Problema con gli Ejb

[tulipan]

Ho trovato il seguente codice:

import java.util.Collection;
import javax.naming.InitialContext;
import javax.naming.NamingException;
import ejb.session.stateful.ShoppingCart;


public class Client {
    
	public static void main(String[] args) throws Exception {
		ejb.session.stateful.ShoppingCart shoppingCart=null;
		try {
            InitialContext ic = new InitialContext();
            shoppingCart = (ShoppingCart) ic.lookup("ejb.session.stateful.ShoppingCart");
            
        } catch (NamingException ex) {
            ex.printStackTrace();
        }
		shoppingCart.addItem("Bread");
		shoppingCart.addItem("Milk");
		System.out.println("Contents of your cart are: ");
		Collection<String> items=shoppingCart.getItems();
		for(String item :items){
			System.out.println(item);
			
		}
		shoppingCart.finished();
	}


}

ma ottengo il seguente errore:
javax.naming.NoInitialContextException: Need to specify class name in environment or system property, or as an applet parameter, or in an application resource file: java.naming.factory.initial