设计模式——抽象工厂模式

5.

OO模式：抽象工厂模式——提供一个接口，用于创建相关或依赖对象的家族，而不需要明确指定具体类

例子：披萨店不同地域的原料准备

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;}}

以下是上述类的关系图：

比较工厂方法模式和抽象工厂模式：

这两个模式虽然都属于工厂模式，但有所不同。

工厂方法使用继承：把对象的创建委托给子类，子类实现工厂方法来创建对象。

抽象工厂使用对象组合：对象的创建被实现在工厂接口所暴露出来的方法中。（当需要创建产品家族和想让制造的相关产品集合起来时，此模式更适合）