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 {
    @Override
    public 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;
    }

    @Override
    public 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);
    }

    @Override
    public 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);
    }

    @Override
    public 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();
    }
}