Java 9 JavaFX Preloader

In Java 8 I can launch a JavaFX application with a preloader using the following method:

LauncherImpl.launchApplication(WindowMain.class, WindowMainPreloader.class, 
new String[]{...});

I prefer to start it from code, like above, instead of using a deploy configuration, because I don't want the graphical interface to start every time I start the application, but only after some code that has computed that the application should run in GUI mode.

I was using the class "com.sun.javafx.application.LauncherImpl", but apparently in Java 9 all classes starting with "com.sun" are removed. So, how can I start the application with the preloader in Java 9?

There is a comment on the answer to this question:

How to create splash screen as a Preloader in JavaFX standalone application?

system property javafx.preloader=classname seems to work too.

I didn't try it, but perhaps you could try setting that property and just launching your main app via the public Application.launch(appClass, args) API and perhaps the preloader will launch first.

Looking into the code for Application.launch, it seems that this would work. Here is the code which is eventually invoked, copied from the Java 8 source:

public static void launchApplication(final Class<? extends Application> appClass,
        final String[] args) {

    Class<? extends Preloader> preloaderClass = savedPreloaderClass;

    if (preloaderClass == null) {
        String preloaderByProperty = AccessController.doPrivileged((PrivilegedAction<String>) () ->
                System.getProperty("javafx.preloader"));
        if (preloaderByProperty != null) {
            try {
                preloaderClass = (Class<? extends Preloader>) Class.forName(preloaderByProperty,
                        false, appClass.getClassLoader());
            } catch (Exception e) {
                System.err.printf("Could not load preloader class '" + preloaderByProperty +
                        "', continuing without preloader.");
                e.printStackTrace();
            }
        }
    }

    launchApplication(appClass, preloaderClass, args);
}

So you should be able to launch an app with a preloader using:

System.setProperty("javafx.preloader", "my fully qualified preloader class name");
Application.launch(myMainClass, args);