设计模式系列:桥接模式

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概念

类的继承是类本身的垂直维度变化。如果需要水平维度上的变化扩展。继承是不好实现的。这时候我们可以引入桥接方式。桥接模式的做法是把变化部分抽象
出来，使变化部分与主类分离开来，从而将多个维度的变化彻底分离。最后，提供一个管理类来组合不同维度上的变化，通过这种组合来满足业务的需要。

实现

图片

Fruit:

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package com.littlehui.design.bridge;

/**
 * Created by littlehui on 2018/1/17.
 */
public interface Fruit {
    public void eat();
}

AbstractFruit:

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package com.littlehui.design.bridge;

/**
 * Created by littlehui on 2018/1/17.
 */
public class AbstractFruit implements Fruit {

    EatHandler eatHandler;

    public AbstractFruit(EatHandler eatHandler) {
        this.eatHandler = eatHandler;
    }

    @Override
    public void eat() {
        eatHandler.handle();
        System.out.println("开始吃水果。");
    }
}

Apple:

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package com.littlehui.design.bridge;

/**
 * Created by littlehui on 2018/1/17.
 */
public class Apple extends AbstractFruit {

    public Apple(EatHandler eatHandler) {
        super(eatHandler);
    }

    public void enjoy() {
        eat();
    }
}

WaterMelon:

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package com.littlehui.design.bridge;

/**
 * Created by littlehui on 2018/1/17.
 */
public class WaterMelon extends AbstractFruit {


    public WaterMelon(EatHandler eatHandler) {
        super(eatHandler);
    }

    public void eat() {
        super.eat();
        System.out.println("吃西瓜");
    }
}

EatHandler:

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package com.littlehui.design.bridge;

/**
 * Created by littlehui on 2018/1/17.
 */
public abstract class EatHandler {

    public void handle() {
        System.out.println("吃水果前处理。");
    }
}

PeelHandler :

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package com.littlehui.design.bridge;

/**
 * Created by littlehui on 2018/1/17.
 */
public class PeelHandler extends EatHandler {
    @Override
    public void handle() {
        super.handle();
        System.out.println("削皮");
    }
}

EatHandlerDivid:

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package com.littlehui.design.bridge;

/**
 * Created by littlehui on 2018/1/17.
 */
public class EatHandlerDivid extends EatHandler {
    public void handle() {
        super.handle();
        System.out.println("切块。");
    }
}
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package com.littlehui.design.bridge;

/**
 * Created by littlehui on 2018/1/17.
 */
public class Client {
    public static void main(String[] args) {
        EatHandler eatHandler = new PeelHandler();
        EatHandler eatHandler1 = new EatHandlerDivid();
        Fruit apple = new Apple(eatHandler);
        Fruit waterMelon = new WaterMelon(eatHandler1);
        apple.eat();
        waterMelon.eat();
    }
}

如上代码解释：

  • 抽象部分 1：吃水果接口抽象，2.吃水果前处理抽象。
  • 具体实现部分 : apple里的enjoy

这里就分离了水果关于吃水果和水果处理的部分。Apple里的enjoy是具体的实现，可以eat，可以做其他操作。我们可以切换 水果处理 Handle来改变 Apple
enjoy具体时动作。

场景

略

总结

桥接的重点是 将实现解耦，抽象和实现独立开，不影响对方。
桥接一般用于跨多个平台的图形和窗口系统上。当需要不同的方式改变借口和实现时，可以用桥接。