设计模式-结构模式-装饰模式

装饰模式（Decorator Pattern）：动态地给一个对象增加一些额外的职责，就增加对象功能来说，装饰模式比生成子类实现更为灵活。装饰模式是一种对象结构型模式。

//首先，定义一个组件接口：
public interface Component {void operation();
}
//然后，创建一个实现了该接口的具体组件类
public class ConcreteComponent implements Component {@Overridepublic void operation() {System.out.println("ConcreteComponent operation");}
}
//接下来，创建一个抽象装饰器类，它实现了相同的接口并持有一个组件对象的引用：
public abstract class Decorator implements Component {protected Component component;public Decorator(Component component) {this.component = component;}@Overridepublic void operation() {component.operation();}
}
//最后，创建具体装饰器类，继承自抽象装饰器并添加额外功能：
public class ConcreteDecoratorA extends Decorator {public ConcreteDecoratorA(Component component) {super(component);}@Overridepublic void operation() {super.operation();addedFunctionalityA();}public void addedFunctionalityA() {System.out.println("Added functionality A");}
}public class ConcreteDecoratorB extends Decorator {public ConcreteDecoratorB(Component component) {super(component);}@Overridepublic void operation() {super.operation();addedFunctionalityB();}public void addedFunctionalityB() {System.out.println("Added functionality B");}
}
现在，你可以创建客户端代码来展示如何使用装饰器：
public class DecoratorPatternExample {public static void main(String[] args) {Component component = new ConcreteComponent();System.out.println("Operation of ConcreteComponent:");component.operation();System.out.println("\nDecorating with ConcreteDecoratorA:");component = new ConcreteDecoratorA(component);component.operation();System.out.println("\nDecorating with ConcreteDecoratorB:");component = new ConcreteDecoratorB(component);component.operation();}
}