java.rmi.NoSuchObjectException但添加了静态引用

Question

i'm implementing a client/server app with java RMI, client and server are in different packages in the same project (and of course they run on the same machine) and interfaces are defined in a "common" package.When i try to get one of the two remote object i get the aforementioned excepition. I've read some SO answers where people sugget to add a static reference to remote object so they can be never collected, but this doesn't work!

here is the code of the client and server

NotificheServiceProxy

public class NotificheServiceProxy implements INotificheService
{

    @Override
    public ArrayList <NotificaDTO> generaNotifiche(String autostrada, Date data, Date oraInizio, Date oraFine)
    {
        try 
        {
            RMIClient client = new RMIClient ("localhost" , 1099);
            INotificheService service = (INotificheService) client.getService(INotificheService.class);
            return service.generaNotifiche(autostrada, data, oraInizio, oraFine);
        }
        catch (RemoteException ex)
        {
            Logger.getLogger(TrattaServiceProxy.class.getName()).log(Level.SEVERE, null, ex);
            return null;
        }
        catch (NotBoundException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return null;
    }
}

RMIClient

    public class RMIClient
    {
        private Registry reg;

     public RMIClient  (String url , int port) throws RemoteException
    {
        reg = LocateRegistry.getRegistry(url, port);
    }


    public Remote getService(Class service) throws NotBoundException, RemoteException
    {
        RMIMapping RMIMappingAnn = (RMIMapping) service.getAnnotation(RMIMapping.class);

        return reg.lookup(RMIMappingAnn.name());
    }

}

NotificheService (server side)

public class NotificheService implements INotificheService 
{
    private static NotificheService instance;


    @Override
    public ArrayList<NotificaDTO> generaNotifiche(String autostrada, Date data, Date oraInizio, Date oraFine) throws RemoteException
    {
        instance = this;
        return new NotificheBusinessLogic().generaNotifiche(autostrada, data, oraInizio, oraFine);
    }
}

scServerConfig (server main)

public class SCServerConfig
{
    public static RMIServer server;
    public static void main (String[] args)
    {
         server = new RMIServer(1099);

        //avvia il server ed esporta oggetti remoti
        server.start().export(TrattaService.class).export(NotificheService.class);

        //Other stuff


RMIServer (starts server and provide method for remote objects exporting

public class RMIServer
{

    private Registry reg;
    private int regPort;



    public RMIServer (int regPort)
    {
        this.regPort = regPort;
    }

    public RMIServer start()
    {
        try
        {
            reg = LocateRegistry.createRegistry(regPort);
            System.out.println("SERVER OK");

        }
        catch (RemoteException ex)
        {
            Logger.getLogger(RMIServer.class.getName()).log(Level.SEVERE, null, ex);
        }

        return this;
    }

    public RMIServer export (Class object)
    {
        try
        {

            RMIMapping RMIMappingAnn = (RMIMapping) object.getInterfaces()[0].getAnnotation(RMIMapping.class);
            Remote tmp = UnicastRemoteObject.exportObject((Remote)object.newInstance(), 0);

            reg.rebind( RMIMappingAnn.name() , tmp );

            System.out.println("oggetto remoto esportato " + object);

        } 
        catch (InstantiationException ex)
        {
            System.err.println("InstantiationExeception!!\ncause:\n 1. il costruttore dell' oggetto remoto non deve avere argomenti");
        }
        catch (IllegalAccessException ex)
        {
            Logger.getLogger(RMIServer.class.getName()).log(Level.SEVERE, null, ex);
        }
        catch (RemoteException ex)
        {
            Logger.getLogger(RMIServer.class.getName()).log(Level.SEVERE, null, ex);
        }


        return this;
    }

 }

Each interface is annotated with @RMIMapping annotation that provides the object binding name. But i'm sure that the problem doesn'come from this

This is for me a real mistery, this is the stacktrace......many thanks for help!

