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

Question

我正在使用Java RMI实现客户端/服务器应用程序，客户端和服务器位于同一项目中的不同程序包中（当然，它们在同一台计算机上运行），并且接口在“通用”程序包中定义。得到两个远程对象之一，我得到了上述例外。 我读过一些SO答案，人们建议将静态引用添加到远程对象，这样就永远无法收集它们，但这是行不通的！

这是客户端和服务器的代码

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（服务器端）

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（服务器主）

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;
    }

 }

每个接口都有@RMIMapping注释，该注释提供了对象绑定名称。 但我确定问题不会因此而来

对我来说，这真是个难题，这是stacktrace……非常感谢您的帮助！

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)

编辑：@EJP在此之前，我已经做了类似

public class RemoteObject implements IRemoteObject
{
    private static RemoteObject instance;

    public RemoteObject ()
    {
       instance = this;
    }

    public someType someMethod (...)
}

但是它抛出了同样的异常。 此外，如您所见，在scServerConfig中有一个公共的静态RMIServer服务器。

它封装了注册表参考。 如果我所做的这些事情是正确的，我认为添加静态引用可能还不够，即使艰难的“突然”也开始为我工作。 我错了吗？

Answer 1

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

没有添加。 您正在尝试调用添加它的远程方法。 您在那方面失败了，所以它还没有得到加强。

您需要在远程对象的构造函数中设置静态实例。 用远程方法执行此操作可能已经为时已晚。

我建议您也将注册表保留在静态变量服务器端。 实际上严格来说，这是您需要保持静态的唯一参考。