Java Vector immer ohne ersichtlichen Grund blockiert

Question

Ich bin wahrscheinlich etwas falsch zu machen, aber das ist, was passiert:

registrieren ich einen Hörer, warten auf sie und aufgerufen werden, wenn er ausgeführt wird, und fordert „Vector.clear ()“ es einrastet. Das Problem tritt in der „pipeMsgEvent“ Methode, hier ist es das, nicht so freundlich aussehende, Code (wenn Sie möchten, gehen Sie direkt zu: „Das ist wichtig“ Zeilen):

public class JxtaCustomer implements PipeMsgListener {
    public static final int ANSWER_OK        = 0;
    public static final int ANSWER_TIMEOUT   =-1;
    public static final int ANSWER_NOT_ASKED =-2;
    public static final int ANSWER_WORKING   =-3;

    public static final int REQ_SENT         = 0;
    public static final int REQ_INV_PIPE_ID  =-1;
    public static final int REQ_INV_PIPE_IO  =-2;
    public static final int REQ_INV_GROUP_ID =-3;

    protected int answer;

    protected JxtaGenericAdvertisement serviceAdv = null;
    protected JxtaNode ThePeer = null;

    JxtaBiDiPipe myBiDiPipe = null;
    protected Vector<Entry> output = null;

    public JxtaCustomer(JxtaGenericAdvertisement adv, JxtaNode peer)
    {
        ThePeer = peer;
        serviceAdv = new JxtaGenericAdvertisement((Element)adv.getDocument(new MimeMediaType("text/xml")));

        answer = ANSWER_NOT_ASKED;
        Vector<Entry> output = new Vector<Entry>();
    }

    public void pipeMsgEvent(PipeMsgEvent event)
    {
        System.out.println("It Works! Uhuuu");
        // We received a message
        Message message = event.getMessage();

        System.out.println("Lets GO! Uhuuu");
        Message.ElementIterator elIt = message.getMessageElementsOfNamespace( serviceAdv.getName() );

        System.out.println("A little bit more");
        answer = ANSWER_WORKING;

        System.out.println("enter");

        // This is important: Here I get stuck, "clear"
        // never appears on the screen
        output.clear();
        System.out.println("clear");
        while (elIt.hasNext()) {
            MessageElement mElem = elIt.next();
            System.out.println(mElem.getElementName() + " " + mElem.toString());
            output.add( new Entry( mElem.getElementName(), mElem.toString() ) );
        }
        System.out.println("leave");

        answer = ANSWER_OK;
    }

    public int sendRequest(Vector<Entry> params)
    {
        try {

            // Creating Pipe Advertisement
            String pipeAdvType = PipeAdvertisement.getAdvertisementType();
            PipeAdvertisement pipeAd = (PipeAdvertisement)AdvertisementFactory.newAdvertisement(pipeAdvType);

            URI pipeURI = new URI(serviceAdv.getPipeID());
            pipeAd.setPipeID( IDFactory.fromURI(pipeURI) );
            pipeAd.setType(PipeService.UnicastType);
            pipeAd.setName(serviceAdv.getName() + " Service Pipe");
            pipeAd.setDescription("Created by " + serviceAdv.getName());

            // Creating Group
            JxtaGroup jxgp = ThePeer.getGroupFromID( serviceAdv.getGroupID() );
            if (null == jxgp)
                return REQ_INV_GROUP_ID;

            PeerGroup group = jxgp.getPeerGroup();
            if (null == group)
                return REQ_INV_GROUP_ID;

            // This is important: In the JxtaBiDiPipe call I register
            // the callback, while I have access to the code, I think
            // the problem is in my code
            myBiDiPipe = new JxtaBiDiPipe( group, pipeAd, 30000, this);

            if (myBiDiPipe.isBound()) {
                Thread.sleep(500);

                Message myMessage = new Message();

                if (0 == params.size())
                    params.add( new Entry("dummy", "null") );

                for (int i=0; i<params.size(); i++) {
                    String Key = params.get(i).getKey();
                    String Value = params.get(i).getValue();
                    StringMessageElement strMsgElem = new StringMessageElement( Key, Value, null);
                    myMessage.addMessageElement( serviceAdv.getName(), strMsgElem);
                }

                myBiDiPipe.sendMessage(myMessage);

                answer = ANSWER_TIMEOUT;

                return REQ_SENT;
            }
        } catch (URISyntaxException e){
            e.printStackTrace();

            return REQ_INV_PIPE_ID;
        } catch (IOException e) {
            return REQ_INV_PIPE_IO;
        } catch (Exception e) {
            e.printStackTrace();
        }

        return REQ_INV_PIPE_IO;
    }

    public Vector<Entry> getResponse()
    {
        Vector<Entry> results = new Vector<Entry>();

        if (ANSWER_OK != answer)
            return results;

        // This is important: I always call "getState()" and check its value
        // before calling this method, so you can say it's guaranteed to be
        // called after answer = ANSWER_OK, which never happens because of the
        // lock
        for (int i=0; i<output.size(); i++)
            results.add( output.get(i) );

        return results;
    }

    public int getState()
    {
        int count = 10;

        return answer;
    }
}

Ich erzeuge immer JxtaCustomer wie folgt aus:

JxtaCustomer customer = new JxtaCustomer(adv, ThePeer);
Vector<Entry> params = new Vector<Entry>();

params.add( new Entry("key1", "value1") );
params.add( new Entry("key2", "value2") );

customer.sendRequest(params);

while(JxtaCustomer.ANSWER_OK != customer.getState()) {
   // I was actually using synchronized locks and timed waits
   // but since I'm stuck there I'm using this nonsense instead
}

Vector<Entry> response = customer.getResponse();

Hier ist, wo im Code I „Schlaf“, „wait“ nennen oder erstelle ich ein „synchronisiert“ (das letzte ist nie)

$ grep synchronized $(find . -name "*.java")

$ grep sleep $(find . -name "*.java")
./Src/net/ubi/jxta/JxtaCustomer.java:                Thread.sleep(500);

$ grep wait $(find . -name "*.java")
./App/ExampleServices/SimpleSigner.java:    boolean waiting = false;
./App/ExampleServices/SimpleSigner.java:        waiting = true;
./App/ExampleServices/SimpleSigner.java:        return (waiting && JxtaCustomer.ANSWER_OK == customer.getState());
./App/ExampleServices/SimpleSigner.java:        if (!waiting)
./App/ExampleServices/SimpleSigner.java:            waiting = false;
./App/ExampleServices/SimpleSigner.java:            return "Error: Response not ready, wait more time\n";

Answer 1

Ihr Konstruktor legt eine lokale Variable namens Ausgang und nicht die Membervariable, Sie haben

Vector<Entry> output = new Vector<Entry>();

, wenn es sein sollte

output = new Vector<Entry>();

Also, später, wenn Sie anrufen output.clear() Sie eine Null-Zeiger-Ausnahme ausgelöst, wenn es darum, weshalb die folgenden Zeilen Code nicht ausgeführt werden soll.

Compiler-Warnungen wie „nicht verwendete lokale Variablen“ kann diese Art von Fehlern helfen erkennen.