In-depth analysis of the functions and benefits of mybatis first-level cache

Analysis of the functions and advantages of MyBatis first-level cache

Introduction:
During the development process, database access operations are inevitable. In order to improve performance and reduce the number of database accesses, MyBatis provides a first-level cache mechanism. This article will explore the functions and advantages of MyBatis first-level cache, and illustrate it with specific code examples.

1. The role of the first-level cache

The first-level cache of MyBatis refers to the caching mechanism in the same SqlSession. The first-level cache is enabled by default and can improve query performance. The specific functions are as follows:

1. Reduce the number of database accesses: Using the first-level cache can avoid repeated queries to the database and improve system performance.
2. Improving response speed: Since the first-level cache is located in the memory, data is read faster, which can reduce network transmission time, thereby shortening response time.
3. Data consistency: In the same SqlSession, when multiple query operations operate on the same piece of data, MyBatis will automatically obtain data from the cache to ensure data consistency.

2. Advantages of first-level cache

MyBatis’s first-level cache has the following advantages:

1. Simple and easy to use: first-level cache Usage is transparent to developers, no manual operations are required, and data access operations can be performed directly.
2. Enabled by default: The first-level cache is enabled by default, that is, the execution results of SQL statements will be cached. In this way, you can directly obtain the benefits of caching without additional configuration.
3. Restricted scope: The scope of the first-level cache is limited to the same SqlSession. When the SqlSession is submitted or closed, the cache will be invalidated to avoid data inconsistency.

3. Code examples

The following uses specific code examples to demonstrate the use of first-level cache.

1. Create a UserMapper interface:

public interface UserMapper {
    User getUserById(int id);
    void updateUser(User user);
}

2. Enable first-level cache in the MyBatis configuration file:

<configuration>
    <!-- 其他配置 -->
    <settings>
        <setting name="cacheEnabled" value="true" />
    </settings>
    <!-- 其他配置 -->
</configuration>

3. Writing code example:

public static void main(String[] args) {
    try (SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(Resources.getResourceAsStream("mybatis-config.xml"))) {
        try (SqlSession sqlSession = sessionFactory.openSession()) {
            // 创建 UserMapper 的代理对象
            UserMapper userMapper = sqlSession.getMapper(UserMapper.class);

            // 第一次查询，会从数据库中获取数据，并将数据缓存到一级缓存中
            User user1 = userMapper.getUserById(1);
            System.out.println(user1);

            // 第二次查询，会从一级缓存中获取数据，不会访问数据库
            User user2 = userMapper.getUserById(1);
            System.out.println(user2);
            
            // 更新用户信息
            user1.setName("New Name");
            userMapper.updateUser(user1);

            // 清除一级缓存
            sqlSession.clearCache();

            // 第三次查询，会从数据库中获取数据，并将新的数据缓存到一级缓存中
            User user3 = userMapper.getUserById(1);
            System.out.println(user3);
        }
    }
}

In the above example, the first query will get the data from the database and cache it into the first level cache. During the second query, the data is obtained directly from the first-level cache, avoiding the need to access the database again. After the user information is updated, the first-level cache is cleared, and the third query will re-obtain the latest data from the database and cache it in the first-level cache.

In summary, MyBatis's first-level cache has obvious advantages in improving database access performance and reducing network transmission delays. Developers only need simple configuration to enjoy the convenience brought by the first-level cache.

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