Getting ClassNotFoundException when trying to run simple java rmi

Question

I am new to java RMI and was trying to run sample java rmi program. But I am getting java.rmi.notboundexception . Below is my code.

server code

server.java 

import java.rmi.registry.Registry;
import java.rmi.registry.LocateRegistry;
import java.rmi.RemoteException;
import java.rmi.server.UnicastRemoteObject;

public class Server implements Hello {

public Server() {}

public String sayHello() {
return "Hello, world!";
}

public static void main(String args[]) {
Hello stub = null;
Registry registry = null;

try {
    Server obj = new Server();
    stub = (Hello) UnicastRemoteObject.exportObject(obj, 0);
    registry = LocateRegistry.getRegistry();
    registry.bind("Hello", stub);

    System.err.println("Server ready");
} catch (Exception e) {
    System.err.println("Server exception: " + e.toString());
    e.printStackTrace();

/*  Rewritten as per EJP's remarks 
    try{
// Line 66 , where the error is pointing 
    registry.unbind("Hello");
    registry.bind("Hello",stub);
        System.err.println("Server ready");
    }catch(Exception ee){
    System.err.println("Server exception: " + ee.toString());
        ee.printStackTrace();
    }
}
*/ 


}
}

client code client.java

import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;

public class Client {

private Client() {}

public static void main(String[] args) {

String host = (args.length < 1) ? null : args[0];
try {
    Registry registry = LocateRegistry.getRegistry(host);
    Hello stub = (Hello) registry.lookup("Hello");
    String response = stub.sayHello();
    System.out.println("response: " + response);
} catch (Exception e) {
    System.err.println("Client exception: " + e.toString());
    e.printStackTrace();
}
}
}

Interface code

Hello.java

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

public interface Hello extends Remote {
    String sayHello() throws RemoteException;
}

Steps followed

javac Server.java
javac Client.java
Start the Java RMI registry with below command

start rmiregistry

After these, when i run the server with java server command , I am getting below exception. Exception changed from the original post after implementing the changes mentioned by EJP.

C:\Users\hp\Desktop\NUS Modules\Distributed systems\Assignment1\HelloWorld\Hello
World\Server>java Server
Server exception: java.rmi.ServerException: RemoteException occurred in server t
hread; nested exception is:
    java.rmi.UnmarshalException: error unmarshalling arguments; nested excep
tion is:
    java.lang.ClassNotFoundException: Hello
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: Hello
    at sun.rmi.server.UnicastServerRef.oldDispatch(UnicastServerRef.java:420
)
    at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:268)
    at sun.rmi.transport.Transport$1.run(Transport.java:178)
    at sun.rmi.transport.Transport$1.run(Transport.java:175)
    at java.security.AccessController.doPrivileged(Native Method)
    at sun.rmi.transport.Transport.serviceCall(Transport.java:174)
    at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:5
57)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTranspor
t.java:812)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport
.java:671)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.
java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor
.java:617)
    at java.lang.Thread.run(Thread.java:745)
    at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(Stream
RemoteCall.java:276)
    at sun.rmi.transport.StreamRemoteCall.executeCall(StreamRemoteCall.java:
253)
    at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:379)
    at sun.rmi.registry.RegistryImpl_Stub.bind(Unknown Source)
    at Server.main(Server.java:61)
Caused by: java.rmi.UnmarshalException: error unmarshalling arguments; nested ex
ception is:
    java.lang.ClassNotFoundException: Hello
    at sun.rmi.registry.RegistryImpl_Skel.dispatch(Unknown Source)
    at sun.rmi.server.UnicastServerRef.oldDispatch(UnicastServerRef.java:410
)
    at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:268)
    at sun.rmi.transport.Transport$1.run(Transport.java:178)
    at sun.rmi.transport.Transport$1.run(Transport.java:175)
    at java.security.AccessController.doPrivileged(Native Method)
    at sun.rmi.transport.Transport.serviceCall(Transport.java:174)
    at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:5
57)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTranspor
t.java:812)
    at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport
.java:671)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.
java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor
.java:617)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.ClassNotFoundException: Hello
    at java.net.URLClassLoader$1.run(URLClassLoader.java:372)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:360)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    at sun.rmi.server.LoaderHandler$Loader.loadClass(LoaderHandler.java:1207
)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:340)
    at sun.rmi.server.LoaderHandler.loadClassForName(LoaderHandler.java:1221 
)
    at sun.rmi.server.LoaderHandler.loadProxyInterfaces(LoaderHandler.java:7
31)
    at sun.rmi.server.LoaderHandler.loadProxyClass(LoaderHandler.java:674)
    at sun.rmi.server.LoaderHandler.loadProxyClass(LoaderHandler.java:611)
    at java.rmi.server.RMIClassLoader$2.loadProxyClass(RMIClassLoader.java:6
46)
    at java.rmi.server.RMIClassLoader.loadProxyClass(RMIClassLoader.java:311
)
    at sun.rmi.server.MarshalInputStream.resolveProxyClass(MarshalInputStrea
m.java:255)
    at java.io.ObjectInputStream.readProxyDesc(ObjectInputStream.java:1559)
    at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1515)
    at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1
774)
    at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1351)
    at java.io.ObjectInputStream.readObject(ObjectInputStream.java:371)
    ... 13 more

Please help to solve this error . Anything wrong in the code or any firewall settings need to be done.

java version - 1.8 operating system - Windows 7

Ya I have added comment on line 66. It points to the below line registry.unbind("Hello"); — Prabhuraj, Aug 26 '14 at 03:44
Note that your original code was obscuring the real problem, by assuming it was a bind problem. It wasn't. Don't write code like that. — user207421, Aug 26 '14 at 06:13
Another advice: Do not catch a generic `Exception` only. Capture more granular first that the methods you use are likely to throw, going from most specific to more general. — PM 77-1, Aug 26 '14 at 15:22

score 0 · Answer 1 · answered Aug 26 '14 at 03:46

0

You're trying to unbind something that isn't there. Get rid of the unbind() call and change the following bind() call to rebind().

But I don't see the point of doing any of that in an exception handler. Instead you should be printing the actual exception, to see what it is, first of all.

answered Aug 26 '14 at 03:46

user207421

305,947
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483

I removed the code in the exception handler and instead i am printing the exception now. Could you please check the new exception and help me to resolve this. – Prabhuraj Aug 26 '14 at 06:11

Getting ClassNotFoundException when trying to run simple java rmi

1 Answers1