ClassNotFound when loading code to server

Question

Hi all!
I'm fairly new to RMI but I've managed to get my RMI application running. However, when I come to the good stuff it all brakes down. I've written a simple service (Hello world) that shall be downloaded to the server. The code below is deploying this service from the client:
package jflex.rmi;
import java.rmi.Naming;
import jflexserver.services.*;
import jflex.rmi.TestTask;
public class ServerComm implements java.io.Serializable {
     Object message = "blanc";
     TestTask testTask = new TestTask();
     // "obj" is the identifier that we'll use to refer
     // to the remote object that implements the "Hello"
     // interface
     JFlexService obj = null;
     public void handShake() {
          try {
               System.out.println("Loading policy file...");
               System.setProperty("java.security.policy", "file:///C:\\JFlex\\Java\\jflexpolicy");
               System.setProperty("java.rmi.server.codebase","file:///c:\\JFlex\\Java\\jflex/");
               //System.out.println("Trying to increase timeout to 30 sec");
               //System.setProperty("sun.rmi.transport.connectionTimeout", "30000");
               System.out.println("Trying to lookup JFlexService...");
               obj = (JFlexService)Naming.lookup("//tomcat/JFlexServer");
               System.out.println("Trying to execute service TestTask...");
               System.out.println(obj.toString());
               message = obj.runService(testTask);
          } catch (Exception e) {
               e.printStackTrace();
}This will give the following exception:
Loading policy file...
Trying to lookup JFlexService...
Trying to execute service TestTask...
jflexserver.JFlexServer_Stub[RemoteStub [ref: [endpoint:[192.168.0.3:2770](remot
e),objID:[1f1fba0:f6cc1ac17b:-8000, 0]]]]
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: jflex.rmi.TestTask
at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:292)
at sun.rmi.transport.Transport$1.run(Transport.java:148)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.Transport.serviceCall(Transport.java:144)
at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:4
60)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport
.java:701)
at java.lang.Thread.run(Thread.java:536)
at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(Stream
RemoteCall.java:247)
at sun.rmi.transport.StreamRemoteCall.executeCall(StreamRemoteCall.java:
223)
at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:133)
at jflexserver.JFlexServer_Stub.runService(Unknown Source)
at jflex.rmi.ServerComm.handShake(ServerComm.java:30)
at jflex.JFlexFrame.<init>(JFlexFrame.java:218)
at jflex.JFlex.main(JFlex.java:23)
Caused by: java.rmi.UnmarshalException: error unmarshalling arguments; nested ex
ception is:
java.lang.ClassNotFoundException: jflex.rmi.TestTask
at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:252)
at sun.rmi.transport.Transport$1.run(Transport.java:148)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.Transport.serviceCall(Transport.java:144)
at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:4
60)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport
.java:701)
at java.lang.Thread.run(Thread.java:536)
Caused by: java.lang.ClassNotFoundException: jflex.rmi.TestTask
at java.net.URLClassLoader$1.run(URLClassLoader.java:198)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:186)
at java.lang.ClassLoader.loadClass(ClassLoader.java:299)
at java.lang.ClassLoader.loadClass(ClassLoader.java:255)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:315)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:217)
at sun.rmi.server.LoaderHandler.loadClass(LoaderHandler.java:427)
at sun.rmi.server.LoaderHandler.loadClass(LoaderHandler.java:159)
at java.rmi.server.RMIClassLoader$2.loadClass(RMIClassLoader.java:631)
at java.rmi.server.RMIClassLoader.loadClass(RMIClassLoader.java:257)
at sun.rmi.server.MarshalInputStream.resolveClass(MarshalInputStream.jav
a:200)
at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:151
3)
at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1435)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1
626)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1274)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:324)
at sun.rmi.server.UnicastRef.unmarshalValue(UnicastRef.java:297)
at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:246)
... 6 more
Whu on earth can't the server locate this package. The point of RMI is that the server CAN be unaware of the code downloaded to its JVM, right???
Thanks in advance!

Answer 1

Thanks for helping me! I'm starting the rmiregistry in
a clean environment (according to the Sun tutorial)
by:
set CLASSPATH=; //Just to make sure all paths are
viped out
rmiregistry -J-Dsun.rmi.loader.logLevel=VERBOSE
If I echo the current CLASSPATH, I can see it's empty.
However, I'm starting the registry in the root
directory of the RMI-server application. Bad idea? As
I understand it, the registry shall be started in an
environment without any references to stub-files or
anything else involving the RMI-server. Still
confused...Looking at your explanation you could run it in two ways
1) Run it in an environrmrnt where classpath is not null and where the java.rmi.codebase property is set appropriately.
2) Run it in an environment where the applications classes are not on the classpath.
The requirements for 2) are
a) CLASSPATH is not null and doesnot include any entry of the your application classes.
b) CLASSPATH is null and working directory (".") is not the root your applications packages structure. The reason being that the null CLASSPATH is interpreted as "."
Or else in case you dont wanna set the codebase property u can acquire a required class via RMIClassLoader.loadClass method.