In-depth analysis of the working principle and process of MyBatis

Title: Detailed explanation of the working principle of MyBatis and process analysis

Introduction:
MyBatis is an excellent persistence layer framework that is widely used in Java projects. Understanding the working principle and process of MyBatis is very important for developers. This article will introduce the working principle of MyBatis in detail and explain its process through specific code examples.

1. Working Principle of MyBatis
The working principle of MyBatis can be summarized into the following key steps:

1. Parsing the configuration file
   The configuration file of MyBatis mainly contains database connections Information, SQL mapping configuration and global configuration, etc. At startup, MyBatis will parse these configuration files and generate corresponding data structures for subsequent operations.
2. Create SqlSessionFactory
   SqlSessionFactory is one of the core interfaces of MyBatis. It is responsible for creating SqlSession objects. SqlSession is the entrance to interact with the database. The creation of SqlSessionFactory depends on the configuration file and data source, through which you can obtain the database connection and execute the corresponding SQL statement.
3. Create SqlSession
   SqlSession is the core object for interacting with the database. It encapsulates the operation methods of the database, such as insert, update, delete and query. SqlSession is created through the openSession method of SqlSessionFactory, and each thread should have its own SqlSession object.
4. Perform SQL operations
   In the SqlSession object, you can perform SQL operations by calling the corresponding method. MyBatis supports multiple ways of SQL operations, such as executing SQL through mapping files, executing SQL through annotations, and constructing complex SQL statements through dynamic SQL.
5. Encapsulating result set
   After executing the SQL operation, MyBatis will encapsulate the result set returned by the database into a result set such as JavaBean, List or Map. This makes it easier for developers to process the returned results.
6. Submit transaction
   MyBatis enables transactions by default. When all SQL operations are completed, MyBatis will submit the transaction. If an exception occurs in the SQL operation, the transaction will be rolled back. Developers can also manually control the commit or rollback of transactions.
7. Close SqlSession
   When you do not need to use the SqlSession object, you need to explicitly close it. Closing the SqlSession will release the connection resources to the database and clear the first-level cache.

2. MyBatis process analysis
The following explains the workflow of MyBatis through specific code examples.

1. Configuration file example

   <configuration>
     <environments default="development">
    <environment id="development">
      <transactionManager type="JDBC"/>
      <dataSource type="POOLED">
        <property name="driver" value="${driver}"/>
        <property name="url" value="${url}"/>
        <property name="username" value="${username}"/>
        <property name="password" value="${password}"/>
      </dataSource>
    </environment>
     </environments>
     <mappers>
    <mapper resource="com/example/mapper/UserMapper.xml"/>
     </mappers>
   </configuration>

2. SqlSessionFactory creation example

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

3. SqlSession creation and SQL operation example

   SqlSession sqlSession = sqlSessionFactory.openSession();
   UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
   
   // 执行插入操作
   User user = new User();
   user.setUsername("test");
   user.setPassword("123456");
   userMapper.insert(user);
   
   // 执行查询操作
   User user = userMapper.selectById(1);
   System.out.println(user.getUsername());
   
   // 执行更新操作
   user.setUsername("updated");
   userMapper.update(user);
   
   // 执行删除操作
   userMapper.delete(user.getId());

4. Result set encapsulation example
   SQL mapping configuration in the UserMapper.xml file:

   <mapper namespace="com.example.mapper.UserMapper">
     <resultMap id="userResultMap" type="User">
    <id property="id" column="id"/>
    <result property="username" column="username"/>
    <result property="password" column="password"/>
     </resultMap>
     
     <select id="selectById" resultMap="userResultMap">
    SELECT * FROM user WHERE id = #{id}
     </select>
     
     <!-- 省略其他SQL配置 -->
   </mapper>

5. Example of committing transaction and closing SqlSession

   sqlSession.commit();
   sqlSession.close();

Conclusion:
It can be seen from the above analysis that the working principle and process of MyBatis are very clear. Developers only need to configure relevant information such as mapping files and data sources, that is, Simple code can be used to implement operations on the database. Mastering the working principles and processes of MyBatis is very helpful to improve development efficiency and write efficient database operations.

The above is the detailed content of In-depth analysis of the working principle and process of MyBatis. For more information, please follow other related articles on the PHP Chinese website!