sqlSession1.getMapper(UserMapper.class);

// 第一次查询，发送SQL至数据库查询
User user1 = userMapper1.selectUserById(1);

// 提交事务，将数据写入到二级缓存中
sqlSession1.commit();
sqlSession1.close();

SqlSession sqlSession2 = sqlSessionFactory.openSession();
UserMapper userMapper2 = sqlSession2.getMapper(UserMapper.class);

// 第二次查询相同数据，应该直接从二级缓存中获取，而不是发送SQL查询
User user2 = userMapper2.selectUserById(1);

sqlSession2.close();

4. Cache invalidation and refresh

During the running of the application, the cache may become invalid or need to be refreshed manually. MyBatis provides the clearCache() method for manually refreshing the cache. At the same time, you can add the @Options annotation to the method of the Mapper interface to set the cache invalidation policy.

Conclusion

By rationally using MyBatis’ caching mechanism, we can effectively improve the performance of the application. In actual projects, selecting the appropriate cache level and configuration options according to the actual situation, and tuning based on specific business needs will achieve significant results.

I hope this article can help readers better understand the caching mechanism of MyBatis and deepen their impression through code examples. In actual application development, rational use of the cache mechanism will be one of the important means to improve program performance.

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