JavaFX Webview: addEventListener on form submit. How to get the button that submitted?

I know how to put an event listener on a form submit. However, I'd like to know which button, if any, triggered the form submit. Is there a way to get that information from the resulting event?

Something like a submitter property, to return the element that submitted the form.

webEngine.getLoadWorker().stateProperty().addListener(new ChangeListener<State>() {
    private void changed(ObservableValue<? extends Worker.State> observable,Worker.State oldState,Worker.State newState) {
        if (newState == Worker.State.SUCCEEDED) {
            // Set the "submit" handler to get the data on submission.
            nodeList = doc.getElementsByTagName("form");
            for (int i = 0; i < nodeList.getLength(); i++) {
                EventTarget target = (EventTarget) nodeList.item(i);
                target.addEventListener("submit", listenerSubmit, false);
            }
        }
    }

    private void getDataAndSubmit(org.w3c.dom.events.Event event) {
        Element button = event.getSubmitter(); // DOESN'T WORK
        ....
    }
});