RMI classpath problem

Question

Hi folks,
Using this tutorial;
http://java.sun.com/j2se/1.5.0/docs/guide/rmi/hello/hello-world.html
I was able to get the example working when I had all of my classes in the same directory as I ran it. E.g.
$pwd
/home/jmcparla/RMI2/server
$ ls
Hello.class  Server.class
$rmiregistry 2000 &
$ java Server
Server ready
$ pwd
/home/jmcparla/RMI2/client
$ ls
Client.class  Hello.class
$ java Client
response: Hello, world!So I decided to bundle the code into two Jars, Server.jar (containing Hello.class and Server.class) and Client.jar (Hello.class and Client.class). However this time when I went to start the Server;
$ pwd
/home/jmcparla/RMI2
$ ls
Server.jar  bin  client  policy  server  src
$ rmiregistry 2000 &
[1] 2848
$ java -jar Server.jarI got these exceptions;
Server exception: java.rmi.ServerException: RemoteException occurred in server t
hread; nested exception is:
        java.rmi.UnmarshalException: error unmarshalling arguments; nested excep
tion is:
        java.lang.ClassNotFoundException: Hello
java.rmi.ServerException: RemoteException occurred in server thread; nested exce
ption is:
        java.rmi.UnmarshalException: error unmarshalling arguments; nested excep
tion is:
        java.lang.ClassNotFoundException: Hello
        at sun.rmi.server.UnicastServerRef.oldDispatch(UnicastServerRef.java:396
        at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:250)
        at sun.rmi.transport.Transport$1.run(Transport.java:159)
        at java.security.AccessController.doPrivileged(Native Method)
        at sun.rmi.transport.Transport.serviceCall(Transport.java:155)
        at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:5
35)
        at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTranspor
t.java:790)
        at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport
.java:649)
        at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExec
utor.java:886)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor
.java:908)
        at java.lang.Thread.run(Thread.java:619)
        at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(Unknow
n Source)
        at sun.rmi.transport.StreamRemoteCall.executeCall(Unknown Source)
        at sun.rmi.server.UnicastRef.invoke(Unknown Source)
        at sun.rmi.registry.RegistryImpl_Stub.bind(Unknown Source)
        at Server.main(Server.java:22)
Caused by: java.rmi.UnmarshalException: error unmarshalling arguments; nested ex
ception is:
        java.lang.ClassNotFoundException: Hello
        at sun.rmi.registry.RegistryImpl_Skel.dispatch(Unknown Source)
        at sun.rmi.server.UnicastServerRef.oldDispatch(UnicastServerRef.java:386
        at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:250)
        at sun.rmi.transport.Transport$1.run(Transport.java:159)
        at java.security.AccessController.doPrivileged(Native Method)
        at sun.rmi.transport.Transport.serviceCall(Transport.java:155)
        at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:5
35)
        at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTranspor
t.java:790)
        at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport
.java:649)
        at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExec
utor.java:886)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor
.java:908)
        at java.lang.Thread.run(Thread.java:619)
Caused by: java.lang.ClassNotFoundException: Hello
        at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:252)
        at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320)
        at java.lang.Class.forName0(Native Method)
        at java.lang.Class.forName(Class.java:247)
        at sun.rmi.server.LoaderHandler.loadProxyInterfaces(LoaderHandler.java:7
11)
        at sun.rmi.server.LoaderHandler.loadProxyClass(LoaderHandler.java:655)
        at sun.rmi.server.LoaderHandler.loadProxyClass(LoaderHandler.java:592)
        at java.rmi.server.RMIClassLoader$2.loadProxyClass(RMIClassLoader.java:6
28)
        at java.rmi.server.RMIClassLoader.loadProxyClass(RMIClassLoader.java:294
        at sun.rmi.server.MarshalInputStream.resolveProxyClass(MarshalInputStrea
m.java:238)
        at java.io.ObjectInputStream.readProxyDesc(ObjectInputStream.java:1531)
        at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1493)
        at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1
732)
        at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1329)
        at java.io.ObjectInputStream.readObject(ObjectInputStream.java:351)
        ... 12 moreIt seems to be that it cannot find the Hello class file but this is bundled in Server.jar. Putting Server.jar on the classpath makes no difference.
Any ideas?

Answer 1

Cheers, using createRegistry(int) did the trick (along with a few other bits and pieces).
For the sake of aiding others with this kind of problem here's what I did. Remember most of it came from the Sun Java 5 RMI tutorial (http://java.sun.com/j2se/1.5.0/docs/guide/rmi/hello/hello-world.html).
1. Download and compile SUN's class file server (http://java.sun.com/javase/technologies/core/basic/rmi/class-server.zip). You'll need this to serve up the classes. Place this in a different directory to the one your going to use for the RMI tutorial.
2. Download the source files for the tutorial.
3. Use this directory structure (relative to /home/<username>)
| RMI/
        | src/
              | example/
                            | hello/
        | bin/4. Change the server to the following. The main points to note are the registry is now created (rather than located) and the port number used.
package example.hello;
import java.rmi.registry.Registry;
import java.rmi.registry.LocateRegistry;
import java.rmi.RemoteException;
import java.rmi.server.UnicastRemoteObject;
public class Server implements Hello {
    public Server() {}
    public String sayHello() {
     return "Hello, world!";
    public static void main(String args[]) {
     try {
            System.out.println("Starting Server");
         Server obj = new Server();
         Registry registry = LocateRegistry.createRegistry(2000);
            System.out.println("Created registry");
         Hello stub = (Hello) UnicastRemoteObject.exportObject(obj, 0);
            System.out.println("Exported Server");
         // Bind the remote object's stub in the registry
         registry.rebind("Hello", stub);
            System.out.println("Bound Server to \"Hello\"");
         System.out.println("Server ready");
     } catch (Exception e) {
         System.err.println("Server exception: " + e.toString());
         e.printStackTrace();
}5. In the src dir compile with the following;
javac -d ../bin example/hello/*.java6. In the bin dir create the server jar with the following;
jar cvfe Server.jar example.hello.Server example/hello/Server* example/hello/Hello*7. In the bin dir create the client jar with the following;
jar cvfe Client.jar example.hello.Client example/hello/Client* example/hello/Hello*8. Move both Jars out of the bin directory to the parent one (e.g. /home/<username>RMI/) (to prevent the rmi registry / server using the current dir in the classpath if you've set it up that way).
9. Create the policy file in the RMI directory (see above directory structure);
grant codeBase * {
    permission java.security.AllPermission;
    permission java.net.SocketPermission "*", "accept, connect, listen, resolve";
};10. Start the class file server (read the notes that come with it) in its own directory. Note the port number used (different from RMI registry) and the Jar file on the end of the path.
java ClassFileServer 2001 /home/<username>/RMI/Server.jar11. If this has worked you should be able to visit the URL http://localhost:2001 and get a blank page (as opposed to a broken link notification).
12. Start the RMI server in the bin dir. Note the port is the same as the one used to launch the class file server.
java -Djava.security.policy=policy -Djava.rmi.codebase=http://localhost:2001/ -jar Server.jar13. You should see the following output;
Starting Server
Created registry
Exported Server
Bound Server to "Hello"
Server ready14. Start the client
java -jar Client.jar15. You should see the following output;
response: Hello, world!