定义

责任链模式的定义如下：

Avoid coupling the sender of a request to its receiver by giving more than one object a chance tohandle the request.Chain the receiving objects and pass the request along the chain until an objecthandles it.（使多个对象都有机会处理请求，从而避免了请求的发送者和接受者之间的耦合关系。将这些对象连成一条链，并沿着这条链传递该请求，直到有对象处理它为止。）

责任链模式的的UML图如下：

责任链模式

责任链模式的重点是在“链”上面，整个流程是由一条链去处理相似的请求并在链中决定谁来谁来处理这个请求。“链”是由多个处理者ConcreteHandler组成的。

责任链模式的通用代码如下：
Handler:

public abstract class Handler{
    private Handler nextHandler;

    public final Response handleMessage(Request request){  //对请求做出处理
        Response response = null;
        if(this.getHandlerLevel().equals(request.getRequestLevel())){  //判断是否是自己的处理级别
            response = this.echo(request);
        }else{
            if(this.nextHandler != null){  //判断是否有下一个处理者
                response = this.nextHandler.handleMessage(request);
            }else{
                //没有适当的处理者    
            }
        }
        return response;
    }

    public void setNext(Handler handler){  //设置下一个处理者
        this.nextHandler = handler;
    }

    protected abstract Level getHandlerLevel();  //获取处理级别
    protected abstract Response echo(Request response);  //进行处理
}

ConcreteHandleer1:

public class ConcreteHandler1 extends Handler{
    protected Level getHandlerLevel(){  //设置自己的处理级别
        return null;
    }

    protected Response echo(Request request){  //设置自己的处理逻辑
        return null;
    }
}

ConcreteHandler2:

public class ConcreteHandler2 extends Handler{
    protected Level getHandlerLevel(){  //设置自己的处理级别
        return null;
    }

    protected Response echo(Request request){  //设置自己的处理逻辑
        return null;
    }
}

接着来看具体的业务类：
Level:

public class Level{  
    //定义具体的等级业务类
}

Request:

public class Request {
    public Level getRequestLevel(){
        return null;
    }
}

Response:

public class Response{
    //定义具体的处理类
}

最后来创建具体的场景类来进行调用：

public class Client{
    public static void main(String[] args){
        Handler handler1 = new ConcreteHandler1();
        Handler handler2 = new ConcreteHandler2();
        handler1.setNext(handler2);  //设置处理的顺序
        Response response = handler1.handleMessage(new Request());
    }
}