Why Do I Get \'java.rmi.ServerException: RemoteException Occurred in Server Thread (ClassNotFoundException)\' in My RMI Server?

"java.rmi.ServerException: RemoteException Occurred in Server Thread (ClassNotFoundException)"

Problem:

When attempting to start an RMI server, the following exception is encountered:

java.rmi.ServerException: RemoteException occurred in server thread; nested exception is:
        java.rmi.UnmarshalException: error unmarshalling arguments; nested exception is:
        java.lang.ClassNotFoundException: Interfaces.RemoteMethodIntf

Diagnosis:

The underlying issue is that the RMI Registry cannot find the class referenced in the remote interface. This can occur in several situations:

• Exporting: The stub generation tool (rmic) was not run or the necessary classpath modifications described in the preamble to the UnicastRemoteObject Javadoc were not performed.
• Binding: The Registry does not have the stub, remote interface, or their dependencies on its classpath.
• Looking Up: The client does not have the same classes on its classpath.
• Calling Remote Method: Either the client sent an object to the server of a class missing on its classpath, or the server returned an object of a class missing on the client's classpath.

Solution:

In this particular case, the problem pertains to the Registry missing the necessary classes on its classpath. To resolve this issue, there are several options:

• Start the Registry with a modified CLASSPATH that includes the relevant JARs or directories.
• Start the Registry using LocateRegistry.createRegistry() within the server's JVM.
• Utilize dynamic stubs as described in the UnicastRemoteObject Javadoc. However, this may require addressing dependency issues.
• Ensure that case (4) above does not occur by verifying classpath consistency for object transfer.
• Consider using the codebase feature, recognizing that this is a deployment option.

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