设计模式 - chain of Responsibility

Chain of Responsibility也就是职责链模式，通过使用链式结构，使对象都有机会处理请求，从而避免请求的发送者与接受者间的耦合关系。将这些对象连成链，并沿着该链传递请求，直到有对象处理为止。

实现的关键在于处理对象的转发机制，也就是如果我能处理，那么我处理，如果不能处理，就转发给后面的对象处理。但普通的实现方法中，该处理对象必须保有后面对象的引用，也就是仍存在一定程度的耦合。理想的情况是处理对象（handler）之间彼此不知对方，通过另外的机制完成对象传递。

Apache有开源框架实现职责链模式，用户可以通过配置xml来决定请求的处理顺序，而handler只需实现固定接口即可。

举个例子：

某皮包公司有各种总，但这些总共享三个秘书（不要理解错了），分为为lilyzhou, LucyWang和RuHua。总们签署的文件会交给秘书们处理，lilyzhou是大秘，LucyWang是二秘，RuHua是三秘。liliy不愿意处理的文件交给LucyWang，LucyWang不愿意处理的交给Ruhua。ruhua没有不愿意的权利，只能自己处理。

秘书们的特殊爱好如下：lilyzhou只处理boss.zhang签署的文件（她认为自己是秘书中的老大），LucyWang只处理boss.li签署的文件，Ruahua处理她们不愿意的处理的文件（有人的地方就有江湖啊）

下面贴出代码：

package com.inspur.jiyq.designpattern.responsibilitychain;
 
 
public interface Secretary {
    public void handover(ImporantFile file);
     
    public void dealWithIt(ImporantFile file);
}

package com.inspur.jiyq.designpattern.responsibilitychain;
 
public class ImporantFile {
    /**
     * 文件签名 boss.zhang, boss.li, bossWang
     */
    private String signature;
 
    public String getSignature() {
        return signature;
    }
 
    public void setSignature(String signature) {
        this.signature = signature;
    }
}

package com.inspur.jiyq.designpattern.responsibilitychain;
 
import com.inspur.jiyq.designpattern.responsibilitychain.impl.LilyZhou;
 
public class BossOnDuty {
    public static void main(String[] args)
    {
        ImporantFile file = new ImporantFile();
        file.setSignature("boss.sun");
         
        Secretary secretary = new LilyZhou();
        secretary.handover(file);
    }
}

package com.inspur.jiyq.designpattern.responsibilitychain.impl;
 
import com.inspur.jiyq.designpattern.responsibilitychain.ImporantFile;
import com.inspur.jiyq.designpattern.responsibilitychain.Secretary;
 
public class LilyZhou implements Secretary {
    private Secretary lucyWang = new LucyWang();
 
    @Override
    public void handover(ImporantFile file) {
        if (file.getSignature().equals("boss.zhang")) {
            dealWithIt(file);
        } else {
            lucyWang.handover(file);
        }
    }
 
    @Override
    public void dealWithIt(ImporantFile file) {
        // TODO Auto-generated method stub
        System.out.println("lilyzhou deal with it.");
    }
 
}

package com.inspur.jiyq.designpattern.responsibilitychain.impl;
 
import com.inspur.jiyq.designpattern.responsibilitychain.ImporantFile;
import com.inspur.jiyq.designpattern.responsibilitychain.Secretary;
 
public class LucyWang implements Secretary{
    private Secretary ruhua = new RuHua();
 
    @Override
    public void handover(ImporantFile file) {
        if (file.getSignature().equals("boss.li")) {
            dealWithIt(file);
        } else {
            ruhua.handover(file);
        }
    }
 
    @Override
    public void dealWithIt(ImporantFile file) {
        System.out.println("lucyWang deal with it.");
    }
 
}

package com.inspur.jiyq.designpattern.responsibilitychain.impl;
 
import com.inspur.jiyq.designpattern.responsibilitychain.ImporantFile;
import com.inspur.jiyq.designpattern.responsibilitychain.Secretary;
 
public class RuHua implements Secretary {
 
    @Override
    public void handover(ImporantFile file) {
        // RuHua can not deliever it to anybody else
        dealWithIt(file);
    }
 
    @Override
    public void dealWithIt(ImporantFile file) {
        System.out.println("RuHua deal with it.");
    }
 
}