Understanding MyBatis: A Complete Architecture Overview and Workflow

1. Introduction

MyBatis is an ORM framework that maps Java objects to relational databases, valued for its lightweight nature, stability, and active open‑source community.

MyBatis provides several key capabilities:

SQL mapping configuration : uses XML or annotations to define SQL statements and their mapping to tables, separating SQL from Java code.

Dynamic SQL : supports conditional generation of SQL statements.

Parameter mapping : automatically maps Java object properties to SQL parameters.

Result mapping : maps query results to Java objects.

Transaction management : integrates with Spring or other transaction frameworks.

Connection‑pool integration : works with Apache DBCP, C3P0, HikariCP, etc.

Second‑level cache : shares cache across sessions.

After understanding these features, the article examines the internal components that support them.

2. MyBatis Overview

MyBatis architecture consists of three layers: the foundational support layer, the core processing layer, and the interface layer.

The typical usage flow includes defining an interface and XML configuration, loading and parsing the configuration, generating a proxy, and executing SQL.

Define the interface and its XML configuration file.

Load and parse the configuration files.

Generate the proxy class and execute the SQL.

Configuration parsing involves resource loading and parsing modules, after which SqlSessionFactory builds a Configuration object that stores all parsed information.

3. Configuration File Parsing

Parsing proceeds by loading the main configuration file ( mybatis-config.xml) into a Configuration object, then parsing details such as data sources, plugins, type aliases, and caches.

Key builder classes: XMLStatementBuilder: parses , , , and tags and builds MappedStatement objects. XMLMapperBuilder: parses Mapper.xml files, constructing mapping objects for SQL statements, parameters, results, and caches. XMLConfigBuilder: parses the main configuration file and builds global configuration objects.

4. Proxy Construction

After configuration, SqlSession.getMapper creates a proxy for the interface using MapperProxyFactory, MapperRegistry, and MapperProxy, relying on JDK dynamic proxies to return an implementation of the interface.

5. SQL Execution

SQL execution follows JDBC logic: create a Statement / PreparedStatement / CallableStatement, execute the query, and process the ResultSet.

Create the appropriate statement object.

Execute the SQL query.

Handle the ResultSet.

MyBatis offers methods such as selectOne(), selectList(), insert(), update(), and delete(). It parses dynamic SQL, performs parameter mapping, and maps results back to Java objects.

6. Summary

The overall workflow is: create a SqlSessionFactory, open a SqlSession, execute SQL via MyBatis methods, parse the SQL (including dynamic parts), map parameters and results, and finally return populated Java objects.