private void buildRight(ActionEvent event) {

    GridPane grdpn = new GridPane();

    SpinnerValueFactory svf = new SpinnerValueFactory.IntegerSpinnerValueFactory(0, 100);

    Spinner<Integer> numreserved = new Spinner<Integer>();
    numreserved.setValueFactory(svf);
    numreserved.setEditable(true);
    numreserved.setPrefWidth(80);

    Button buttonreserve = new Button("Seleziona numero prenotati");
    grdpn.add(numreserved, 0, 0);
    grdpn.add(buttonreserve, 1, 0);
    buttonreserve.setOnAction(this::buildUserCredentials);

    /*
    GridPane gp = new GridPane();

    Label nameL = new Label("Nome partecipante");
    Label surnameL = new Label("Cognome partecipante");
    Label birthdayL = new Label("Data Nascita");

    TextField txname = new TextField();
    TextField txsurname = new TextField();
    TextField txbirthday = new TextField();

    gp.add(nameL,0,0);
    gp.add(txname,1,0);
    gp.add(surnameL,0,1);
    gp.add(txsurname,1,1);
    gp.add(birthdayL,0,2);
    gp.add(txbirthday,1,2);
    gp.setVgap(10);
    gp.setHgap(3);*/

    sp2.getChildren().add(grdpn);

    gpMediator.send(grdpn, this);
  }