Java设计模式：工厂方法模式（Factory Method Pattern）

定义

工厂方法模式定义了一个创建对象的接口，但由子类决定要实例化的类是哪一个。工厂方法让类把实例推迟到子类。

UML类图

说明

Prouduct：所有的产品都必须实现这个共同的接口，并实现多态

Creator：它是一个类，实现了所有操纵产品的方法，但不实现工厂方法，并且所有的它的子类都必须实现这个抽象的factoryMethod()方法。

ConcreteCreator：它必须实现factoryMethod(),以实际制造出产品，并且它负责创建一个或多个具体产品，只有ConcreteCreator类知道如何创建这些产品。

事例

上一次的简单工厂，以一个披萨店为例；这里同样如此，说明它如何从一个简单工厂扩展为工厂方法模式；

这里，披萨店要开分店

纽约披萨店：奶酪、蛤蜊、意式辣肠、蔬菜等类型的披萨

芝加哥披萨店：奶酪、蛤蜊、意式辣肠、蔬菜等类型的披萨

两种店都供应这些披萨，但同种名称的披萨的细节却不同，每家店都供应其独特的披萨。

UML类图

代码

Pizza.java 抽象类，披萨超类

package com.jing.factory;import java.util.ArrayList;public abstract class Pizza {String name; // 名字String dough;// 面包String sauce;// 酱料// 佐料ArrayList<String> topping = new ArrayList<String>();public String getName() {return name;}public void prepare() {System.out.println("Preparing " + name);}public void bake() {System.out.println("Baking " + name);}public void cut() {System.out.println("Cutting " + name);}public void box() {System.out.println("Boxing " + name);}public String toString() {StringBuffer display = new StringBuffer();display.append("---- " + name + " ---------\n");display.append(dough + "\n");display.append(sauce + "\n");for (int i = 0; i < topping.size(); ++i) {display.append((String) topping.get(i) + "\n");}return display.toString();}}

ChicagoStyleCheesePizza.java 芝加哥风格的奶酪披萨

package com.jing.factory;public class ChicagoStyleCheesePizza extends Pizza {public ChicagoStyleCheesePizza() {name = "Chiacago Cheese Pizza"; // 奶酪 披萨dough = "Regular Crust"; // 普通的披萨饼皮sauce = "Marinara Pizza Sauce"; // 蕃茄酱，沙司topping.add("Fresh Mozzarella");// 新鲜的马苏里拉奶酪topping.add("Parmesan");// 芝士}public void cut(){System.out.println("Chicago cutting the pizza into square slices");}}

ChicagoStyleClamPizza.java 芝加哥风格的蛤蜊披萨

package com.jing.factory;public class ChicagoStyleClamPizza extends Pizza {public ChicagoStyleClamPizza(){name = "Chiacago Clam Pizza";//蛤蜊dough = "Thin crust";// 薄的面皮sauce = "White garlic sauce";//白的蒜酱topping.add("Clams");topping.add("Grated Parmesan cheese");// 巴马干酪}public void cut(){System.out.println("Chicago cutting the pizza into square slices");}}

ChicagoStylePepperoniPizza.java 芝加哥风格意式辣肠

package com.jing.factory;public class ChicagoStylePepperoniPizza extends Pizza {public ChicagoStylePepperoniPizza(){name = "Chiacago Pepperoni Pizza";//意大利辣肠dough = "Curst";// 面皮sauce = "Marinara sauce";// 蕃茄酱topping.add("Sliced Pepperoni");// 切片辣肠topping.add("Sliced Onion");    // 切片洋葱topping.add("Grated parmesan cheese");//芝士奶酪}public void cut(){System.out.println("Chicago cutting the pizza into square slices");}}

ChicagoStyleVeggiePizza.java 芝加哥风格的蔬菜披萨

package com.jing.factory;public class ChicagoStyleVeggiePizza extends Pizza {public ChicagoStyleVeggiePizza(){name = "Chiacago Veggie Pizza"; // 蔬菜dough = "Crust";sauce = "Marinara sauce";// 蕃茄酱topping.add("Shredded mozzaredlla");// 意大利干酪topping.add("Grated parmesan");// 芝士topping.add("Diced onion");// 切丁洋葱topping.add("Sliced mushrooms");//切片蘑菇topping.add("Sliced red pepper");//切片红花椒topping.add("Sliced black olives");//橄榄}public void cut(){System.out.println("Chicago cutting the pizza into square slices");}}

NYStyleCheesePizza.java 纽约风格的奶酪披萨

package com.jing.factory;public class NYStyleCheesePizza extends Pizza {public NYStyleCheesePizza() {name = "NY Cheese Pizza"; // 奶酪 披萨dough = "Regular Crust"; // 普通的披萨饼皮sauce = "Marinara Pizza Sauce"; // 蕃茄酱，沙司topping.add("Fresh Mozzarella");// 新鲜的马苏里拉奶酪topping.add("Parmesan");// 芝士}}

NYStyleClamPizza.java 纽约风格的蛤蜊披萨

package com.jing.factory;public class NYStyleClamPizza extends Pizza {public NYStyleClamPizza(){name = "NY Clam Pizza";//蛤蜊dough = "Thin crust";// 薄的面皮sauce = "White garlic sauce";//白的蒜酱topping.add("Clams");topping.add("Grated Parmesan cheese");// 巴马干酪}}

NYStylePepperoniPizza.java 纽约风格的意式辣肠披萨

package com.jing.factory;public class NYStylePepperoniPizza extends Pizza {public NYStylePepperoniPizza(){name = "NY Pepperoni Pizza";//意大利辣肠dough = "Curst";// 面皮sauce = "Marinara sauce";// 蕃茄酱topping.add("Sliced Pepperoni");// 切片辣肠topping.add("Sliced Onion");    // 切片洋葱topping.add("Grated parmesan cheese");//芝士奶酪}}

