Name: jk109818 Date: 07/14/2000


java version "1.2.2"
Classic VM (build JDK-1.2.2_005, native threads, symcjit)


I am trying to get a simple distributed program to work using RMI. I am
seeing the following exception on the client side while trying to make a
remote call:

RMIClient exception: RemoteException occurred in server thread; nested
exception is:
        java.rmi.UnmarshalException: error unmarshalling arguments; nested
exception is:
        java.lang.ClassNotFoundException: [Ljava.lang.Object;
java.rmi.ServerException: RemoteException occurred in server thread; nested
exception is:
        java.rmi.UnmarshalException: error unmarshalling arguments; nested
exception is:
        java.lang.ClassNotFoundException: [Ljava.lang.Object;
java.rmi.UnmarshalException: error unmarshalling arguments; nested exception is:
        java.lang.ClassNotFoundException: [Ljava.lang.Object;
java.lang.ClassNotFoundException: [Ljava.lang.Object;
        at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer
(StreamRemoteCall.java:249)
        at sun.rmi.transport.StreamRemoteCall.executeCall
(StreamRemoteCall.java:224)
        at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:126)
        at sample.rmiserver.RMIServer_Stub.queueTask(Unknown Source)
        at sample.rmiclient.RMIClient.run(RMIClient.java:24)

The offending line of code is in the constructor of the class (i.e.,
Task.java) that I am passing to the remote object's method (i.e.,
queueTask()).

This exception, however, is thrown sporadically, at best. If I run the
client repeatedly, it will succeed 1 out of 7 (or 8) times, while the other
6 throw the above exception. I have even tried looping within the client,
while sleeping for a set interval, to no avail. I did find a "magic"
interval of > 43 seconds, by which I mean if I sleep for 44 seconds or
more, the call will succeed every time. This, of course, will not do. If,
however, I comment out the assignment of a new Vector in the Task
constructor, the code never throws the exception.

I have no clue as to why the exception occurs. I have looked through every
forum, newsgroups, developer sites that I can think of and NO ONE seems to
have come across an intermittent exception like this. In fact, as far as I
can tell, no one else has had any ClassNotFoundExceptions for any files
other than the stubs.

It has to do with java.util.Vector somehow. I also tried an array of
serializable objects with the same results. None of the members of Task
seem to throw this exception in the constructor, only Vector and array. I
also tried initializing it in the declaration, same problem.

Could someone please take the following code and try to reproduce the error
I am seeing?

Thank you in advance for your help.

Sincerely,
Ivan



///////////////////////////////////////////////////////////////////////////
// The Compiler.
///////////////////////////////////////////////////////////////////////////
java version "1.2.2"
Classic VM (build JDK-1.2.2_005, native threads, symcjit)


///////////////////////////////////////////////////////////////////////////
// The Server Operating System.
///////////////////////////////////////////////////////////////////////////
Microsoft Windows NT
version 4.00.1381


///////////////////////////////////////////////////////////////////////////
// The Client Operating System.
///////////////////////////////////////////////////////////////////////////
Microsoft Windows 2000 [Version 5.00.2195]



///////////////////////////////////////////////////////////////////////////
//
// The Client Files.
//
///////////////////////////////////////////////////////////////////////////

***************************************************************************
* Client java.policy.
***************************************************************************
grant {
  permission java.net.SocketPermission "*:1024-65535", "connect,resolve";
};


***************************************************************************
* RMIClient.java.
*
* This file extends Thread and calls the methods of the remote object in
* its run() method.
*
***************************************************************************
package sample.rmiclient;

import java.rmi.*;

import sample.rmiserver.TaskManager;
import sample.rmiserver.Task;
import java.util.Vector;

public class RMIClient extends Thread {
   private String m_strName = null;

   public RMIClient ( String p_strIP ) {
      this.m_strName = "//" + p_strIP + "/TaskManager";
      this.start();
   }

   public void run() {
      if ( System.getSecurityManager() == null ) {
         System.setSecurityManager( new RMISecurityManager() );
      }
      try {
         TaskManager tMgr = ( TaskManager ) Naming.lookup( this.m_strName );

