Java设计模式之装饰器模式

1.装饰器模式的定义（保持接口，扩展功能）

　　Decorate装饰器，顾名思义，就是动态的给一个对象添加一些额外的职责，就好比对房子进行装修一样。

2.装饰器模式的特征

　　具有一个装饰对象。

　　必须拥有与被装饰对象相同的接口。

　　可与给被装饰对象添加额外的功能。

3.装饰器模式的典型应用，java.io包

4.装饰器模式的代码示例

/**
 * @Author long
 * @Date 2019/3/20 21:29
 */
public interface SourceAble {

    void operation();
}

/**
 * @Author long
 * @Date 2019/3/20 21:31
 */
public class Source implements SourceAble {

    @Override
    public void operation() {
        System.out.println("Source最原始的方法");
    }
}

/**
 * @Author long
 * @Date 2019/3/20 21:32
 */
public class SourceDecorateA implements SourceAble {

    private SourceAble sourceAble;

    public SourceDecorateA(SourceAble sourceAble){
        this.sourceAble = sourceAble;
    }

    @Override
    public void operation() {
        System.out.println("SourceDecorateA before");
        sourceAble.operation();
        System.out.println("SourceDecorateA after");
    }
}

/**
 * @Author long
 * @Date 2019/3/20 21:34
 */
public class SourceDecorateB implements SourceAble {

    private SourceAble sourceAble;

    public SourceDecorateB(SourceAble sourceAble){
        this.sourceAble = sourceAble;
    }

    @Override
    public void operation() {
        System.out.println("SourceDecorateB before");
        sourceAble.operation();
        System.out.println("SourceDecorateB after");
    }
}

/**
 * @Author long
 * @Date 2019/3/20 21:48
 */
public class App {

    public static void main(String[] args) {
        SourceAble source = new Source();
        source.operation();
        System.out.println("================");
        SourceAble decorateA = new SourceDecorateA(source);
        decorateA.operation();
        System.out.println("================");
        SourceAble decorateB = new SourceDecorateB(decorateA);
        decorateB.operation();
    }
}

Source最原始的方法
================
SourceDecorateA before
Source最原始的方法
SourceDecorateA after
================
SourceDecorateB before
SourceDecorateA before
Source最原始的方法
SourceDecorateA after
SourceDecorateB after