How to close a Jframe from my FXML controller class?

Question

I have a swing application and have to integrate new javafx FXML files into it. I use a JFXPanel to open my FXML form. The exit button is created on the FXML form. My controller class implements the event of that button. But how do I close the Jframe from my swing application?

My JavaFX Controller class (method)

    @FXML
    private void doExit(ActionEvent event) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                Stage stage = (Stage) btnExit.getScene().getWindow();
                stage.close();
            }
        });
    }

Swing application start load my JFXPanel

JFrame frame = new JFrame("");
                frame.setLayout(new BorderLayout());
                final JFXPanel jfxPanel = new JFXPanel();
                frame.add(jfxPanel, BorderLayout.CENTER);
                frame.setDefaultCloseOperation(JFrame.HIDE_ON_CLOSE);
                frame.setVisible(true);
                SwingUtilities.invokeLater(() -> initPrijsMutatieFX(jfxPanel));