Analysis of MyBatis caching mechanism: optimizing data query and reading speed

(This article will discuss the caching mechanism in the MyBatis framework, aiming to speed up data query and reading. The article will expand on the role, type, configuration and specific code examples of the MyBatis cache. Discussion to help readers deeply understand and use the caching mechanism of MyBatis.)

When using MyBatis for database operations, in order to improve query efficiency and reduce database access pressure, we usually use the caching mechanism to cache query results. The MyBatis framework provides a variety of cache types and configuration options. Properly configuring the cache can effectively speed up the data query and reading process.

1. The role of MyBatis cache

The main role of MyBatis cache is to avoid frequent queries to the database. By caching query results, you can reduce the number of database accesses and improve system performance. and response speed. When an application requires the same query results, it can fetch the data directly from the cache without sending a query request to the database each time.

2. Types of MyBatis cache

MyBatis framework provides two cache types: first-level cache (Local Cache) and second-level cache (Global Cache).

1. Level 1 cache (Local Cache): Level 1 cache is a SqlSession-level cache. When the SqlSession object executes a query, the query results will be cached inside the SqlSession object. When the same SqlSession object executes the same query, data can be obtained directly from the first-level cache.
2. Second-level cache (Global Cache): The second-level cache is a Mapper-level cache. Multiple SqlSession objects can share the same Mapper's second-level cache. When different SqlSession objects execute the same query, data can be obtained from the second-level cache to avoid repeated queries.

3. MyBatis cache configuration

The cache can be configured in the MyBatis configuration file, including enabling cache, setting cache type, invalidation policy, etc. . The following is a simple MyBatis configuration file example for configuring the second-level cache:

<configuration>
    <settings>
        <setting name="cacheEnabled" value="true"/>
    </settings>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="com/example/mapper/UserMapper.xml"/>
    </mappers>
</configuration>

In the above configuration file, we set <setting name="cacheEnabled" value="true"></setting>The cache is enabled, and the data source and Mapper mapping files are configured.

4. MyBatis cache code example

The following is a simple MyBatis code example that demonstrates how to use the first-level cache and the second-level cache:

// 创建SqlSessionFactory对象
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

// 创建SqlSession对象
SqlSession sqlSession = sqlSessionFactory.openSession();

// 使用一级缓存（Local Cache）
UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
User user1 = userMapper.selectUserById(1);
User user2 = userMapper.selectUserById(1); // 第二次查询直接从一级缓存中获取数据

// 使用二级缓存（Global Cache）
SqlSession sqlSession2 = sqlSessionFactory.openSession();
UserMapper userMapper2 = sqlSession2.getMapper(UserMapper.class);
User user3 = userMapper2.selectUserById(1); // 从二级缓存中获取数据

// 提交事务并关闭资源
sqlSession.commit();
sqlSession.close();
sqlSession2.commit();
sqlSession2.close();

In the above code, we obtain the instance of the UserMapper interface through sqlSession.getMapper(UserMapper.class), and then demonstrate the use of the first-level cache and the second-level cache .

Through the introduction of this article, we understand the role, type, configuration and code examples of cache in the MyBatis framework. Properly configuring the cache can significantly improve the efficiency of data query and reading, which is of great significance for improving system performance and response speed. I hope this article can help readers gain a deeper understanding and application of MyBatis' caching mechanism.

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