java.rmi.NoSuchObjectException：没有这样的对象异常

Question

There have been acouple of questions about this already, but their answers suggest that the exported object has been GC'd on the server side and that is cousing the problems. However it seems like that this is not the issue here.

Mentioned exception is thrown only on single machine:

PRETTY_NAME="Debian GNU/Linux 8 (jessie)"
NAME="Debian GNU/Linux"
VERSION_ID="8"
VERSION="8 (jessie)"

With java:

java version "1.8.0_45"
Java(TM) SE Runtime Environment (build 1.8.0_45-b14)
Java HotSpot(TM) 64-Bit Server VM (build 25.45-b02, mixed mode)

This happend on the same machine with OpenJDK 7something as well.

According to other answers I am supposed to keep a strong reference to handling objects. I am doing it now, so what more can be done?

The same code works on windows as well as on a different remote linux machine with java 7. Any ideas why?

I have implemented some finalizers to the connected classes, but none of them are called.

As suggested I am using static references. As for me there is no way get exported object GC enligible. Exception is thrown on remote method invocation right after object lookup.

Piece of class

public class Client{
     //some fields
    private final int RMI_PORT;
    private static SearchTestServiceImpl searchTestService;
    private static Remote stub;
    private Registry registry;
    //and starting service
    public void startService() throws RemoteException {
        createRegistry();
        searchTestService = new SearchTestServiceImpl(name);
        stub = UnicastRemoteObject.exportObject(searchTestService, RMI_PORT + 1);
        registry.rebind(SearchTestService.class.getName(), stub);
        log.info("Binding {} to port {}", SearchTestService.class.getName(), RMI_PORT + 1);
    }

    private void createRegistry() throws RemoteException {
        log.info("Starting RMI registry on port {}", RMI_PORT);
        registry = LocateRegistry.createRegistry(RMI_PORT);
        }

(...)
    }

And bootstrapping code

public class Bootstrap {

    private Logger log = LoggerFactory.getLogger(Bootstrap.class);
    private static Client c;

    public static void main(String[] args) throws NumberFormatException, 
// some preparations
        c = new Client(Integer.valueOf(port), name);
        c.startService();
        System.gc();
        System.runFinalization();
        synchronized (c) {
            c.wait();
        }

    }
}

and stacktrace

java.rmi.NoSuchObjectException: no such object in table
    at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(Unknown Source) ~[na:1.7.0_65]
    at sun.rmi.transport.StreamRemoteCall.executeCall(Unknown Source) ~[na:1.7.0_65]
    at sun.rmi.server.UnicastRef.invoke(Unknown Source) ~[na:1.7.0_65]
    at java.rmi.server.RemoteObjectInvocationHandler.invokeRemoteMethod(Unknown Source) ~[na:1.7.0_65]
    at java.rmi.server.RemoteObjectInvocationHandler.invoke(Unknown Source) ~[na:1.7.0_65]
    at com.sun.proxy.$Proxy0.getName(Unknown Source) ~[na:na]
    at call to a method of remote lookedup object #getName in this example.

Requested piece of code - lookup and call that throws exception

//somewhere

SearchTestService c = getClient(address); // this returns nice stub
String name = c.getName(); // this is throwing exception

private SearchTestService getClient(String string) throws NumberFormatException, RemoteException, NotBoundException {
    String[] parts = string.split(":");
    Registry registry = LocateRegistry.getRegistry(parts[0], Integer.parseInt(parts[1]));
    SearchTestService client = (SearchTestService) registry.lookup(SearchTestService.class.getName());
    return (SearchTestService) client;
}

Console output after running "listening" client side code (with RMI registry)

10:17:55.915 [main] INFO  pl.breeze.searchtest.client.Client - Starting RMI registry on port 12097
10:17:55.936 [main] INFO  p.b.s.client.SearchTestServiceImpl - Test agent Breeze Dev staging is up and running
10:17:55.952 [main] INFO  pl.breeze.searchtest.client.Client - Binding pl.choina.searchtest.remote.SearchTestService to port 12098

And this waits untill manuall shutdown - tested.

Answer 1

NoSuchObjectException

Javadoc :

A NoSuchObjectException is thrown if an attempt is made to invoke a method on an object that no longer exists in the remote virtual machine.

This means that the remote object referred to by the stub you are calling methods on has been unexported, ie the stub is 'stale'. The only way that can happen is by unexporting the object, either manually or as a result of GC.

As suggested I am using static references.

No you're not. You need to make the Registry reference static. Otherwise you just form a cycle between Client and Registry that can be garbage-collected all at once.

Why you're calling your server Client is another mystery.

EDIT A few comments:

stub = UnicastRemoteObject.exportObject(searchTestService, RMI_PORT + 1);

There's no need to use a second port here. Just re-use the Registry port.

log.info("Binding {} to port {}", SearchTestService.class.getName(), RMI_PORT + 1);

This is misleading. You've already done both, but what you have done is:

1. Exported the object on the port, and
2. Bound the object to a name

in two separate steps.

System.gc();
System.runFinalization();

Strange things to be doing here, or indeed anywhere.

synchronized (c) {
    c.wait();
}

This isn't reliable. You don't really need anything here, as RMI should keep the JVM open as long as it has exported remote objects, but you could do what the Registry does:

while (true)
{
    Thread.sleep(Integer.MAX_VALUE);
}

with the appropriate exception handling.

I can't reproduce your problem, but then I'm on Windows 7.