Re: Help: argument type mismatch

When marshalling the arguments or result of a remote method
invocation, J2SE RMI (JRMP) automatically replaces JRMP-exported
remote objects with their corresponding remote stubs.[*]

Presumably you do indeed want your client to pass a remote reference
(stub) to the server, instead of passing (a copy of) the callback
remote object itself.

The "argument type mismatch" occurs because the stub class does not
extend the class Callback, your remote object's implementation class.
The stub class does implement the interface CallbackInterface, your
remote interface.  The solution is to change the parameter type of
ServerInterface's rmtRegisterClient method to be CallbackInterface
instead of Callback.

-- Peter

[*] java.rmi.MarshalledObject's constructor also does such
replacement.


> I've been trying to get a callback to work, but have never done so
> before.  I'm currently hungup by the following error in the
> following line.  I've created simplified files to try and isolate
> the problem.  Anyone know what causes this exception?

>   java.lang.IllegalArgumentException: argument type mismatch
>           at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
>           at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
>           at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
>           at java.lang.reflect.Method.invoke(Unknown Source)
>           at sun.rmi.server.UnicastServerRef.dispatch(Unknown Source)
>           at sun.rmi.transport.Transport$1.run(Unknown Source)
>           at java.security.AccessController.doPrivileged(Native Method)
>           at sun.rmi.transport.Transport.serviceCall(Unknown Source)
>           at sun.rmi.transport.tcp.TCPTransport.handleMessages(Unknown Source)
>           at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(Unknown 
> Source)
>           at java.lang.Thread.run(Unknown Source)
>           at 
> sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(Unknown Source)
>           at sun.rmi.transport.StreamRemoteCall.executeCall(Unknown Source)
>           at sun.rmi.server.UnicastRef.invoke(Unknown Source)
>           at Server_Stub.rmtRegisterClient(Unknown Source)
>           at Client.CallTheServer(Client.java:41)
>           at Client.run(Client.java:21)
>           at Client.main(Client.java:28)

>   public class Callback extends UnicastRemoteObject implements 
> CallbackInterface {
>        public int rmtFinalizeMove() throws RemoteException {
>             int l_nMyInt = 1;
>             return l_nMyInt;
>        }
>
>        public int rmtSayHi() throws RemoteException {
>             int l_nSuccess = 0;
>             System.out.println("rmtSayHi has been called!");
>             return l_nSuccess;
>        }
>
>        public Callback() throws RemoteException {
>        }
>   }

> public interface CallbackInterface extends Remote {
>       public int rmtFinalizeMove() throws RemoteException;
>       public int rmtSayHi() throws RemoteException;
> }

>   import java.rmi.*;
>   import java.util.Vector;
>
>   public interface ServerInterface extends Remote {
>     public String rmtMakeMove() throws RemoteException;
>     public int rmtRegisterClient( Callback p_cCallback ) throws 
> RemoteException;
>   }

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