         System.out.println( "tMgr.queueTask( new Task() ) returned " +
                             tMgr.queueTask( new Task() ) );
         System.out.println( "tMgr.deleteTask(178) returned " +
                             tMgr.deleteTask(178) );
         System.out.println( "tMgr.getTasks() returned " +
                             tMgr.getTasks( "allTasks" ).size() +
                             " reports." );

      } catch ( Exception e ) {
         System.err.println( "RMIClient exception: " + e.getMessage() );
         e.printStackTrace();
      }
   }
}


***************************************************************************
* TestRMIClient.java.
*
* This file instantiates the RMIClient thread, passing it the IP Address of
* the RMI server.
*
***************************************************************************
package sample.rmiclient;

public class TestRMIClient {
   public static void main( String args[] ) {
      if ( args.length != 1 ) {
         System.err.println( "Syntax Error! Correct usage:\n" +
                    " java ComputeReport [RMI Server IP Address]\n" );
      }

      RMIClient rmic = new RMIClient( args[0] );
   }
}





///////////////////////////////////////////////////////////////////////////
//
// The Server Files.
//
///////////////////////////////////////////////////////////////////////////

***************************************************************************
* The Server java.policy (located in lib).
***************************************************************************
grant {
  permission java.net.SocketPermission "*:1024-65535", "connect,accept";
  permission java.io.FilePermission "C:\\Code\\lib\\-", "read";
  permission
java.io.FilePermission "C:\\inetpub\\wwwroot\\public_dirs\\tasks", "read";
  permission java.io.FilePermission "C:\\inetpub\\wwwroot\\public_dirs\\tasks\\-
", "read,write,delete";
};


***************************************************************************
* TaskManager.java.
***************************************************************************
package sample.rmiserver;

import java.util.Vector;

import java.rmi.Remote;
import java.rmi.RemoteException;

public interface TaskManager extends Remote {
   public int queueTask( Task p_oTask ) throws java.rmi.RemoteException;
   public boolean deleteTask( int p_intId ) throws java.rmi.RemoteException;
   public Vector getTasks( String p_str ) throws java.rmi.RemoteException;
}


***************************************************************************
* RMIServer.java.
***************************************************************************
package sample.rmiserver;

import java.util.Vector;

import java.rmi.*;
import java.rmi.server.*;
import java.net.*;

public class RMIServer
   extends java.rmi.server.UnicastRemoteObject
   implements TaskManager
{
   private static RMIServer m_rmiServer = null;

   public RMIServer() throws java.rmi.RemoteException {
      super();
   }

   public static synchronized RMIServer getInstance() {
      if ( m_rmiServer == null ) {
         try {
            m_rmiServer = new RMIServer();

         } catch ( java.rmi.RemoteException re ) {
            m_rmiServer = null;
         }
      }
      return m_rmiServer;
   }

   public int queueTask( Task p_oTask ) {
      // Queue the task here...
      return 0;
   }

   public boolean deleteTask( int p_intId ) {
      // Delete the task here...
      return true;
   }

   public Vector getTasks( String p_str ) {
      // Retrieve the tasks here...
      return new Vector();
   }

   public static void main( String[] args ) throws java.lang.Exception {
      if ( System.getSecurityManager() == null ) {
         System.setSecurityManager( new RMISecurityManager() );
      }

      TaskManager rmiServer = RMIServer.getInstance();
      String name = "//" + args[0] + "/TaskManager";
      Naming.rebind( name, rmiServer );
      System.out.println( "RMIServer bound and ready for client requests..." );
   }
}


