Java Decorator

The Decorator pattern is a structural design pattern that lets you attach new behaviors to objects by placing these objects inside special wrapper objects that contain the behaviors. The Decorator pattern provides a more flexible alternative to subclassing for extending functionality.

定义组件接口

java

        public interface Component {
    String operation();
}

创建具体组件

java

        public class ConcreteComponent implements Component {
    @Override
    public void operation() {
        System.out.println("ConcreteComponent operation");
    }
}

创建装饰器

java

        public abstract class Decorator implements Component {
    protected Component component;

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

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

实现具体装饰器

java

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

    @Override
    public void operation() {
        super.operation();
        addedBehavior();
    }

    private void addedBehavior() {
        System.out.println("ConcreteDecoratorA added behavior");
    }
}

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

    @Override
    public void operation() {
        super.operation();
        addedBehavior();
    }

    private void addedBehavior() {
        System.out.println("ConcreteDecoratorB added behavior");
    }
}

使用装饰器

java

        public class DecoratorPatternDemo {
    public static void main(String[] args) {
        Component component = new ConcreteComponent();
        Component decoratorA = new ConcreteDecoratorA(component);
        Component decoratorB = new ConcreteDecoratorB(decoratorA);

        decoratorB.operation();
    }
}