Question

I am getting an error when attempting to connect to an RMI service:

I am executing the client code using:

java -Djava.security.manager -Djava.security.policy=path\to\policy.all -jar "path\to\jarfile" "localhost:2020"

The code I am using is:

public class PowerServiceClient
{
    public static void main(String args[]) throws Exception
    {

         System.setSecurityManager
            (new RMISecurityManager());

         // Call registry for PowerService
         PowerService service = (PowerService) Naming.lookup
            ("rmi://localhost:2020/PowerService");

         DataInputStream din = new
             DataInputStream (System.in);

    }
}

The error I am receiving is:

    Exception in thread "main" java.rmi.UnmarshalException: 
    error unmarshalling return; nested exception is:

    java.lang.ClassNotFoundException: rmiservice.PowerService
    at sun.rmi.registry.RegistryImpl_Stub.lookup(Unknown Source)
    at java.rmi.Naming.lookup(Unknown Source)
    at powerclient.PowerServiceClient.main(PowerServiceClient.java:32)
    Caused by: java.lang.ClassNotFoundException: rmiservice.PowerService
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Unknown Source)
    at sun.rmi.server.LoaderHandler.loadProxyInterfaces(Unknown Source)
    at sun.rmi.server.LoaderHandler.loadProxyClass(Unknown Source)
    at sun.rmi.server.LoaderHandler.loadProxyClass(Unknown Source)
    at java.rmi.server.RMIClassLoader$2.loadProxyClass(Unknown Source)
    at java.rmi.server.RMIClassLoader.loadProxyClass(Unknown Source)
    at sun.rmi.server.MarshalInputStream.resolveProxyClass(Unknown Source)
    at java.io.ObjectInputStream.readProxyDesc(Unknown Source)
    at java.io.ObjectInputStream.readClassDesc(Unknown Source)
    at java.io.ObjectInputStream.readOrdinaryObject(Unknown Source)
    at java.io.ObjectInputStream.readObject0(Unknown Source)
    at java.io.ObjectInputStream.readObject(Unknown Source)
    ... 3 more

Does anyone know what the problem is here?

Answer 1

The Registry needs access to your remote interface class and its dependencies on its classpath. There are three solutions to that. In order of ease:

1. Start the Registry inside your server JVM, with LocateRegistry.createRegistry()
2. Start the rmiregistry process with a -D-Jclasspath= argument
3. Use the codebase feature.