Java RMI NoClassDefFoundError for javax.json.JsonValue in Remote object

Question

Running into Exception caused during call to UnicastRemoteObject.exportObject().

javax.json.jar is on the classpath and is used in many other places in the application without any problems.

This part of the application worked fine until I added a method that returned a JsonValue to the remote object.

Any ideas?

java.rmi.ServerError: Error occurred in server thread; nested exception is: 
    java.lang.NoClassDefFoundError: javax/json/JsonValue
    at sun.rmi.server.UnicastServerRef.oldDispatch(UnicastServerRef.java:416)
    at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:267)
    at sun.rmi.transport.Transport$1.run(Transport.java:177)
    at sun.rmi.transport.Transport$1.run(Transport.java:174)
    at java.security.AccessController.doPrivileged(Native Method)
    at sun.rmi.transport.Transport.serviceCall(Transport.java:173)
    at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:556)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:811)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:670)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at java.lang.Thread.run(Thread.java:745)
    at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(StreamRemoteCall.java:275)
    at sun.rmi.transport.StreamRemoteCall.executeCall(StreamRemoteCall.java:252)
    at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:378)
    at sun.rmi.registry.RegistryImpl_Stub.bind(Unknown Source)

NOTE: I also tried running the rmiregistry with codebase pointed directly at the javax.json.jar but the exception remains

rmiregistry -J-Djava.rmi.server.codebase=file:///JarLibrary/javax.json.jar &

Answer 1

Running into Exception caused during call to UnicastRemoteObject.exportObject().

No you aren't. See the stack trace. It's happening in Registry.bind().

You need to run the server with the java.rmi.server.codebase property set, but a file:// codebase URL isn't going to work unless either all the clients are running in the server host, in which case you don't really need the codebase feature at all, or it points to a shared folder in a form that both the Registry and the clients can use. It's usually HTTP.

But I question whether you need the codebase feature at all. You just have to ensure that the relevant jar file is on the CLASSPATH of both the Registry and the clients. The simplest way to ensure that for the Registry is to use LocateRegistry.createRegistry() in the server JVM instead of the external rmiregistry program.

I'm also wondering why you're using JSON at all. RMI is built over Object Serialization. You don't need to add another serializer.