一、不使用工厂
披萨项目：要方便披萨品种的扩展、要便于维护、要能运行时扩展
披萨族的设计：
抽象Pizza类，有四个方法：prepare（）、bake(),cut(),box()
实际的披萨：GreekPizza和CheesePizza
披萨工厂设计：if…else … if …else
1、抽象Pizza类
package com.java.jikexueyuan.pizzastore.pizza;
public abstract class Pizza {
protected String name;
public abstract void prepare();
public void bake()
{
System.out.println(name+" baking;");
}
public void cut()
{
System.out.println(name+" cutting;");
}
public void box()
{
System.out.println(name+" boxing;");
}
public void setname(String name)
{
this.name=name;
}
}
2、实际的披萨类
1）、CheesePizza
package com.java.jikexueyuan.pizzastore.pizza;
public class CheesePizza extends Pizza {
@Override
public void prepare() {
// TODO Auto-generated method stub
super.setname("CheesePizza");
System.out.println(name+" preparing;");
}
}
2）、GreekPizza
package com.java.jikexueyuan.pizzastore.pizza;
public class GreekPizza extends Pizza {
@Override
public void prepare() {
// TODO Auto-generated method stub
super.setname("GreekPizza");
System.out.println(name+" preparing;");
}
}
3、一般OrderPizza实现类
package com.java.jikexueyuan.pizzastore;
public class OrderPizza {
public OrderPizza() {
Pizza pizza = null;
String ordertype;
do {
ordertype = gettype(); //控制台输入
if (ordertype.equals("cheese")) {
pizza = new CheesePizza();
} else if (ordertype.equals("greek")) {
pizza = new GreekPizza();
} else if (ordertype.equals("pepper")) {
pizza = new PepperPizza();
} else if (ordertype.equals("chinese")) {
pizza = new ChinesePizza();
} else {
break;
}
pizza.prepare();
pizza.bake();
pizza.cut();
pizza.box();
} while (true);
}
}
简单工厂总结：如果要扩展新的pizza，就要将OrderPizza这个简单工厂停下来修改其中代码。
4、怎么改进呢？
将变化的地方抽取出来，使用简单工厂来封装，这样就不用停止orderPizza的运行，如下：
二、简单工厂（从主类提取实例化（变化）部分）
定义一个实例化披萨对象的类，封装创建对象的代码
1、SimplePizzaFactory类
public class SimplePizzaFactory {
public Pizza CreatePizza(String ordertype) {
Pizza pizza = null;
if (ordertype.equals("cheese")) {
pizza = new CheesePizza();
} else if (ordertype.equals("greek")) {
pizza = new GreekPizza();
} else if (ordertype.equals("pepper")) {
pizza = new PepperPizza();
}
return pizza;
}
}
2、新的OrderPizza类
public class OrderPizza {
SimplePizzaFactory mSimplePizzaFactory;
public OrderPizza(SimplePizzaFactory mSimplePizzaFactory) {
setFactory(mSimplePizzaFactory);
}
public void setFactory(SimplePizzaFactory mSimplePizzaFactory) {
Pizza pizza = null;
String ordertype;
this.mSimplePizzaFactory = mSimplePizzaFactory;
do {
ordertype = gettype();
pizza = mSimplePizzaFactory.CreatePizza(ordertype);
if (pizza != null) {
pizza.prepare();
pizza.bake();
pizza.cut();
pizza.box();
}
} while (true);
}
三、工厂方法模式
将对象的实例化推迟到子类
困惑：披萨项目加盟店
解决：将披萨对象实例化功能抽象成抽象方法，在不同加盟店具体实现功能；
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1、抽象的OrderPizza
package com.java.jikexueyuan.pizzastore.method;
public abstract class OrderPizza {
public OrderPizza() {
Pizza pizza = null;
String ordertype;
do {
ordertype = gettype();
pizza = createPizza(ordertype);
pizza.prepare();
pizza.bake();
pizza.cut();
pizza.box();
} while (true);
}
// 方法抽象出来
abstract Pizza createPizza(String ordertype);
}
2、实际的OrderPizza
1）、纽约的NYOrderPizza
package com.java.jikexueyuan.pizzastore.method;
public class NYOrderPizza extends OrderPizza {
@Override
Pizza createPizza(String ordertype) {
Pizza pizza = null;
if (ordertype.equals("cheese")) {
pizza = new NYCheesePizza();
} else if (ordertype.equals("pepper")) {
pizza = new NYPepperPizza();
}
return pizza;
}
}
2）、伦敦的LDOrderPizza
public class LDOrderPizza extends OrderPizza {
@Override
Pizza createPizza(String ordertype) {
Pizza pizza = null;
if (ordertype.equals("cheese")) {
pizza = new LDCheesePizza();
} else if (ordertype.equals("pepper")) {
pizza = new LDPepperPizza();
}
return pizza;
}
}
四、抽象工厂模式
定义一个接口，用于创建相关或有依赖关系的对象族，而无需明确指定具体类。
1、抽象AbsFactory类
package com.java.jikexueyuan.pizzastore.absfactory;
public interface AbsFactory {
public Pizza CreatePizza(String ordertype) ;
}
2、具体实现类
1）、伦敦LDFactory
package com.java.jikexueyuan.pizzastore.absfactory;
public class LDFactory implements AbsFactory {
@Override
public Pizza CreatePizza(String ordertype) {
Pizza pizza = null;
if (ordertype.equals("cheese")) {
pizza = new LDCheesePizza();
} else if (ordertype.equals("pepper")) {
pizza = new LDPepperPizza();
}
return pizza;
}
}
2）纽约NYFactory
package com.java.jikexueyuan.pizzastore.absfactory;
public class NYFactory implements AbsFactory {
@Override
public Pizza CreatePizza(String ordertype) {
Pizza pizza = null;
if (ordertype.equals("cheese")) {
pizza = new NYCheesePizza();
} else if (ordertype.equals("pepper")) {
pizza = new NYPepperPizza();
}
return pizza;
}
}
3、OrderPizza类（AbsFactory的具体工厂传进来创建pizza对象）
package com.java.jikexueyuan.pizzastore.absfactory;
public class OrderPizza {
AbsFactory mFactory;
public OrderPizza(AbsFactory mFactory) {
setFactory(mFactory);
}
public void setFactory(AbsFactory mFactory) {
Pizza pizza = null;
String ordertype;
this.mFactory = mFactory;
do {
ordertype = gettype();
pizza = mFactory.CreatePizza(ordertype);
if (pizza != null) {
pizza.prepare();
pizza.bake();
pizza.cut();
pizza.box();
}
} while (true);
}
}
五、依赖抽象原则
1、变量不要持有具体类的引用
例如，OrderPizza类中创建披萨的变量；