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包中(当然它们在同一台机器上运行)，并且接口(interface)在“通用”包中定义。当我尝试获取两个远程对象之一，但出现上述异常。我读过一些 SO 答案，人们建议添加对远程对象的静态引用，以便永远不会收集它们，但这不起作用!

这是客户端和服务器的代码

通知服务代理

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;
    }
}

RMI客户端

    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(interface)都使用提供对象绑定(bind)名称的 @RMIMapping 注释进行注释。但我确信问题不是由此而来

这对我来说是一个真正的谜，这是堆栈跟踪......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，我做过类似的事情

public class RemoteObject implements IRemoteObject
{
    private static RemoteObject instance;

    public RemoteObject ()
    {
       instance = this;
    }

    public someType someMethod (...)
}

但它抛出了相同的异常。此外，如您所见，在 scServerConfig 中有一个 公共(public)静态RMIServer服务器；

它封装了注册表引用。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，甚至艰难的“突然”开始对我起作用。我错了吗？

Answer 1

java.rmi.NoSuchObjectException but static reference added

未添加。您正在尝试调用添加它的远程方法。你在这方面失败了，所以它还没有发生。

您需要在远程对象的构造函数中设置静态实例。在远程方法中执行此操作可能已经太晚了。

我建议您还将注册表保留在静态变量服务器端。事实上，严格来说，这是您需要保持静态的唯一引用。