Remotely loaded code

Question

Hi
I have a very simple example (the well known "Echo" example) that works fine if the client side can reach the stub class, so the stub class is in the clients classpath. If this is not the case, the stub class is not (directly) reachable to the client then I try, for example, downloading it from my Tomcat server. So I have all my server-side classes (interface, servant, server, stub) in the following directory:
"c:\jakarta-tomcat-4.1.18-LE-jdk14\webapps\ROOT\server\"
and all my client classes (interface, client) and the java.policy file in the following directory:
"f:\client"
I set the the SecurityManager in the Client class like this:
System.setSecurityManager(new SecurityManager()); write after the main statment. The java.policy looks like this:
grant {
    permission java.security.AllPermission;
}; The rest is the same as in the case in which I have all the classes in one directory, case in which everything works well.
I start the Tomcat server, compile all the classes, start the rmiregistry, run the server class like this:
java -Djava.rmi.server.codebase=http://localhost:90/server EchoServerand run the client:
java -Djava.security.policy=java.policy EchoClient localhost ... After this I get the following error:
java.rmi.UnmarshalException: error unmarshaling return; nested exception in:
              java.lang.ClassNotFoundException: EchoImpl_Stub ...I read that the classpath must be empty when calling the rmiregistry because if it can find the classes it needs from the class path, instead of using the server suplied URL, the URL system ceases to work.A client cannot get the class using the URL anymore. (SUN - SL-301).I don't know exactly if the variable CLASSPATH from my XP should be empty, or if I just set the classpath rigth before I start the rmiregistry like this:
set CLASSPATH =. and the start the registry (I have tried this and it still doesn't work).
How can I solve this? Any help would be greatly appreciated.
Regrads

Answer 1

Well EJP, I definitely think that the registry is finding the stub class from the classpath and therefor the client cannot use the URL provided by the server. I have no idee how to fix that. I start the rmiregistry from my EchoServer class, exactly after the main clause like I wrote in one of my previous posts, but that doesn't seem to help.
I am doing all this from one computer, so one single JVM. I have java.policy set on both client and server classes. My policy file is simple: grant {
    permission java.security.AllPermission;
}; and one copy is in the client directory and the other copy is in the server directory.
The problem is that if I start the registry from the command line from some place that it cannot find the stub class, then when I run the server I get that error:
...\jakarta-tomcat-4.1.18-LE-jdk14\webapps\ROOT\server>java -Djava.s
ecurity.policy=java.policy -Djava.rmi.server.codebase=http://localhost:90/server
EchoServer
Exception in thread "main" java.rmi.ServerException: RemoteException occurred in
server thread; nested exception is:
        java.rmi.UnmarshalException: error unmarshalling arguments; nested excep
tion is:
        java.lang.ClassNotFoundException: EchoImpl_Stub
        at sun.rmi.server.UnicastServerRef.oldDispatch(UnicastServerRef.java:385
        at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:240)
        at sun.rmi.transport.Transport$1.run(Transport.java:153)
        at java.security.AccessController.doPrivileged(Native Method)
        at sun.rmi.transport.Transport.serviceCall(Transport.java:149)
        at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:4
60)
        at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport
.java:701)
        at java.lang.Thread.run(Thread.java:595)
        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.rebind(Unknown Source)
        at java.rmi.Naming.rebind(Unknown Source)
        at EchoServer.main(EchoServer.java:11)
Caused by: java.rmi.UnmarshalException: error unmarshalling arguments; nested ex
ception is:
        java.lang.ClassNotFoundException: EchoImpl_Stub
        at sun.rmi.registry.RegistryImpl_Skel.dispatch(Unknown Source)
        at sun.rmi.server.UnicastServerRef.oldDispatch(UnicastServerRef.java:375
        at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:240)
        at sun.rmi.transport.Transport$1.run(Transport.java:153)
        at java.security.AccessController.doPrivileged(Native Method)
        at sun.rmi.transport.Transport.serviceCall(Transport.java:149)
        at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:4
60)
        at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport
.java:701)
        at java.lang.Thread.run(Thread.java:595)
Caused by: java.lang.ClassNotFoundException: EchoImpl_Stub
        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:306)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
        at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319)
        at java.lang.Class.forName0(Native Method)
        at java.lang.Class.forName(Class.java:242)
        at sun.rmi.server.LoaderHandler.loadClass(LoaderHandler.java:430)
        at sun.rmi.server.LoaderHandler.loadClass(LoaderHandler.java:165)
        at java.rmi.server.RMIClassLoader$2.loadClass(RMIClassLoader.java:620)
        at java.rmi.server.RMIClassLoader.loadClass(RMIClassLoader.java:247)
        at sun.rmi.server.MarshalInputStream.resolveClass(MarshalInputStream.jav
a:197)
        at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:153
8)
        at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1460)
        at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1
693)
        at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1299)
        at java.io.ObjectInputStream.readObject(ObjectInputStream.java:339)
        ... 9 moreSo no matter what I do, the server or the client can't seem to find the stub class. So I have no idea where to start the rmiregistry from.
Any suggestions on how to solve this problem?
Best regards,
Michael