Khalil Hamani Khalil Hamani - 1 month ago 26
Java Question

Java RMI Client experienced ClassCastException

I'm having trouble connecting my RMI client to the server. So I have these classes/interfaces :

package application;

import java.sql.ResultSet;

public interface InterfaceRMI {

public void insererEtudiant(String requete);
public void supprimerEtudiant(String requete);
public ResultSet selectionnerEtudiant(String requete);
}


Server class :

package application;

import java.rmi.RemoteException;
import java.rmi.server.UnicastRemoteObject;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;

public class ServeurMySQL extends UnicastRemoteObject implements InterfaceRMI {

public int port;

public ServeurMySQL(int port) throws RemoteException {
this.port = port;
}


@Override
public void insererEtudiant(String requete) {
// Implementation for insertion
}

@Override
public void supprimerEtudiant(String requete) {
// Implementation for delete
}

@Override
public ResultSet selectionnerEtudiant(String requete) {
// Implementation for selection
}
}


Connection test class :

package application;

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

public class test {

public static void main(String[] args) {
try {
Registry r = LocateRegistry.getRegistry(1098);

InterfaceRMI serveur = (InterfaceRMI) (r.lookup("serveurMySQL"));

} catch (Exception e) {
e.printStackTrace();
}
}
}


When I replaced the line
InterfaceRMI serveur = (InterfaceRMI) (r.lookup("serveurMySQL"));
by
r.lookup("serveurMySQL");
I didn't get the Exception, I understood that the connection worked, and the problem was only the cast. But I don't know how to resolve it.

The exeption is as follows :

java.lang.ClassCastException: com.sun.proxy.$Proxy0 cannot be cast to application.InterfaceRMI
at application.test.main(test.java:13)


P.S: The RMI server is launched without any problem.

Answer

First:

 public interface InterfaceRMI 

has to be

 public interface InterfaceRMI extends Remote

Second:

every method in your InterfaceRMI must declare throws RemoteException