設計模式——抽象工廠模式

5.

OO模式：抽象工廠模式——提供一個接口，用於創建相關或依賴對象的家族，而不需要明確指定具體類

例子：披薩店不同地域的原料準備

public class ClamPizza extends Pizza {
	PizzaIngredientFactory ingredientFactory;
 
	public ClamPizza(PizzaIngredientFactory ingredientFactory) {
		this.ingredientFactory = ingredientFactory;
	}
 
	void prepare() {
		System.out.println("Preparing " + name);
		dough = ingredientFactory.createDough();
		sauce = ingredientFactory.createSauce();
		cheese = ingredientFactory.createCheese();
		clam = ingredientFactory.createClam();
	}
}

public interface PizzaIngredientFactory {
 
	public Dough createDough();
	public Sauce createSauce();
	public Cheese createCheese();
	public Veggies[] createVeggies();
	public Pepperoni createPepperoni();
	public Clams createClam();
 
}

public abstract class Pizza {
	String name;

	Dough dough;
	Sauce sauce;
	Veggies veggies[];
	Cheese cheese;
	Pepperoni pepperoni;
	Clams clam;

	abstract void prepare();

	void bake() {
		System.out.println("Bake for 25 minutes at 350");
	}

	void cut() {
		System.out.println("Cutting the pizza into diagonal slices");
	}

	void box() {
		System.out.println("Place pizza in official PizzaStore box");
	}

	void setName(String name) {
		this.name = name;
	}

	String getName() {
		return name;
	}

	public String toString() {
		StringBuffer result = new StringBuffer();
		result.append("---- " + name + " ----\n");
		if (dough != null) {
			result.append(dough);
			result.append("\n");
		}
		if (sauce != null) {
			result.append(sauce);
			result.append("\n");
		}
		if (cheese != null) {
			result.append(cheese);
			result.append("\n");
		}
		if (veggies != null) {
			for (int i = 0; i < veggies.length; i++) {
				result.append(veggies[i]);
				if (i < veggies.length-1) {
					result.append(", ");
				}
			}
			result.append("\n");
		}
		if (clam != null) {
			result.append(clam);
			result.append("\n");
		}
		if (pepperoni != null) {
			result.append(pepperoni);
			result.append("\n");
		}
		return result.toString();
	}
}

public class CheesePizza extends Pizza {
	PizzaIngredientFactory ingredientFactory;
 
	public CheesePizza(PizzaIngredientFactory ingredientFactory) {
		this.ingredientFactory = ingredientFactory;
	}
 
	void prepare() {
		System.out.println("Preparing " + name);
		dough = ingredientFactory.createDough();
		sauce = ingredientFactory.createSauce();
		cheese = ingredientFactory.createCheese();
	}
}

public class ClamPizza extends Pizza {
	PizzaIngredientFactory ingredientFactory;
 
	public ClamPizza(PizzaIngredientFactory ingredientFactory) {
		this.ingredientFactory = ingredientFactory;
	}
 
	void prepare() {
		System.out.println("Preparing " + name);
		dough = ingredientFactory.createDough();
		sauce = ingredientFactory.createSauce();
		cheese = ingredientFactory.createCheese();
		clam = ingredientFactory.createClam();
	}
}

public abstract class PizzaStore {
 
	protected abstract Pizza createPizza(String item);
 
	public Pizza orderPizza(String type) {
		Pizza pizza = createPizza(type);
		System.out.println("--- Making a " + pizza.getName() + " ---");
		pizza.prepare();
		pizza.bake();
		pizza.cut();
		pizza.box();
		return pizza;
	}
}

public class NYPizzaStore extends PizzaStore {
 
	protected Pizza createPizza(String item) {
		Pizza pizza = null;
		PizzaIngredientFactory ingredientFactory = 
			new NYPizzaIngredientFactory();
 
		if (item.equals("cheese")) {
  
			pizza = new CheesePizza(ingredientFactory);
			pizza.setName("New York Style Cheese Pizza");
  
		} else if (item.equals("veggie")) {
 
			pizza = new VeggiePizza(ingredientFactory);
			pizza.setName("New York Style Veggie Pizza");
 
		} else if (item.equals("clam")) {
 
			pizza = new ClamPizza(ingredientFactory);
			pizza.setName("New York Style Clam Pizza");
 
		} else if (item.equals("pepperoni")) {

			pizza = new PepperoniPizza(ingredientFactory);
			pizza.setName("New York Style Pepperoni Pizza");
 
		} 
		return pizza;
	}
}

以下是上述類的關係圖：

比較工廠方法模式和抽象工廠模式：

這兩個模式雖然都屬於工廠模式，但有所不同。

工廠方法使用繼承：把對象的創建委託給子類，子類實現工廠方法來創建對象。

抽象工廠使用對象組合：對象的創建被實現在工廠接口所暴露出來的方法中。（當需要創建產品家族和想讓製造的相關產品集合起來時，此模式更適合）