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设计模式之工厂模式
本章分三部分：简单工厂，工厂方法模式，抽象工厂模式。
一、简单工厂：简单工厂其实不是一个设计模式，只是一种编程习惯。示例如下：
PizzaStore.java
package headfirst.factory.pizzas;
public class PizzaStore {
SimplePizzaFactory factory;
public PizzaStore(SimplePizzaFactory factory) {
this.factory = factory;
}
public Pizza orderPizza(String type) {
Pizza pizza;
pizza = factory.createPizza(type);
pizza.prepare();
pizza.bake();
pizza.cut();
pizza.box();
return pizza;
}
}SimplePizzaFactory.java
package headfirst.factory.pizzas;
public class SimplePizzaFactory {
public Pizza createPizza(String type) {
Pizza pizza = null;
if (type.equals("cheese")) {
pizza = new CheesePizza();
} else if (type.equals("pepperoni")) {
pizza = new PepperoniPizza();
} else if (type.equals("clam")) {
pizza = new ClamPizza();
} else if (type.equals("veggie")) {
pizza = new VeggiePizza();
}
return pizza;
}
}Pizza类是一个抽象基类，其他具体Pizza类均继承自他，在此不再列出代码。
测试：package headfirst.factory.pizzas;
public class PizzaTestDrive {
public static void main(String[] args) {
SimplePizzaFactory factory = new SimplePizzaFactory();
PizzaStore store = new PizzaStore(factory);
Pizza pizza = store.orderPizza("cheese");
System.out.println("We ordered a " + pizza.getName() + "\n");
pizza = store.orderPizza("veggie");
System.out.println("We ordered a " + pizza.getName() + "\n");
}
}二、工厂方法模式
此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化推迟到子类。
简单描述：由子类决定要创建的具体类是哪一个
示例：PizzaStore.java(createPizza()声明成抽象方法，由子类实现，从而由子类决定要创建的具体pizza是什么)
package headfirst.factory.pizzafm;
public abstract class PizzaStore {
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;
}
}NYPizzaStore.java(具体的pizza店类)
package headfirst.factory.pizzafm;
public class NYPizzaStore extends PizzaStore {
Pizza createPizza(String item) {
if (item.equals("cheese")) {
return new NYStyleCheesePizza();
} else if (item.equals("veggie")) {
return new NYStyleVeggiePizza();
} else if (item.equals("clam")) {
return new NYStyleClamPizza();
} else if (item.equals("pepperoni")) {
return new NYStylePepperoniPizza();
} else return null;
}
}其他代码就不贴了，这两个类已经足于展示工厂方法模式的原理。
测试：
package headfirst.factory.pizzafm;
public class PizzaTestDrive {
public static void main(String[] args) {
PizzaStore nyStore = new NYPizzaStore();
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");
}
}三、抽象工厂模式
定义：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。
简单描述：允许客户创建对象的家族，而无需指定他们的具体类
OO原则：依赖抽象，不要依赖具体类。
示例：
PizzaIngredientFactory.java(原料工厂抽象类)
package headfirst.factory.pizzaaf;
public interface PizzaIngredientFactory {
public Dough createDough();
public Sauce createSauce();
public Cheese createCheese();
public Veggies[] createVeggies();
public Pepperoni createPepperoni();
public Clams createClam();
}
NYPizzaIngredientFactory.java(具体类)
package headfirst.factory.pizzaaf;
public class NYPizzaIngredientFactory implements PizzaIngredientFactory {
public Dough createDough() {
return new ThinCrustDough();
}
public Sauce createSauce() {
return new MarinaraSauce();
}
public Cheese createCheese() {
return new ReggianoCheese();
}
public Veggies[] createVeggies() {
Veggies veggies[] = { new Garlic(), new Onion(), new Mushroom(), new RedPepper() };
return veggies;
}
public Pepperoni createPepperoni() {
return new SlicedPepperoni();
}
public Clams createClam() {
return new FreshClams();
}
}
Pizza.java(抽象类)
package headfirst.factory.pizzaaf;
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();
}
}
CheesePizza.java(pizza具体类，利用相关的工厂生产原料，所生产的原料依赖所使用的工厂，Pizza类根本不关心这些原料，它只知道如何制作Pizza。)
package headfirst.factory.pizzaaf;
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();
}
}PizzaStore.java(抽象类)
package headfirst.factory.pizzaaf;
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;
}
}NYPizzaStore.java（具体类）
package headfirst.factory.pizzaaf;
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;
}
}
其他类不列出，测试类如下：
package headfirst.factory.pizzaaf;
public class PizzaTestDrive {
public static void main(String[] args) {
PizzaStore nyStore = new NYPizzaStore();
PizzaStore chicagoStore = new ChicagoPizzaStore();
Pizza pizza = nyStore.orderPizza("cheese");
System.out.println("Ethan ordered a " + pizza + "\n");
pizza = chicagoStore.orderPizza("cheese");
System.out.println("Joel ordered a " + pizza + "\n");
pizza = nyStore.orderPizza("clam");
System.out.println("Ethan ordered a " + pizza + "\n");
pizza = chicagoStore.orderPizza("clam");
System.out.println("Joel ordered a " + pizza + "\n");
pizza = nyStore.orderPizza("pepperoni");
System.out.println("Ethan ordered a " + pizza + "\n");
pizza = chicagoStore.orderPizza("pepperoni");
System.out.println("Joel ordered a " + pizza + "\n");
pizza = nyStore.orderPizza("veggie");
System.out.println("Ethan ordered a " + pizza + "\n");
pizza = chicagoStore.orderPizza("veggie");
System.out.println("Joel ordered a " + pizza + "\n");
}
}
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