装饰者模式

Posted 2021-02-01 linbq1911

1.定义：在不改变原有对象的基础之上，将功能附加到对象上；
　　　   提供了比继承更有弹性的替代方案(扩展原有对象功能)。

2.类型：结构型

3.适用场景：扩展一个类的功能或给一个类添加附加职责；
　　　　动态的给一个对象添加功能，这些功能可以再动态的撤销。

4.优点：继承的有力补充，比继承灵活，不改变原有对象的情况下给一个对象扩展功能；
　　　  通过使用不同装饰类以及这些装饰类的排列组合，可以实现不同效果；
　　　  符合开闭原则。

5.缺点：会出现更多的代码，更多的类，增加程序复杂性；
　　　   动态装饰时，多层装饰时会更复杂。

6.相关设计模式：代理模式，适配器模式。

7.实例目录package

8.实例UML类图

9.代码

 1 package com.geely.design.pattern.structural.decorator.v1;
 2 
 3 public class Battercake {
 4     public String getDesc(){
 5         return "煎饼";
 6     }
 7     public int cost(){
 8         return 8;
 9     }
10 }

 1 package com.geely.design.pattern.structural.decorator.v1;
 2 
 3 public class BattercakeWithEgg extends Battercake {
 4     @Override
 5     public String getDesc() {
 6         return super.getDesc() + " 加一个鸡蛋";
 7     }
 8 
 9     @Override
10     public int cost() {
11         return super.cost() + 1;
12     }
13 }

 1 package com.geely.design.pattern.structural.decorator.v1;
 2 
 3 public class BattercakeWithEggSausage extends BattercakeWithEgg {
 4     @Override
 5     public String getDesc() {
 6         return super.getDesc() + "加一根香肠";
 7     }
 8 
 9     @Override
10     public int cost() {
11         return super.cost()+2;
12     }
13 }

 1 package com.geely.design.pattern.structural.decorator.v1;
 2 
 3 public class Test {
 4     public static void main(String[] args) {
 5         Battercake battercake = new Battercake();
 6         System.out.println(battercake.getDesc()+ "销售价格：" + battercake.cost());
 7 
 8         BattercakeWithEgg battercakeWithEgg = new BattercakeWithEgg();
 9         System.out.println(battercakeWithEgg.getDesc()+ "销售价格：" + battercakeWithEgg.cost());
10 
11         BattercakeWithEggSausage battercakeWithEggSausage = new BattercakeWithEggSausage();
12         System.out.println(battercakeWithEggSausage.getDesc()+ "销售价格：" + battercakeWithEggSausage.cost());
13     }
14 }

1 package com.geely.design.pattern.structural.decorator.v2;
2 
3 public abstract class ABattercake {
4     public abstract String getDesc();
5     public abstract int cost();
6 }

 1 package com.geely.design.pattern.structural.decorator.v2;
 2 
 3 public class Battercake extends ABattercake {
 4     @Override
 5     public String getDesc() {
 6         return "煎饼";
 7     }
 8 
 9     @Override
10     public int cost() {
11         return 8;
12     }
13 }

 1 package com.geely.design.pattern.structural.decorator.v2;
 2 
 3 public abstract class AbstractDecorator extends ABattercake {
 4     private ABattercake aBattercake;
 5 
 6     public AbstractDecorator(ABattercake aBattercake) {
 7         this.aBattercake = aBattercake;
 8     }
 9 
10     protected abstract void doSomething();
11 
12     @Override
13     public String getDesc() {
14         return aBattercake.getDesc();
15     }
16 
17     @Override
18     public int cost() {
19         return aBattercake.cost();
20     }
21 }

 1 package com.geely.design.pattern.structural.decorator.v2;
 2 
 3 public class EggDecorator extends AbstractDecorator {
 4     public EggDecorator(ABattercake aBattercake) {
 5         super(aBattercake);
 6     }
 7 
 8     @Override
 9     protected void doSomething() {
10 
11     }
12 
13     @Override
14     public String getDesc() {
15         return super.getDesc()+" 加一个鸡蛋";
16     }
17 
18     @Override
19     public int cost() {
20         return super.cost() + 1;
21     }
22 }

 1 package com.geely.design.pattern.structural.decorator.v2;
 2 
 3 public class SausageDecorator extends AbstractDecorator {
 4     public SausageDecorator(ABattercake aBattercake) {
 5         super(aBattercake);
 6     }
 7 
 8     @Override
 9     protected void doSomething() {
10 
11     }
12 
13     @Override
14     public String getDesc() {
15         return super.getDesc()+" 加一根香肠";
16     }
17 
18     @Override
19     public int cost() {
20         return super.cost()+2;
21     }
22 }

 1 package com.geely.design.pattern.structural.decorator.v2;
 2 
 3 public class Test {
 4     public static void main(String[] args) {
 5         ABattercake aBattercake;
 6         aBattercake = new Battercake();
 7         aBattercake = new EggDecorator(aBattercake);
 8         aBattercake = new EggDecorator(aBattercake);
 9         aBattercake = new SausageDecorator(aBattercake);
10 
11         System.out.println(aBattercake.getDesc()+ "销售价格：" + aBattercake.cost());
12     }
13 }