java design patterns - Chain Of reponsibility

指一个对象，要经过一系列的handler 来处理，例如java 的try catch block 里面去catch 不同的Exception. 

Usage in JDK:
java.util.logging.Logger#log()
javax.servlet.Filter #doFilter()

代码：

package chainofresponsibility;

//This class is the request object
class Number{
    private int number;

    public int getNumber(){
        return number;
    }

    public Number(int num){
        this.number = num;
    }
}

//This is the interface that acts as a chain link
interface Chain{
    public void setNext(Chain nextInChain);
    public void process(Number request);
}

class PositiveNumberProcessor implements Chain{
    private Chain nextInChain;

    @Override
    public void setNext(Chain c){
        nextInChain = c;
    }

    @Override
    public void process(Number request){
        if(request.getNumber() > 0){
            System.out.println("PositiveNumberProcessor :"+request.getNumber());
        }else{
            nextInChain.process(request);
        }
    }
}


class NegativeNumberProcessor implements Chain{

    private Chain nextInChain;

    @Override
    public void setNext(Chain c){
        nextInChain = c;
    }

    @Override
    public void process(Number request){
        if(request.getNumber() < 0){
            System.out.println("NegativeNumberProcessor :"+request.getNumber());
        }else{
            nextInChain.process(request);
        }
    }
}

class ZeroProcessor implements Chain{

    private Chain nextInChain;

    @Override
    public void setNext(Chain c){
        nextInChain = c;
    }

    @Override
    public void process(Number request){
        if(request.getNumber() == 0){
            System.out.println("ZeroProcessor :"+request.getNumber());
        }else{
            nextInChain.process(request);
        }
    }
}

public class ChainOfResponsibilityDemo {
    public static void main(String[] args){

        //configure Chain of reponsibility
        Chain c1 = new NegativeNumberProcessor();
        Chain c2 = new ZeroProcessor();
        Chain c3 = new PositiveNumberProcessor();
        c1.setNext(c2);
        c2.setNext(c3);

        //Calling chain of responsibility
        c1.process(new Number(99));
        c1.process(new Number(-30));
        c1.process(new Number(0));
        c1.process(new Number(100));
    }
}