设计模式-装饰器模式

作用: 可以在不改动原有代码的情况下，对现有的对象、行为进行新的层次的包装、装饰，增强原有的基本功能以提供更丰富的能力。

使用场景: 需要增强的目标存在抽象接口,且功能不足

结构图

使用
以墙面装修为例子

⏹1.定义一个墙面装修接口

public interface WallBeautify {
	
	// 墙面装修就需要操作
    void operation();
}

⏹2.接口的实现类

 
public class WallBeautifyClean implements WallBeautify {

    @Override
    public void operation() {
        System.out.println("开始清理墙面");
    }
}

⏹3.定义一个装饰器抽象类,对装修方法进行增强

装饰器也实现了基本的装修接口覆盖了原有的operation()方法,在此基础上进行增强

public abstract class WallBeautifyDecorator implements WallBeautify {

    private WallBeautify wallBeautify;
	
	// 传入WallBeautify接口的实现类
    public WallBeautifyDecorator(WallBeautify wallBeautify) {
        this.wallBeautify = wallBeautify;
    }
	
	// 覆盖原有的operation(方法,在此基础上进行增强)
    @Override
    public void operation() {
        wallBeautify.operation();
        decoration();
    }
	
	// 装饰器自定义的增强方法
    public abstract void decoration();
}

⏹4.定义装饰器抽象类的各个实现类

public class WallBeautifyPutty extends WallBeautifyDecorator {

    public WallBeautifyPutty(WallBeautify wallBeautify) {
        super(wallBeautify);
    }

    @Override
    public void decoration() {
        System.out.println("开始刮腻子");
    }
}

public class WallBeautifyPaint extends WallBeautifyDecorator {

    public WallBeautifyPaint(WallBeautify wallBeautify) {
        super(wallBeautify);
    }

    @Override
    public void decoration() {
        System.out.println("开始涂油漆");
    }
}

public class WallBeautifyHang extends WallBeautifyDecorator {

    public WallBeautifyHang(WallBeautify wallBeautify) {
        super(wallBeautify);
    }

    @Override
    public void decoration() {
        System.out.println("开始挂壁画");
    }
}

⏹5.增强

public class DecoratorTest {

    public static void main(String[] args) {
    
        // 清理墙面(未使用装饰器模式,功能单一,只能清理墙面)
        WallBeautify wallBeautifyClean = new WallBeautifyClean();
        wallBeautifyClean.operation();
        System.out.println("--------------");

        // 清理墙面 + 刮腻子
        // 使用了WallBeautifyPutty类对WallBeautifyClean进行了增强,不仅能清理墙面还能刮腻子
        WallBeautify wallBeautifyPutty = new WallBeautifyPutty(wallBeautifyClean);
        wallBeautifyPutty.operation();
        System.out.println("--------------");

        // 清理墙面 + 刮腻子 + 涂油漆
        // 使用WallBeautifyPaint类对WallBeautifyPutty进行了增强,不仅能清理墙面 + 刮腻子,还能涂油漆
        WallBeautify wallBeautifyPaint = new WallBeautifyPaint(wallBeautifyPutty);
        wallBeautifyPaint.operation();
        System.out.println("--------------");

        // 增加挂壁画功能
        WallBeautify wallBeautifyHang = new WallBeautifyHang(wallBeautifyPaint);
        wallBeautifyHang.operation();
        System.out.println("--------------");

        // 多层嵌套
        WallBeautify wbh = new WallBeautifyHang(new WallBeautifyPaint(
                new WallBeautifyPutty(new WallBeautifyClean())));
        wbh.operation();
        System.out.println("--------------");
    }
}

// -----------------输出结果-----------------

参考资料:
1.https://www.cnblogs.com/V1haoge/p/10472321.html
2.https://mp.weixin.qq.com/s?__biz=MzI3ODcxMzQzMw==&mid=2247558483&idx=1&sn=66e3d98e22c029c7ca141debfadff253