工厂模式：专门负责将大量有共同接口的类实例化，工厂模式可以动态的决定将哪一个类实例化，不必事先知道每次要实例化哪一个类。工厂模式有以下几种形态：
- 简单工厂模式（simple factory）又称静态工厂模式。
- 工厂方法模式（Factory Method）又称多态工厂模式模式。
- 抽象工厂模式（Abstract Method）：又称工具箱。
1.简单工厂模式UML类图如图所示：
代码：
Fruit 抽象产品:
package com.lp.ecjtu.SimpleFactory; public interface Fruit { /** * 种植 */ public void plant(); /** * 生长 */ public void grow(); /** * 收货 */ public void harvest(); }
具体产品：这里包括Apple，Orange，Grape：
package com.lp.ecjtu.SimpleFactory; public class Apple implements Fruit{ @Override public void plant() { // TODO Auto-generated method stub System.out.println("Apples have been planted!"); } @Override public void grow() { // TODO Auto-generated method stub System.out.println("Apples is growing!"); } @Override public void harvest() { // TODO Auto-generated method stub System.out.println("Apples have been harvested!"); } }
package com.lp.ecjtu.SimpleFactory; public class Orange implements Fruit { @Override public void plant() { // TODO Auto-generated method stub System.out.println("Oranges have been planted!"); } @Override public void grow() { // TODO Auto-generated method stub System.out.println("Oranges is growing!"); } @Override public void harvest() { // TODO Auto-generated method stub System.out.println("Oranges have been harvested!"); } }
package com.lp.ecjtu.SimpleFactory; public class Grape implements Fruit { private boolean seedless; public boolean isSeedless() { return seedless; } public void setSeedless(boolean seedless) { this.seedless = seedless; } public void plant() { // TODO Auto-generated method stub System.out.println("Grapes have been planted!"); } public void grow() { // TODO Auto-generated method stub System.out.println("Grapes is growing!"); } public void harvest() { // TODO Auto-generated method stub System.out.println("Grapes have been growed!"); } }
工厂类：工厂模式的核心
package com.lp.ecjtu.SimpleFactory; public class FruitGarden { public FruitGarden(){} public static Fruit factoryFruit(String which) throws BadFruitException { if(which.equalsIgnoreCase("apple")){ return new Apple(); }else if(which.equalsIgnoreCase("orange")){ return new Orange(); }else if(which.equalsIgnoreCase("grape")){ return new Grape(); }else{ throw new BadFruitException("bad fruit"); } } }
FruitClient :
package com.lp.ecjtu.SimpleFactory; public class FruitClient { /** * @param args */ public static void main(String[] args) { // TODO Auto-generated method stub try { Fruit f = FruitGarden.factoryFruit("apple"); f.plant(); f.grow(); f.harvest(); System.out.println("********************************"); Fruit o = FruitGarden.factoryFruit("orange"); o.grow(); o.harvest(); o.plant(); } catch (BadFruitException e) { // TODO Auto-generated catch block e.printStackTrace(); } } }
运行输出：
Apples have been planted!
Apples is growing!
Apples have been harvested!
********************************
Oranges is growing!
Oranges have been harvested!
Oranges have been planted!
