设计模式----Chain of Responsibility(职责链)模式

GOF：使多个对象都有机会处理请求，从而避免请求的发送者和接收者之间的耦合关系。将这些对象连成一条链，并沿着这条链传递请求，直到有一个对象处理它为止。

 

Chain of Responsibility(职责链)模式其实也挺简单的。通俗的来说就是当一个请求发到我这里，我能处理就给处理，不能处理就推给其他人去处理。也就是说接受请求的对象形成一个链，请求在这个链上传递，直到链上的某一个对象决定处理此请求。发出这个请求的客户可以在不影响客户端的情况下动态的重新组织链和分配责任。也可以这样理解，你到一个地方去办一件事情，本来很小的事情，但是办事的人互相推诿扯皮，一个推一个，最后有个心善的人把事情给你办了。

 

下面是一个简单的例子：

 

下面是UML图：

参考文献：

GOF《设计模式》 by GOF

《Think in Patterns》 by Bruce Eckel

《设计模式》 by 板桥里人

http://zhenyulu.cnblogs.com/articles/65850.html

package ChainOfResponsibility;

public abstract class Handler
...{
    protected Handler successor;
    
    public void setSuccessor(Handler successor)
    ...{
        this.successor = successor;
    }//end setSuccessor(...)
    
    abstract public void handleRequest(int request);

}//end abstract class Handler

package ChainOfResponsibility;

public class ConcreteHandler1 extends Handler
...{
    public void handleRequest(int request)
    ...{
        if(request >= 0 && request < 10)...{
            System.out.println(this);
            System.out.println("handled request " + request);
        }else...{
            if(successor != null)
                successor.handleRequest(request);
        }
    }//end handleRequest(...)
    
}//End class ConcreteHandler1

package ChainOfResponsibility;

public class ConcreteHandler2 extends Handler
...{
    public void handleRequest(int request)
    ...{
        if(request >= 10 && request < 20)...{
            System.out.println(this);
            System.out.println("handled request " + request);
        }else...{
            if(successor != null)
                successor.handleRequest(request);
        }
    }//end handleRequest(...)
    
}//end class ConcreteHandler2

package ChainOfResponsibility;

public class ConcreteHandler3 extends Handler
...{
    public void handleRequest(int request)
    ...{
        if(request >= 20 && request < 30)...{
            System.out.println(this);
            System.out.println("handled request " + request);
        }else...{
            if(successor != null)
                successor.handleRequest(request);
        }
    }//end handleRequest(...)
}//end class ConcreteHandler3

下面是调用：
package ChainOfResponsibility;

public class ChainOfResponsibilityPattern
...{
    Handler h1 = new ConcreteHandler1();
    Handler h2 = new ConcreteHandler2();
    Handler h3 = new ConcreteHandler3();
    
    public ChainOfResponsibilityPattern()
    ...{
        //do something....
    }//end ChainOfResponsibilityPattern()
    
    public void showChainOfResponsibilityPattern()
    ...{
        h1.setSuccessor(h2);
        h2.setSuccessor(h3);
        int[] request = ...{2, 5, 14, 22, 18, 3, 27, 20};
        for(int i = 0; i<request.length; ++i)
            h1.handleRequest(request[i]);
    }//end showChainOfResponsibilityPattern()
    
    public static void main(String[] args)
    ...{
        System.out.println("-----------------");
        System.out.println("The Chain Of Responsibility Pattern!");
        ChainOfResponsibilityPattern corp = new ChainOfResponsibilityPattern();
        corp.showChainOfResponsibilityPattern();
        System.out.println("-----------------");
    }//end main(...)
    
}//End Class ChainOfResponsibilityPattern