Deep Dive into MyBatis: Architecture, Configuration Parsing, Proxy Creation, and SQL Execution

The article introduces MyBatis as a lightweight, stable ORM framework for Java that maps objects to relational databases, highlighting its main capabilities such as SQL mapping configuration, dynamic SQL, parameter mapping, result set mapping, transaction management, connection‑pool integration, and second‑level caching.

It explains that MyBatis’s architecture consists of three layers—foundation support, core processing, and interface layer—and outlines the overall workflow: defining interfaces and XML/annotation configurations, loading and parsing configuration files, generating mapper proxies via SqlSession.getMapper, and finally executing SQL.

During configuration parsing, MyBatis loads the main mybatis-config.xml file into a Configuration object, uses XMLConfigBuilder for global settings, XMLMapperBuilder for mapper files, and XMLStatementBuilder for individual SQL statements.

Proxy construction involves MapperProxyFactory, MapperRegistry, and MapperProxy, leveraging JDK dynamic proxies to create concrete implementations of mapper interfaces.

The SQL execution phase relies on standard JDBC operations: creating Statement / PreparedStatement / CallableStatement, executing queries, handling ResultSet, and mapping results back to Java objects. MyBatis supports various execution methods such as selectOne(), selectList(), insert(), update(), and delete().

Key code example for initializing MyBatis:

// <1> Load configuration file
 InputStream is = Resources.getResourceAsStream("mybatis.xml");
 // <2> Build SqlSessionFactory
 sessionFactory = new SqlSessionFactoryBuilder().build(is);
 // <3> Open SqlSession
 SqlSession session = factory.openSqlSession();
 // <4> Get mapper proxy
 UserMapper mapper = session.getMapper(UserMapper.class);
 // ... invoke mapper methods

Finally, the article summarizes the complete MyBatis workflow: creating a SqlSessionFactory, opening a SqlSession, executing SQL via mapper methods, parsing SQL (including dynamic SQL and parameter/result mapping), sending the statement to the database, and mapping the results back to Java objects.