装饰模式以对客户端透明的方式扩展对象的功能,是继承关系的一个替代方案
一.UML示意图:
二.组成部分:
1. 抽象构件:原始的功能接口
2. 具体构件:具体的原始功能类
3. 装饰角色:持有具体构件类的对象,以便执行原有功能
4. 具体装饰:具体扩展的功能在这里
三.例子代码:使用装饰模式来演示一个对”行走”功能扩展的例子(听音乐+行走和唱歌+行走)
1. 抽象构件
package com.eekq.decorator;
publicinterface Component {
/**原始接口*/
publicvoid go();
}
2. 具体构件
package com.eekq.decorator;
publicclass ConcreteComponent implements Component {
publicvoid go() {
System.out.println("行走");
}
}
3.装饰角色来了
package com.eekq.decorator;
publicclass Decorator implements Component {
/**持有私有的原始构件*/
private Component component;
/**构造子,委派给原始构件*/
protected Decorator(Component component) {
this.component = component;
}
/**调用原始构件功能,通常就可直接把扩展功能加在此方法中*/
publicvoid go() {
this.component.go();
}
}
4.具体装饰(这里演示了两种扩展的情况,走路+听音乐和唱歌s)
(1).
package com.eekq.decorator;
publicclass ConcreteDecoratorListen extends Decorator {
/**构造子,相关初始化*/
public ConcreteDecoratorListen(Component component) {
super(component);
// code is here
}
/**商业逻辑,对原始构件功能的扩展*/
publicvoid go() {
listen("听音乐");//执行扩展功能
super.go();
}
privatevoid listen(Object obj){
System.out.println(obj);
}
}
(2).
package com.eekq.decorator;
publicclass ConcreteDecoratorSing extends Decorator {
/**构造子,相关初始化*/
public ConcreteDecoratorSing(Component component) {
super(component);
// code is here
}
/**商业逻辑,对原始构件功能的扩展*/
publicvoid go() {
super.go();
System.out.println(sing());;// 执行扩展功能
}
private String sing() {
return"唱歌";
}
}
5.客户端调用
package com.eekq.decorator;
publicclass Main {
publicstaticvoid main(String[] args) {
/**原始构件*/
Component component = new ConcreteComponent();
/**边听音乐,边走路*/
ConcreteDecoratorListen cdl = new ConcreteDecoratorListen(component);
cdl.go();
System.out.println();
/**边走路,边唱歌*/
ConcreteDecoratorSing cds = new ConcreteDecoratorSing(component);
cds.go();
}
}