职责链模式 Chain of Responsibility

职责链模式的作用在于职责转移，其实现实际上是一个链表

package chainofres;

public abstract class Handler {
    protected Handler successor;
    
    public abstract void action(int request);

    public void setSuccessor(Handler successor) {
        this.successor = successor;
    }    
}

package chainofres;

public class ConcurrentHandler1 extends Handler {
    @Override
    public void action(int request) {
        if (request < 100)
            System.out.println("Handler1 handle this");
        else if (this.successor != null)
            this.successor.action(request);
    }
}

package chainofres;

public class ConcurrentHandler2 extends Handler {
    @Override
    public void action(int request) {
        if (request >= 100 && request < 1000)
            System.out.println("Handler2 handle this");
        else if (this.successor != null)
            this.successor.action(request);
    }
}

package chainofres;

public class ConcurrentHandler3 extends Handler {
    @Override
    public void action(int request) {
        if (request >= 1000)
            System.out.println("Handler3 handle this");
        else if (this.successor != null)
            this.successor.action(request);
    }
}

package chainofres;

public class Client {
    public static void main(String[] args) {
        Handler h1 = new ConcurrentHandler1();
        Handler h2 = new ConcurrentHandler2();
        Handler h3 = new ConcurrentHandler3();        
        h1.setSuccessor(h2);
        h2.setSuccessor(h3);
        
        int request = 50;
        h1.action(request);
        request = 200;
        h1.action(request);
        request = 1500;
        h1.action(request);    
    }
}