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:
2. Advantages of first-level cache
MyBatis’s first-level cache has the following advantages:
3. Code examples
The following uses specific code examples to demonstrate the use of first-level cache.
public interface UserMapper { User getUserById(int id); void updateUser(User user); }
<configuration> <!-- 其他配置 --> <settings> <setting name="cacheEnabled" value="true" /> </settings> <!-- 其他配置 --> </configuration>
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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