UnmarshalException and ClassNotFoundException: what am I doing wrong?

Question

This is first time that I use RMI, and this the main that I wrote:

public class Main {
    public static void main(String[] args)
    {
        try {
            String name = "Server";
            ServerInterface server = new ServerRMI(0,new Executor());
            ServerInterface stub =
                    (ServerInterface) UnicastRemoteObject.exportObject(server, 0);
            Registry registry = LocateRegistry.getRegistry();
            registry.rebind(name, stub);
            System.out.println("ServerRMI bound");
        } catch (Exception e) {
            System.err.println("ServerRMI exception:");
            e.printStackTrace();
        }
    }
}

I already read this post where it is suggested to modify the codebase, so I set the VM options of Intellij as: -Djava.rmi.server.codebase=file:/home/luca/Documents/PAD/RaftFS/target/ Where target contains RaftFS-1.0-SNAPSHOT.jar which is the jar produced by Maven (and so containing ServerInterface ). Obviously, before lunch the Main program I execute rmiregistry on the shell. The CLASSHPATH variable is not set in my system environment.

Anyway these exception raise when I execute this program:

/usr/lib/jvm/java-1.7.0-openjdk-amd64/bin/java -Djava.rmi.server.codebase=file:/home/luca/Documents/PAD/RaftFS/target/ -Didea.launcher.port=7535 -Didea.launcher.bin.path=/home/luca/idea-IU-139.1117.1/bin -Dfile.encoding=UTF-8 -classpath /usr/lib/jvm/java-1.7.0-openjdk-amd64/jre/lib/compilefontconfig.jar:/usr/lib/jvm/java-1.7.0-openjdk-amd64/jre/lib/rt.jar:/usr/lib/jvm/java-1.7.0-openjdk-amd64/jre/lib/charsets.jar:/usr/lib/jvm/java-1.7.0-openjdk-amd64/jre/lib/rhino.jar:/usr/lib/jvm/java-1.7.0-openjdk-amd64/jre/lib/jsse.jar:/usr/lib/jvm/java-1.7.0-openjdk-amd64/jre/lib/jce.jar:/usr/lib/jvm/java-1.7.0-openjdk-amd64/jre/lib/resources.jar:/usr/lib/jvm/java-1.7.0-openjdk-amd64/jre/lib/management-agent.jar:/usr/lib/jvm/java-1.7.0-openjdk-amd64/jre/lib/javazic.jar:/usr/lib/jvm/java-1.7.0-openjdk-amd64/jre/lib/ext/sunjce_provider.jar:/usr/lib/jvm/java-1.7.0-openjdk-amd64/jre/lib/ext/dnsns.jar:/usr/lib/jvm/java-1.7.0-openjdk-amd64/jre/lib/ext/icedtea-sound.jar:/usr/lib/jvm/java-1.7.0-openjdk-amd64/jre/lib/ext/sunpkcs11.jar:/usr/lib/jvm/java-1.7.0-openjdk-amd64/jre/lib/ext/java-atk-wrapper.jar:/usr/lib/jvm/java-1.7.0-openjdk-amd64/jre/lib/ext/zipfs.jar:/usr/lib/jvm/java-1.7.0-openjdk-amd64/jre/lib/ext/localedata.jar:/home/luca/Documents/PAD/RaftFS/out/production/main:/home/luca/idea-IU-139.1117.1/lib/idea_rt.jar com.intellij.rt.execution.application.AppMain PAD.RaftFS.Server.Main
ServerRMI exception:
java.rmi.ServerException: RemoteException occurred in server thread; nested exception is: 
    java.rmi.UnmarshalException: error unmarshalling arguments; nested exception is: 
    java.lang.ClassNotFoundException: PAD.RaftFS.Server.ServerInterface
    at sun.rmi.server.UnicastServerRef.oldDispatch(UnicastServerRef.java:419)
    at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:267)
    at sun.rmi.transport.Transport$2.run(Transport.java:202)
    at sun.rmi.transport.Transport$2.run(Transport.java:199)
    at java.security.AccessController.doPrivileged(Native Method)
    at sun.rmi.transport.Transport.serviceCall(Transport.java:198)
    at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:567)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:828)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.access$400(TCPTransport.java:619)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler$1.run(TCPTransport.java:684)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler$1.run(TCPTransport.java:681)
    at java.security.AccessController.doPrivileged(Native Method)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:681)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at java.lang.Thread.run(Thread.java:745)
    at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(StreamRemoteCall.java:275)
    at sun.rmi.transport.StreamRemoteCall.executeCall(StreamRemoteCall.java:252)
    at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:378)
    at sun.rmi.registry.RegistryImpl_Stub.rebind(Unknown Source)
    at PAD.RaftFS.Server.Main.main(Main.java:20)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:134)
Caused by: java.rmi.UnmarshalException: error unmarshalling arguments; nested exception is: 
    java.lang.ClassNotFoundException: PAD.RaftFS.Server.ServerInterface
    at sun.rmi.registry.RegistryImpl_Skel.dispatch(Unknown Source)
    at sun.rmi.server.UnicastServerRef.oldDispatch(UnicastServerRef.java:409)
    at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:267)
    at sun.rmi.transport.Transport$2.run(Transport.java:202)
    at sun.rmi.transport.Transport$2.run(Transport.java:199)
    at java.security.AccessController.doPrivileged(Native Method)
    at sun.rmi.transport.Transport.serviceCall(Transport.java:198)
    at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:567)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:828)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.access$400(TCPTransport.java:619)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler$1.run(TCPTransport.java:684)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler$1.run(TCPTransport.java:681)
    at java.security.AccessController.doPrivileged(Native Method)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:681)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.ClassNotFoundException: PAD.RaftFS.Server.ServerInterface
    at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
    at sun.rmi.server.LoaderHandler$Loader.loadClass(LoaderHandler.java:1206)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:274)
    at sun.rmi.server.LoaderHandler.loadClassForName(LoaderHandler.java:1219)
    at sun.rmi.server.LoaderHandler.loadProxyInterfaces(LoaderHandler.java:729)
    at sun.rmi.server.LoaderHandler.loadProxyClass(LoaderHandler.java:673)
    at sun.rmi.server.LoaderHandler.loadProxyClass(LoaderHandler.java:610)
    at java.rmi.server.RMIClassLoader$2.loadProxyClass(RMIClassLoader.java:646)
    at java.rmi.server.RMIClassLoader.loadProxyClass(RMIClassLoader.java:311)
    at sun.rmi.server.MarshalInputStream.resolveProxyClass(MarshalInputStream.java:255)
    at java.io.ObjectInputStream.readProxyDesc(ObjectInputStream.java:1558)
    at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1514)
    at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1771)
    at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1350)
    at java.io.ObjectInputStream.readObject(ObjectInputStream.java:370)
    ... 17 more

IMPORTANT UPDATE: if substitute Registry registry = LocateRegistry.getRegistry(); with Registry registry = LocateRegistry.createRegistry(1099); and avoiding to execute rmiregistry , then no exception is raised. Can I assume that with 0 parameter the register is bounded to an anonymous port? Why this happens? It actually solve the problem or not?

Answer 1

To answer your actual question, the Registry didn't have the class mentioned available on its CLASSPATH. Using the codebase feature is one solution to that, but it's complex. A simpler solution is to start the registry in the server JVM with LocateRegistry.createRegistry().

You can use port zero for that, which does indeed indicate an anonymous port, but it's completely pointless to do so. It has no bearing on the original problem and it just makes your Registry impossible for the client to find.

Another solution is to specifics the CLASSPATH when starting the registry, with

rmiregistry -J-classpath=...