设计模式 之 装饰器模式

我的理解，就是一种组合

package com.test.pattern.decorator;

//组件对象的接口，可以给这些对象动态地添加职责
abstract class Component {
    public abstract void operation();
}

//具体组件
class ConcreteComponent extends Component {

    @Override
    public void operation() {

    }
}

//装饰器接口，维持一个指向组件对象的接口对象， 并定义一个与组件接口一致的接口
abstract class Decorator extends Component {

    /** 持有组件对象 */
    protected Component component;

    public Decorator(Component component) {
        this.component = component;
    }

    public void operation() {
        component.operation();
    }
}

//装饰器的具体实现对象
class ConcreteDecoratorA extends Decorator {
    public ConcreteDecoratorA(Component component) {
        super(component);
    }    

    private void operationFirst() {}
    private void operationLast() {}
    public void operation() {
        operationFirst();
        super.operation();
        operationLast();
    }
}

class ConcreteDecoratorB extends Decorator {
    public ConcreteDecoratorB(Component component) {
        super(component);
    }    

    private void operationFirst() {}
    private void operationLast() {}
    public void operation() {
        operationFirst();
        super.operation();
        operationLast();
    }
}

public class Client {
    public static void main(String[] args) {
        Component c1 = new ConcreteComponent();
        Decorator decoratorA = new ConcreteDecoratorA(c1);  //给对象透明的增加功能A并调用
        decoratorA.operation();
        Decorator decoratorB = new ConcreteDecoratorB(c1); //给对象透明的增加功能B并调用
        decoratorB.operation();
        Decorator decoratorBandA = new ConcreteDecoratorB(decoratorA);//装饰器也可以装饰具体的装饰对象，此时相当于给对象在增加A的功能基础上在添加功能B
        decoratorBandA.operation();
    }
}