JAVA EE: Factory Design Pattern

Sunday, 22 September 2013

Factory Design Pattern - Key Points

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What is the Factory Design Pattern?

The Factory Design Pattern is a foundational creational pattern in object-oriented programming. Instead of using the new operator directly in client classes to instantiate concrete objects, the creation logic is delegated to a specialized factory class or method.

This design creates a clean separation of concerns, ensuring that client applications depend purely on interfaces or abstract classes rather than concrete implementations.

Essential Key Points to Remember

Loose Coupling: Decouples the client classes from the specific concrete classes they instantiate. Changes to concrete classes do not ripple through client code.
Single Responsibility Principle: Consolidates object creation rules, initialization, and validation into one dedicated location.
Open/Closed Principle: Adding a new implementation requires minimal updates inside the factory, leaving existing client logic untouched and closed for modification.
Encapsulated Creation Logic: If instantiating an object involves complex configuration or environment-dependent setup, the factory encapsulates those details neatly.
Coding to Interfaces: Clients work directly against common interfaces, allowing seamless swapping of implementations at runtime.

When Should You Apply It?

The Factory Pattern is ideal when:

A class cannot anticipate the exact sub-classes of objects it must create.
You want to centralize object creation to make future refactoring and unit testing easier.
You want to provide a library or framework where users can extend internal components without exposing concrete construction logic.