***************************************************************************
* Task.java
***************************************************************************
package sample.rmiserver;

import java.util.Date;
import java.util.Hashtable;
import java.util.Vector;
import java.util.Enumeration;

public class Task implements java.io.Serializable {
   private java.util.Vector m_vctr = null;
   private java.util.Hashtable m_hshTable = null;
   private int m_int = 0;
   private String m_str = null;
   private java.util.Date m_dtm = null;

   public Task() {
//If this line is commented, the exception is never thrown.
//If left uncommented, the exception is thrown sporadically (or within a
//certain, mysterious, "black box" timeout interval)
      this.m_vctr = new java.util.Vector();
      this.m_hshTable = new Hashtable();
      this.m_str = new String( "" );
      this.m_dtm = new java.util.Date();
      this.m_dtm.setTime( this.m_dtm.getTime() );
   }

   public java.util.Vector getVector() { return this.m_vctr; }
   public java.util.Hashtable getHashtable() { return this.m_hshTable; }
   public int getInt() { return this.m_int; }
   public String getString() { return this.m_str; }
   public java.util.Date getDate() { return this.m_dtm; }

   public void setVector( java.util.Vector p_vctr ) { this.m_vctr =
p_vctr; }
   public void setHashtable( java.util.Hashtable p_hshTable ) { this.m_hshTable
= p_hshTable; }
   public void setInt( int p_int ) { this.m_int =
p_int; }
   public void setString( String p_str ) { this.m_str =
p_str; }
   public void setDate( java.util.Date p_dtm ) { this.m_dtm =
p_dtm; }
   public void addVectorElement( String p_elem ) { this.m_vctr.add
( p_elem ); }
}





///////////////////////////////////////////////////////////////////////////
//
// The build.
//
// Starting from the client machine (drive M) will proceed to do the following:
//
///////////////////////////////////////////////////////////////////////////

***************************************************************************
* Set the classpath.
***************************************************************************
SET CLASSPATH=M:\;M:\code;

***************************************************************************
* Remove the old class files (redundant)
***************************************************************************
DEL M:\code\sample\rmiserver\*.class
DEL M:\code\sample\rmiclient\*.class

***************************************************************************
* Remove the old server jar file (redundant)
***************************************************************************
DEL L:\Code\lib\serverCode.jar

***************************************************************************
* Compile the server and client code
***************************************************************************
javac M:\code\sample\rmiserver\*.java
javac M:\code\sample\rmiclient\*.java

***************************************************************************
* Create the stubs to the server code
***************************************************************************
rmic -d M:\code sample.rmiserver.RMIServer

***************************************************************************
* Jar the server code and stubs for use on the server.
***************************************************************************
PUSHD M:\codejar cvf M:\code\sample\lib\serverCode.jar sample\rmiserver\RMIServer*.class
jar uvf M:\code\sample\lib\serverCode.jar sample\rmiserver\TaskManager.class
jar uvf M:\code\sample\lib\serverCode.jar sample\rmiserver\Task.class
POPD

***************************************************************************
* Copy the serverCode jar file to the server.
***************************************************************************
COPY M:\code\sample\lib\serverCode.jar L:\Code\lib





///////////////////////////////////////////////////////////////////////////
//
// Starting the server.
//
///////////////////////////////////////////////////////////////////////////

***************************************************************************
* Change directory to lib (could just set path and leave it at that)
***************************************************************************
CD C:\Code\lib

***************************************************************************
* Set classpath
***************************************************************************
SET CLASSPATH=.;C:\Code\lib\serverCode.jar;

***************************************************************************
* Start rmiregistry, specifying 1099 as the port on which to listen.
***************************************************************************
START rmiregistry 1099

***************************************************************************
* Start RMIServer, specifying 1099 as the port on which to bind.
***************************************************************************
java -Djava.rmi.server.codebase=file:///c:\Code\lib\-/
     -Djava.rmi.server.hostname=<<<server host name>>>
     -Djava.security.policy=C:\Code\lib\java.policy
     sample.rmiserver.RMIServer <<<server IP address>>> 1099





///////////////////////////////////////////////////////////////////////////
//
// Starting the client.
//
///////////////////////////////////////////////////////////////////////////

***************************************************************************
* Start TestRMIClient, specifying the server's IP Address.
***************************************************************************
java -Djava.rmi.server.codebase=file:///M:\code\-/
     -Djava.security.policy=java.policy
     sample.rmiclient.TestRMIClient <<<server IP Address>>>
(Review ID: 106735)
======================================================================