简单工厂模式的优点与缺陷：
优点：模式的核心是工厂，这个类含有必要的判断逻辑，可以决定在什么时候创建哪一个产品的实例。而客户端可以免除直接创建产品对象的责任，而仅仅负责"消费"产品。实现了对责任的额分割。
缺陷：工厂类是一个全能类，像上帝类，里面的方法是静态的，无法由子类继承，扩展性比较差，当有新的产品加入到系统中去，就需要修改工厂类。对"开-闭"
2.工厂方法设计模式（多态工厂模式）
工厂方法设计模式：弥补了简单工厂对“开-闭”原则支持不够的缺点，核心的工厂类不在负责所有产品的创建，而将具体创建工作交给了子类去做，这个核心类变成了一个抽象工厂角色。仅负责给出具体工厂子类必须的实现接口，而不接触那个产品类应该被实例化的这种细节。这样当系统需要加入新的产品的时候，不需要修改客户端，也没必要修改抽象工厂类或者其他已有的具体工厂角色，只需要向系统加入一个产品类以及它对应的工厂类。
下面我们对上面的水果类作物系统进行优化，在那个系统中有一个全知全能的园丁角色（FruitGarden），控制所有作物的种植，生长，收货。现在这个农场的规模变大了，而同时发生的是管理更专业化了。过去的全能人物没有了，每一种弄作物都有专门的园丁管理，形成规模化生产和专业化生产。
下图为工厂方法模式UML类图
代码实现：
抽象工厂角色：FruitGarden
package com.lp.ecjtu.FactoryMethod; public interface FruitGarden { /** * 工厂方法，抽象工厂角色 * @return */ public Fruit factory(); }
具体工厂角色：AppleGarden，GrapeGarden，OrangeGarden
package com.lp.ecjtu.FactoryMethod; public class AppleGarden implements FruitGarden{ /** * 工厂方法，抽象工厂角色 * @return */ public Fruit factory() { return new Apple(); } }
package com.lp.ecjtu.FactoryMethod; public class OrangeGarden implements FruitGarden{ /** * 工厂方法，抽象工厂角色 * @return */ public Fruit factory() { return new Orange(); } }
package com.lp.ecjtu.FactoryMethod; public class GrapeGarden implements FruitGarden{ /** * 工厂方法，抽象工厂角色 * @return */ public Fruit factory() { return new Grape(); } }
抽象产品角色：Fruit
package com.lp.ecjtu.FactoryMethod; public interface Fruit { /** * 种植 */ public void plant(); /** * 生长 */ public void grow(); /** * 收货 */ public void harvest(); }
具体产品角色：Apple，Orange，Grape
package com.lp.ecjtu.FactoryMethod; public class Apple implements Fruit { private int treeAge; public int getTreeAge() { return treeAge; } public void setTreeAge(int treeAge) { this.treeAge = treeAge; } @Override public void plant() { System.out.println("Apples have been planted!"); } @Override public void grow() { // TODO Auto-generated method stub System.out.println("Apples is growing!"); } @Override public void harvest() { // TODO Auto-generated method stub System.out.println("Apples have been harvested!"); } }
package com.lp.ecjtu.FactoryMethod; public class Orange implements Fruit { @Override public void plant() { System.out.println("Oranges have been planted!"); } @Override public void grow() { // TODO Auto-generated method stub System.out.println("Oranges is growing!"); } @Override public void harvest() { // TODO Auto-generated method stub System.out.println("Oranges have been harvested!"); } }
package com.lp.ecjtu.FactoryMethod; public class Grape implements Fruit { private String seedLess; public String isSeedLess() { return seedLess; } public void setSeedLess(String seedLess) { this.seedLess = seedLess; } @Override public void plant() { System.out.println("Grapes have been planted!"); } @Override public void grow() { // TODO Auto-generated method stub System.out.println("Grapes is growing!"); } @Override public void harvest() { // TODO Auto-generated method stub System.out.println("Grapes have been harvested!"); } }
水果Client：FruitClient
package com.lp.ecjtu.FactoryMethod; public class FruitClient { /** * @param args */ public static void main(String[] args) { FruitGarden fa = new AppleGarden(); Fruit f = fa.factory(); f.plant(); f.grow(); f.harvest(); System.out.println("********************************"); FruitGarden fo = new OrangeGarden(); Fruit o = fo.factory(); o.grow(); o.harvest(); o.plant(); System.out.println("********************************"); FruitGarden fg = new GrapeGarden(); Fruit g = fg.factory(); g.grow(); g.harvest(); g.plant(); } }
输出结果：
Apples have been planted!
Apples is growing!
Apples have been harvested!
********************************
Oranges is growing!
Oranges have been harvested!
Oranges have been planted!
********************************
Grapes is growing!
Grapes have been harvested!
Grapes have been planted!
Face your past without regret. Handle your present with confidence.Prepare for future without fear. keep the faith and drop the fear.
面对过去无怨无悔，把握现在充满信心，备战未来无所畏惧。保持信念，克服恐惧！一点一滴的积累，一点一滴的沉淀，学技术需要不断的积淀！
