Design Patterns Employed in the MyBatis Framework

MyBatis, a popular Java ORM framework, incorporates numerous design patterns throughout its more than 20,000 lines of source code, effectively decoupling complex scenarios and enhancing the overall architecture.

Creational Patterns

Factory Pattern : The SqlSessionFactory creates session instances, encapsulating data source configuration, transaction factories, and executor creation.

Singleton Pattern : The Configuration class ensures a single instance that holds mappings, caches, interceptors, and object factories across the session lifecycle.

Builder Pattern : Various *Builder classes (e.g., SqlSessionFactoryBuilder , XMLConfigBuilder ) construct complex objects step‑by‑step, isolating object creation from business logic.

Structural Patterns

Adapter Pattern : Provides a unified logging interface that adapts to different logging frameworks such as Log4j, Log4j2, and SLF4J.

Proxy Pattern : MapperProxy generates dynamic proxy implementations for DAO interfaces, delegating method calls to the executor chain.

Composite Pattern : SQL node hierarchy ( SqlNode and its subclasses) forms a tree structure to represent dynamic SQL fragments.

Decorator Pattern : Second‑level cache wraps the simple executor, adding caching behavior without altering the executor’s core logic.

Behavioral Patterns

Template Method Pattern : BaseExecutor defines the algorithm skeleton for query and update operations, allowing subclasses to customize specific steps.

Strategy Pattern : Different TypeHandler implementations encapsulate type‑specific data handling, enabling interchangeable algorithms.

Iterator Pattern : PropertyTokenizer iterates over property tokens for reflective object manipulation.

In total, MyBatis utilizes roughly ten distinct design patterns, demonstrating how a well‑engineered ORM framework leverages proven architectural solutions to manage complexity, promote code reuse, and facilitate future extensions.