ho risolto l'errore, il problema era nel client. L'ho modificato in questo modo

ProvaEjb.java
codice:
public class ProvaEjb {

	
	public static void main(String[] args) {
		
		InitialContext ctx = null;
		
		try {
//		    Hashtable env = new Hashtable();
//		    env.put(Context.INITIAL_CONTEXT_FACTORY, "weblogic.jndi.WLInitialContextFactory");
//		    env.put(Context.PROVIDER_URL, "t3://localhost:7001");
//		    env.put(Context.SECURITY_PRINCIPAL, "giuseppe");
//		    env.put(Context.SECURITY_CREDENTIALS, "giuseppe");
		    
		    
		    //ctx = new InitialContext();
		    //ctx.
		    
		    //ctx = new InitialContext(env);
		    ctx = new InitialContext();
		    ctx.addToEnvironment(Context.INITIAL_CONTEXT_FACTORY, "weblogic.jndi.WLInitialContextFactory");
		    ctx.addToEnvironment(Context.PROVIDER_URL, "t3://localhost:7001");
		    ctx.addToEnvironment(Context.SECURITY_PRINCIPAL, "giuseppe");
		    ctx.addToEnvironment(Context.SECURITY_CREDENTIALS, "giuseppe");
		    
		    
		    
		    
		}catch (NamingException e) {
		    e.printStackTrace();
		}
		
		
		try {
		    Object obj = ctx.lookup("AdderBean");
		    
			if ( obj != null ){
				AdderHome home = (AdderHome)PortableRemoteObject.narrow(obj, AdderHome.class);
				Adder adder = home.create();
				System.out.println(adder.add(2, 5));
			}
			
		    
		}catch (Exception e) {
		    e.printStackTrace();
		}
		
		
		
		
	}
	
}
adesso però quando faccio girare il client ProvaEjb.java ottengo quest'altro tipo di errore:
codice:
javax.naming.NameNotFoundException: Unable to resolve 'AdderBean'. Resolved '' [Root exception is javax.naming.NameNotFoundException: Unable to resolve 'AdderBean'. Resolved '']; remaining name 'AdderBean'
	at weblogic.rjvm.ResponseImpl.unmarshalReturn(ResponseImpl.java:221)
	at weblogic.rmi.cluster.ClusterableRemoteRef.invoke(ClusterableRemoteRef.java:338)
	at weblogic.rmi.cluster.ClusterableRemoteRef.invoke(ClusterableRemoteRef.java:252)
	at weblogic.jndi.internal.ServerNamingNode_1001_WLStub.lookup(Unknown Source)
	at weblogic.jndi.internal.WLContextImpl.lookup(WLContextImpl.java:379)
	at weblogic.jndi.internal.WLContextImpl.lookup(WLContextImpl.java:367)
	at javax.naming.InitialContext.lookup(Unknown Source)
	at it.ejb.session.ProvaEjb.main(ProvaEjb.java:46)
Caused by: javax.naming.NameNotFoundException: Unable to resolve 'AdderBean'. Resolved ''
	at weblogic.jndi.internal.BasicNamingNode.newNameNotFoundException(BasicNamingNode.java:1138)
	at weblogic.jndi.internal.BasicNamingNode.lookupHere(BasicNamingNode.java:251)
	at weblogic.jndi.internal.ServerNamingNode.lookupHere(ServerNamingNode.java:171)
	at weblogic.jndi.internal.BasicNamingNode.lookup(BasicNamingNode.java:205)
	at weblogic.jndi.internal.RootNamingNode_WLSkel.invoke(Unknown Source)
	at weblogic.rmi.internal.BasicServerRef.invoke(BasicServerRef.java:589)
	at weblogic.rmi.cluster.ClusterableServerRef.invoke(ClusterableServerRef.java:224)
	at weblogic.rmi.internal.BasicServerRef$1.run(BasicServerRef.java:479)
	at weblogic.security.acl.internal.AuthenticatedSubject.doAs(AuthenticatedSubject.java:363)
	at weblogic.security.service.SecurityManager.runAs(Unknown Source)
	at weblogic.rmi.internal.BasicServerRef.handleRequest(BasicServerRef.java:475)
	at weblogic.rmi.internal.BasicServerRef.access$300(BasicServerRef.java:59)
	at weblogic.rmi.internal.BasicServerRef$BasicExecuteRequest.run(BasicServerRef.java:1016)
	at weblogic.work.ExecuteThread.execute(ExecuteThread.java:200)
	at weblogic.work.ExecuteThread.run(ExecuteThread.java:172)

da cosa dipende secondo voi? I file di configurazione dovrebbero essere giusti.
ciao