ott 03, 2014 5:13:17 PM it.csbeng.speedcontrolsystem.addettoApp.proxy.NotificheServiceProxy generaNotifiche
SEVERE: null
java.rmi.NoSuchObjectException: no such object in table
    at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(StreamRemoteCall.java:273)
    at sun.rmi.transport.StreamRemoteCall.executeCall(StreamRemoteCall.java:251)
    at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:160)
    at java.rmi.server.RemoteObjectInvocationHandler.invokeRemoteMethod(RemoteObjectInvocationHandler.java:194)
    at java.rmi.server.RemoteObjectInvocationHandler.invoke(RemoteObjectInvocationHandler.java:148)
    at $Proxy3.generaNotifiche(Unknown Source)
    at it.csbeng.speedcontrolsystem.addettoApp.proxy.NotificheServiceProxy.generaNotifiche(NotificheServiceProxy.java:25)
    at it.csbeng.speedcontrolsystem.addettoApp.coordinator.AddettoAppCoordinator.generaNotifiche(AddettoAppCoordinator.java:17)
    at it.csbeng.speedcontrolsystem.addettoApp.boundary.AddettoInteraction.generaNotificheEvent(AddettoInteraction.java:179)
    at it.csbeng.speedcontrolsystem.addettoApp.boundary.AddettoInteraction.access$000(AddettoInteraction.java:15)
    at it.csbeng.speedcontrolsystem.addettoApp.boundary.AddettoInteraction$1.mousePressed(AddettoInteraction.java:78)
    at java.awt.AWTEventMulticaster.mousePressed(AWTEventMulticaster.java:280)
    at java.awt.Component.processMouseEvent(Component.java:6502)
    at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
    at java.awt.Component.processEvent(Component.java:6270)
    at java.awt.Container.processEvent(Container.java:2229)
    at java.awt.Component.dispatchEventImpl(Component.java:4861)
    at java.awt.Container.dispatchEventImpl(Container.java:2287)
    at java.awt.Component.dispatchEvent(Component.java:4687)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
    at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4489)
    at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
    at java.awt.Container.dispatchEventImpl(Container.java:2273)
    at java.awt.Window.dispatchEventImpl(Window.java:2719)
    at java.awt.Component.dispatchEvent(Component.java:4687)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:723)
    at java.awt.EventQueue.access$200(EventQueue.java:103)
    at java.awt.EventQueue$3.run(EventQueue.java:682)
    at java.awt.EventQueue$3.run(EventQueue.java:680)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
    at java.awt.EventQueue$4.run(EventQueue.java:696)
    at java.awt.EventQueue$4.run(EventQueue.java:694)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:693)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at it.csbeng.speedcontrolsystem.addettoApp.coordinator.AddettoAppCoordinator.generaNotifiche(AddettoAppCoordinator.java:20)
    at it.csbeng.speedcontrolsystem.addettoApp.boundary.AddettoInteraction.generaNotificheEvent(AddettoInteraction.java:179)
    at it.csbeng.speedcontrolsystem.addettoApp.boundary.AddettoInteraction.access$000(AddettoInteraction.java:15)
    at it.csbeng.speedcontrolsystem.addettoApp.boundary.AddettoInteraction$1.mousePressed(AddettoInteraction.java:78)
    at java.awt.AWTEventMulticaster.mousePressed(AWTEventMulticaster.java:280)
    at java.awt.Component.processMouseEvent(Component.java:6502)
    at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
    at java.awt.Component.processEvent(Component.java:6270)
    at java.awt.Container.processEvent(Container.java:2229)
    at java.awt.Component.dispatchEventImpl(Component.java:4861)
    at java.awt.Container.dispatchEventImpl(Container.java:2287)
    at java.awt.Component.dispatchEvent(Component.java:4687)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
    at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4489)
    at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
    at java.awt.Container.dispatchEventImpl(Container.java:2273)
    at java.awt.Window.dispatchEventImpl(Window.java:2719)
    at java.awt.Component.dispatchEvent(Component.java:4687)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:723)
    at java.awt.EventQueue.access$200(EventQueue.java:103)
    at java.awt.EventQueue$3.run(EventQueue.java:682)
    at java.awt.EventQueue$3.run(EventQueue.java:680)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
    at java.awt.EventQueue$4.run(EventQueue.java:696)
    at java.awt.EventQueue$4.run(EventQueue.java:694)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:693)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)

EDIT: @EJP before that, i've done something like

public class RemoteObject implements IRemoteObject
{
    private static RemoteObject instance;

    public RemoteObject ()
    {
       instance = this;
    }

    public someType someMethod (...)
}

but it throwed the same exception. Furthermore, as you can see, in scServerConfig there is a public static RMIServer server;

which encapsulates a Registry reference. if these thing i've done are correct, i think that adding static references may not be enough, even tough "suddendly" started to work for me. Am I wrong?

Answer 1

java.rmi.NoSuchObjectException but static reference added

It isn't added. You're trying to call the remote method that adds it. You're failing at that, so it hasn't hapoened yet.

You need to set the static instance in the constructor of your remote object. Doing it in the remote method may already be too late.

I suggest you also keep the Registry in a static variable server side. In fact strictly speaking that's the only reference you need to keep static.