NYStyleVeggiePizza.java 纽约风格的蔬菜披萨

package com.jing.factory;public class NYStyleVeggiePizza extends Pizza {public NYStyleVeggiePizza(){name = "NY Veggie Pizza"; // 蔬菜dough = "Crust";sauce = "Marinara sauce";// 蕃茄酱topping.add("Shredded mozzaredlla");// 意大利干酪topping.add("Grated parmesan");// 芝士topping.add("Diced onion");// 切丁洋葱topping.add("Sliced mushrooms");//切片蘑菇topping.add("Sliced red pepper");//切片红花椒topping.add("Sliced black olives");//橄榄}}

PizzaStore.java 披萨店抽象超类

package com.jing.factory;//public class PizzaStore {//改成抽象类public abstract class PizzaStore {//SimplePizzaFactory factory;////public PizzaStore(SimplePizzaFactory factory){//this.factory = factory;//}abstract Pizza createPizza(String type);public Pizza orderPizza(String type){//pizza = factory.createPizza(type);Pizza pizza = createPizza(type);System.out.println("------- Making a " + pizza.getName()+ " --------- ");pizza.prepare();pizza.bake();pizza.cut();pizza.box();return pizza;}}

ChicagoPizzaStore.java 芝加哥披萨店

package com.jing.factory;public class ChicagoPizzaStore extends PizzaStore{public Pizza createPizza(String type){Pizza pizza = null;if (type.equals("cheese")){pizza = new ChicagoStyleCheesePizza();} else if (type.equals("pepperoni")){pizza = new ChicagoStylePepperoniPizza();} else if (type.equals("clam")){pizza = new ChicagoStyleClamPizza();} else if (type.equals("veggie")){pizza = new ChicagoStyleVeggiePizza();}return pizza;}}

NYPizzaStore.java 纽约披萨店

package com.jing.factory;public class NYPizzaStore extends PizzaStore {public Pizza createPizza(String type){Pizza pizza = null;if (type.equals("cheese")){pizza = new NYStyleCheesePizza();} else if (type.equals("pepperoni")){pizza = new NYStylePepperoniPizza();} else if (type.equals("clam")){pizza = new NYStyleClamPizza();} else if (type.equals("veggie")){pizza = new NYStyleVeggiePizza();}return pizza;}}

Test.java 测试类

package com.jing.factory;public class Test {/** * @param args */public static void main(String[] args) {// TODO Auto-generated method stub// 纽约披萨店PizzaStore nyStore = new NYPizzaStore();// 芝加哥披萨店PizzaStore chicagoStore = new ChicagoPizzaStore();Pizza pizza = nyStore.orderPizza("cheese");System.out.println("Ethan ordered a " + pizza.getName() + "\n");pizza = chicagoStore.orderPizza("cheese");System.out.println("Joel ordered a " + pizza.getName() + "\n");pizza = nyStore.orderPizza("clam");System.out.println("Ethan ordered a " + pizza.getName() + "\n");pizza = chicagoStore.orderPizza("clam");System.out.println("Joel ordered a " + pizza.getName() + "\n");pizza = nyStore.orderPizza("pepperoni");System.out.println("Ethan ordered a " + pizza.getName() + "\n");pizza = chicagoStore.orderPizza("pepperoni");System.out.println("Joel ordered a " + pizza.getName() + "\n");pizza = nyStore.orderPizza("veggie");System.out.println("Ethan ordered a " + pizza.getName() + "\n");pizza = chicagoStore.orderPizza("veggie");System.out.println("Joel ordered a " + pizza.getName() + "\n");}}

输出

------- Making a NY Cheese Pizza --------- Preparing NY Cheese PizzaBaking NY Cheese PizzaCutting NY Cheese PizzaBoxing NY Cheese PizzaEthan ordered a NY Cheese Pizza------- Making a Chiacago Cheese Pizza --------- Preparing Chiacago Cheese PizzaBaking Chiacago Cheese PizzaChicago cutting the pizza into square slicesBoxing Chiacago Cheese PizzaJoel ordered a Chiacago Cheese Pizza------- Making a NY Clam Pizza --------- Preparing NY Clam PizzaBaking NY Clam PizzaCutting NY Clam PizzaBoxing NY Clam PizzaEthan ordered a NY Clam Pizza------- Making a Chiacago Clam Pizza --------- Preparing Chiacago Clam PizzaBaking Chiacago Clam PizzaChicago cutting the pizza into square slicesBoxing Chiacago Clam PizzaJoel ordered a Chiacago Clam Pizza------- Making a NY Pepperoni Pizza --------- Preparing NY Pepperoni PizzaBaking NY Pepperoni PizzaCutting NY Pepperoni PizzaBoxing NY Pepperoni PizzaEthan ordered a NY Pepperoni Pizza------- Making a Chiacago Pepperoni Pizza --------- Preparing Chiacago Pepperoni PizzaBaking Chiacago Pepperoni PizzaChicago cutting the pizza into square slicesBoxing Chiacago Pepperoni PizzaJoel ordered a Chiacago Pepperoni Pizza------- Making a NY Veggie Pizza --------- Preparing NY Veggie PizzaBaking NY Veggie PizzaCutting NY Veggie PizzaBoxing NY Veggie PizzaEthan ordered a NY Veggie Pizza------- Making a Chiacago Veggie Pizza --------- Preparing Chiacago Veggie PizzaBaking Chiacago Veggie PizzaChicago cutting the pizza into square slicesBoxing Chiacago Veggie PizzaJoel ordered a Chiacago Veggie Pizza