Design Patterns in MyBatis Source Code

MyBatis, a popular Java ORM framework, incorporates a variety of classic design patterns to decouple complex scenarios within its architecture.

Creational Patterns

Factory Pattern

SqlSessionFactory acts as a factory that creates session instances, encapsulating data source configuration, transaction factory construction, and executor creation.

Singleton Pattern

Configuration is implemented as a global singleton, ensuring a single instance throughout the session lifecycle and holding mappings, caches, interceptors, etc.

Builder Pattern

ResultMapBuilder and other *Builder classes construct complex objects step‑by‑step, isolating object construction from business logic.

Structural Patterns

Adapter Pattern

MyBatis defines a unified logging interface that adapts various logging frameworks (Log4j, Log4j2, SLF4J) to a common API.

Proxy Pattern

MapperProxy provides dynamic proxy implementations for DAO interfaces, delegating method calls to the executor chain.

Composite Pattern

SqlNode hierarchy composes XML dynamic SQL tags (if, where, foreach, etc.) into a tree structure representing “part‑whole” relationships.

Decorator Pattern

Cache decorators wrap simple executors to add second‑level caching behavior without modifying core execution logic.

Behavioral Patterns

Template Method

BaseExecutor defines the skeleton of query and update operations, allowing subclasses to customize specific steps.

Strategy Pattern

TypeHandler implementations encapsulate algorithms for handling different JDBC types, enabling interchangeable strategies.

Iterator Pattern

PropertyTokenizer iterates over property tokens during meta‑object reflection, abstracting collection traversal.

In total, MyBatis employs roughly ten design patterns, illustrating how sophisticated ORM frameworks leverage proven architectural solutions to manage complexity.