装饰器模式

1.装饰器模式的定义

动态地给一个对象添加一些额外的职责。就增加功能来说，装饰模式比生成子类更为灵活

2.装饰器模式的UML图

Component：组件对象的接口，可以给这些对象动态的添加职责

ConcreteComponent：具体的组件对象，实现组件对象接口，通常就是被装饰器装饰的原始对象，也就是可以给这个对象添加职责

Decorator：所有装饰器的抽象父类，需要定义一个与组件接口一致的接口，并持有一个Component对象，其实就是持有一个被装饰的对象

3.代码实现

public abstract class Component{public void operation();}public class ConcreteComponent extends Component{   public void operation(){      }}public abstract class Decorator extends Component{protected Component component;public Decorator(Component component){      this.component=component;}public void operation(){   this.component.operation();}}public class ConcreteDecoratorA extends Decorator{   private String addedState;   public String getAddedState(){      return this.addedState;   }   public void setAddedState(String addedState){       this.addedState=addedState;   }    public ConcreteDecoratorA(Component component){        this.component=component;}public void operation(){    this.component=compnent;}}public class ConcreteDecoratorB extends Decorator{   private String addedState;   public String getAddedState(){      return this.addedState;   }   public void setAddedState(String addedState){       this.addedState=addedState;   }    public ConcreteDecoratorB(Component component){        this.component=component;}public void operation(){    this.component=compnent;}}public class  Client{public static void main(String[] args){    Component component=new ConreteComponent();Decorator decorator=new ConcreteDecoratorA(component);decorator.operation();}}

4.装饰模式的本质：动态组合