[FIXED] Why LauncherImpl.launchApplication() (javaFX launcher) in the main class are launching InvocationTargetException and calling launch() not?

Issue

I´m using javaFX (13.0.2) to make a project and I need to use a preloader, but the LauncherImpl.launchApplication() is not successful.

code:

package classes;

import com.sun.javafx.application.LauncherImpl;
import javafx.application.Application;
import javafx.stage.Stage;

public class Main extends Application {

    @Override
    public void start(Stage primaryStage) {
        System.out.println("start");
    }
    @Override
    public void init() throws Exception {
        System.out.println("init");
    }

    public static void main(String[] args) {
        LauncherImpl.launchApplication(Main.class, UIloadSystem.class, args); // - Not works
        LauncherImpl.launchApplication(Main.class, args); // - Not works
        //launch(Main.class, args); - Works
    }
}

Yes, is a very simple code

Error:

java.lang.reflect.InvocationTargetException
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:567)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:464)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:363)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:567)
    at java.base/sun.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:1051)
Caused by: java.lang.IllegalAccessError: class classes.Main (in unnamed module @0x1936f0f5) cannot access class com.sun.javafx.application.LauncherImpl (in module javafx.graphics) because module javafx.graphics does not export com.sun.javafx.application to unnamed module @0x1936f0f5
    at classes.Main.main(Main.java:30)
    ... 11 more
Exception running application classes.Main

I researched on top of this part class classes.Main (in unnamed module @0x1936f0f5) cannot access class com.sun.javafx.application.LauncherImpl (in module javafx.graphics) because module javafx.graphics does not export com.sun.javafx.application to unnamed module @0x1936f0f5 , but
I didn't find this event anywhere.

If are imporant, I'm using ItelliJ IDEA and the VM options are --module-path ${PATH_TO_FX} --add-modules javafx.controls,javafx.fxml

Sorry for my english, if are some grammatical errors :|

Solution

com.sun.javafx.application.LauncherImpl is private API and not intended for normal developers. Note the fact it starts com.sun. All the public JavaFX API is contained in packages javafx.*. From Java 9 onwards private API is no longer accessible, however some older tutorials still exist.

To use a preloader the following approach should be taken after Java 9.

public static void main(String[] args){
    System.setProperty("javafx.preloader", UIloadSystem.class.getCanonicalName());
    launch(args);
}

Answered By - Adam
Answer Checked By - Gilberto Lyons (JavaFixing Admin)