职责链模式(Chain of Responsibility)（对象行为型）

最新推荐文章于 2024-07-11 09:25:15 发布

Rick-Lu

最新推荐文章于 2024-07-11 09:25:15 发布

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分类专栏：理解设计模式文章标签：设计模式

本文链接：https://blog.youkuaiyun.com/u010947098/article/details/73327394

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本文介绍职责链模式的设计理念与应用场景，通过具体实例演示了如何利用该模式解耦发送者与接收者，使得多个对象有机会处理同一请求。文章提供了完整的Java代码实现，并展示了请求在对象链中传递的过程。

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参考文档：

1.设计模式-可复用面向对象软件的基础

2.http://blog.youkuaiyun.com/hguisu/article/details/7547231（设计模式 ( 十二 ) 职责链模式(Chain of Responsibility)（对象行为型））

职责链模式(Chain of Responsibility)（对象行为型）

在这里讲的是书中实现的案例。

先看一下这个责任链模式的结构：

一个典型的对象结构可能如下图所示：

这一模式的想法是，给多个对象处理一个请求的机会，从而解耦发送者和接受者。该请求沿对象链传递直至其中一个对象处理它，如下图所示。

下面的交互框图(diagram) 说明了帮助请求怎样沿链传递:

代码实现：

下面的例子举例说明了在一个像前面描述的在线帮助系统中，职责链是如何处理请求的。

HelpHandler.java:

package com.rick.designpattern.chain_of_responsibility;

/**
 * Created by MyPC on 2017/6/16.
 */
public class HelpHandler {
    public static final int NO_HELP_TOPIC = -1;

    private HelpHandler successor;
    private int topic;


    public HelpHandler(HelpHandler helpHandler, int topic) {
        this.successor = helpHandler;
        this.topic = topic;
    }

    public void setHandler(HelpHandler h, int topic) {
        this.successor = h;
        this.topic = topic;
    }

    public boolean hasHelp() {
        return topic != NO_HELP_TOPIC;
    }

    public void handleHelp() {
        if (null != successor) {
            successor.handleHelp();
        }
    }
}
Widget.java:
package com.rick.designpattern.chain_of_responsibility;

/**
 * Created by MyPC on 2017/6/16.
 */
public class Widget extends HelpHandler {

    public Widget(Widget parent, int topic) {
        super(parent, topic);
    }
}
Dialog.java:
package com.rick.designpattern.chain_of_responsibility;

/**
 * Created by MyPC on 2017/6/16.
 */
public class Dialog extends Widget {

    public Dialog(HelpHandler helpHandler, int topic) {
        super(null, topic);
        setHandler(helpHandler, topic);
    }


    @Override
    public void handleHelp() {
        if (hasHelp()) {
            System.out.println("Dialog is handleHelp");
        } else {
            super.handleHelp();
        }
    }
}
Button.java:
package com.rick.designpattern.chain_of_responsibility;

/**
 * Created by MyPC on 2017/6/16.
 */
public class Button extends Dialog {

    public Button(Dialog parent, int topic) {
        super(parent, topic);
    }

    @Override
    public void handleHelp() {
        if (hasHelp()) {
            System.out.println("Button is handleHelp");
        } else {
            super.handleHelp();
        }
    }
}
Application.java:
package com.rick.designpattern.chain_of_responsibility;

/**
 * Created by MyPC on 2017/6/16.
 */
public class Application extends HelpHandler {
    public Application(int topic) {
        super(null, topic);
    }

    @Override
    public void handleHelp() {
        System.out.println("Application is handleHelp");
    }
}
Client.java:
package com.rick.designpattern.chain_of_responsibility;

import com.rick.designpattern.visitor.PricingVisitor;

/**
 * Created by MyPC on 2017/6/16.
 */
public class Client {
    public static final int PRINT_TOPIC = 1, PAPER_ORIENTATION_TOPIC = 2, APPLICATION_TOPIC = 3;


    public static void main(String[] args) {
        Application application = new Application(APPLICATION_TOPIC);
        Dialog dialog = new Dialog(application, PRINT_TOPIC);
        Button button = new Button(dialog, HelpHandler.NO_HELP_TOPIC);

        button.handleHelp();
    }
}