责任链模式

//抽象处理者
public abstract class Handler{
    private Handler nextHandler;
    public final Response handleMessage(Request request){
        Resonpse response=null;
        if(this.getHandlerLevel().equals(requset.getRequestLevel())){
            response=this.echo(request);
        }else{
            if(this.nextHandler !=null){
                response=this.nextHandler.handleMessage(request);
            }else{
                //.....
            }
        }
        return response;
    }
    public void setNext(Handler _handler){
        this.nextHandler=_handler;
    }
    protected abstract Level getHandlerLevel();
    protected abstract Response echo(Request request);
}

//具体处理者
public class ConcreteHandler1 extends Handler{
    protected Response echo(Request request){
        return null;
    }
    protected Level getHandlerLevel(){
        return null;
    }
}

public class ConcreteHandler2 extends Handler{
    protected Response echo(Request request){
        return null;
    }
    protected Level getHandlerLevel(){
        return null;
    }
}

public class ConcreteHandler3 extends Handler{
    protected Response echo(Request request){
        return null;
    }
    protected Level getHandlerLevel(){
        return null;
    }
}

public class Level{}

public class Request{}

public class Response{}

//场景类
public class Client{
    public static void main(String[] args){
        Handler handler1=new ConcreteHanlder1();
        Handler handler2=new ConcreteHanlder2();
        Handler handler3=new ConcreteHanlder3();
        handler1.setNext(hanlder2);
        handler2.setNext(handler3);
        Response response=handler1.handlerMessage(new Request());
    }
}