RMI：ServerException、RemoteException、UnmarshalException、UnmarshalException

Question

I followed this tutorial: https://docs.oracle.com/javase/6/docs/technotes/guides/rmi/hello/hello-world.html#5

I compiled them at command prompt and after that I started rmiregistry. Then, after I typed:

    start java -classpath "." example.Server

it didn't show "Server ready." But, it didn't display any errors as well.

While when I tried it at Eclipse, it showed this:

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

Hello.java

   package example;

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

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

Server.java

    package example;

    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[]) {

    try {
        Server obj = new Server();
        Hello stub = (Hello) UnicastRemoteObject.exportObject(obj, 0);

        // Bind the remote object's stub in the registry
        Registry registry = LocateRegistry.getRegistry();
        registry.bind("Hello", stub);

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

}

Client.java

   package example;

   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();
            }
      }
   }

Are there any steps that I missed? What should I do?

Answer 1

ClassNotFoundException: example.Hello - your application does not find this class. Add this class to the class path, both to the client and to the server.

If you launch your client on some other PC than Sserver, don't forget to copy your class example.Hello together with your client.