loginButton.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent event) {
                String username = usernameTextBox.getText();
                String password = passwordField.getText();
                String[] credentials = { username, password };
                String query = "SELECT \"Type\" FROM \"Users\" where LOWER(\"Username\") = LOWER(?) AND \"Password\" = ?";
                final ClientQuery userTypeQuery = new ClientQuery(query, credentials);

                ExecutorService executor = Executors.newCachedThreadPool();
                Future<ClientQuery> future = executor.submit(new Callable<ClientQuery>(){

                    @Override
                    public ClientQuery call() throws Exception {
                        return QuerySender.sendQuery(userTypeQuery, socket);
                    }
                });

                ClientQuery userTypeResponse = null;
                try {
                    userTypeResponse = future.get();
                } catch (InterruptedException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                } catch (ExecutionException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }


                // getting type of username based on the response from server
                // 0 - superadmin, 1 - normal admin, 2 - buyer
                UserType type;
                try {
                    type = UserType.values()[Integer.parseInt(userTypeResponse.getResponse().get(0)[0])];
                } catch (Exception exception) {
                    type = null;
                }
                if (type == null) {
                    invalidPassLabel.setVisible(true);
                } else {
                    switch (type) {
                    case SuperAdmin:
                        new SuperAdmin(username);
                        primaryStage.close();
                        break;

                    case NormalAdmin:
                        new NormalAdmin(username);
                        primaryStage.close();
                        break;

                    case Buyer:
                        new Buyer(username);
                        primaryStage.close();
                        break;
                    }
                }
            }
        });