answered 2014-09-07 06:51:35 +0800

chillworld
5367 ● 4 ● 9
https://github.com/chillw...

updated 2014-09-09 08:04:35 +0800

You must ask yourself if server AAA wait for the response of server BBB.
Normally he does and your next line of code is when you have reach the answer.
I work also with webservices and you use it like a DB. (DB is normally also on server CCC).

Like I understand there are 2 possibility's.

First one :

You just call the webservice from your viewmodel through the service tier.
Now nothing is broken, and just do notifychanged.

Second one :

Put it in a thread if you need it to be in the background.
Nothing is wrong with creating a thread and then follow your links.

Edit :

Example how you could use thread and even notify the correct composer
It's not in ZK envirment but you found already the 2 links for threads so just implement that.

Composer.java :

/**
 *
 * @author chillworld
 */
public class Composer {

    private int number;

    public Composer(int number) {
        this.number = number;
    }

    public int getNumber() {
        return number;
    }

    public void callManagerForData() {
        Thread t = new CallWebService() {
            @Override
            public void run() {
                System.out.println("add obeserver  " + getNumber());
                Manager.INSTANCE.callWebService(this);
            }
        };
        t.start();
    }

    public void refresh(String data) {
        System.out.println("Refresh done of composer " + number + " with data : '" + data + "'");
    }

    abstract class CallWebService extends Thread implements Observer {

        @Override
        public void update(Observable o, Object arg) {
            refresh((String)arg);
        }
    }
}

Manager.java:

/**
 *
 * @author chillworld
 */
public enum Manager {
    INSTANCE;

    private AnswerWebService service = new AnswerWebService();

    public void callWebService(Observer o) {
        service.addObserver(o);
        try {
            Thread.sleep(2000);
        } catch (InterruptedException ex) {
        }
        service.postAnswer();
    }
}

AnswerWebService.java:

/**
 *
 * @author cossaer.f
 */
public class AnswerWebService {

    private final List<Observer> observers = Collections.synchronizedList(new ArrayList<Observer>());

    public void postAnswer() {
        // handle data
        synchronized (observers) {
            if (observers.size() > 0) {
                Observer o = observers.remove(0);
                o.update(null, "mine data");
            }
        }
    }

    public boolean addObserver (Observer o) {
        return observers.add(o);
    }
}

TestObserverPattern.java:

/**
 *
 * @author chillworld
 */
public class TestObserverPattern {

    public static void main(String[] args) {
       List<Composer> composers = new ArrayList<Composer>();
       for (int i = 0; i<20;i++) {
           composers.add(new Composer(i));
       }
       Collections.shuffle(composers);
       for (Composer c : composers) {
           c.callManagerForData();
       }
    }
}

Hope this could be usefull in your case.

Take care, cause I don't know how you link the asyn call to the answer, I created this case to link first call => first answer.
This is normally open for bugs when call's come at close time rate.

Greetz chill.