调用EJB出错，请指教？

Question

String url = "t3://144.52.16.2:80";
                String user = null;
                String password = null;
                Properties properties = null;
                try{
                        properties = new Properties();
                        properties.put(Context.INITIAL_CONTEXT_FACTORY, "weblogic.jndi.WLInitialContextFactory");
                        properties.put(Context.PROVIDER_URL, url);
                        if (user != null) {
                                properties.put(Context.SECURITY_PRINCIPAL, user);
                                properties.put(Context.SECURITY_CREDENTIALS, password == null ? "" : password);
                        }
                        Context ctxt = new InitialContext(properties);
                        ctxt.lookup(....