Abstract Factory

Tags
Design Pattern, Java

Introduction

• Purpose
  • Provide an interface that delegates creation calls to one or more concrete classes in order to deliver specific objects.
• Use When
  • The creation of objects should be independent of the system utilizing them.
  • Systems should be capable of using multiple families of objects.
  • Families of objects must be used together.
  • Libraries must be published without exposing implementation details.
  • Concrete classes should be decoupled from clients.
• Characteristics
  • Delegates object creation to a factory object.
  • Uses composition and delegation.

Participants

• AbstractFactory
  • Declares an interface for operations that create abstract product objects.
• ConcreteFactory
  • Implements the operations to create product objects.
• AbstractProduct
  • Declares an interface for a type of product object.
• ConcreteProduct
  • Defines a product object to be created by the corresponding concrete factory.
  • Implements the AbstractProduct interface.
• Client
  • Uses only interfaces declared by AbstractFactory and AbstractProduct classes.

How to Use (Example)

• Abstract Factory

  public interface IngredientFactory {
      public IngredientA createIngredientA();
      public IngredientB createIngredientB();
      public IngredientC createIngredientC();
  }
  

• Concrete Factory

  public class MyIngredientFactory implements IngredientFactory {
      public IngredientA createIngredientA() {
          return new MyIngredientA();
      }
  
      public IngredientB createIngredientB() {
          return new MyIngredientB();
      }
  
      public IngredientC createIngredientC() {
          return new MyIngredientC();
      }
  }
  

• Abstract Product

  public abstract class Product {
      IngredientA ingredientA;
      IngredientB ingredientB;
      IngredientC ingredientC;
  
      public abstract void prepare();
  }
  

• Concrete Product

  public class MyProduct extends Product {
      MyIngredientFactory myIngredientFactory;
  
      public MyProduct(MyIngredientFactory myIngredientFactory) {
          this.myIngredientFactory = myIngredientFactory;
      }
  
      public void prepare() {
          ingredientA = myIngredientFactory.createIngredientA();
          ingredientB = myIngredientFactory.createIngredientB();
          ingredientC = myIngredientFactory.createIngredientC();
      }
  }