Problem using JavaFX Application class

[Sander Mak]

Hi David,

Thanks for the quick response. Here is a small sample project: https://bitbucket.org/sandermak/javafx-application/src, the compilerun.sh can be used to start the app. I already alluded to the solution you propose in the original post. Indeed, when exporting the class that extends Application (qualified to javafx.graphics or not, both will do) it works.

However, is such an application class really something I want to export to other modules? Of course using a qualified export the scope can be restricted to the javafx.graphics module, and that's what I ended up doing. In general, I think it's interesting  that many frameworks want reflective access to what are essentially internal implementation classes. Spring comes to mind, you'd want to export interfaces but not Spring bean implementation classes, even though the framework needs access to instantiate them. As has been discussed before on this list, ServiceLoader has a special super-power in this regard, and I sort of expected JavaFX Application handling to have that same superpower for instantiating the Application class.

One more follow-up question: when I remove the main() method that invokes launch (see here: https://bitbucket.org/sandermak/javafx-application/diff/src/applicationmodule/application/Main.java?diff2=fca74ffbc28d&at=without-main), the following error comes up (build 9-ea+106-jigsaw-nightly-h4498-20160221):

Error: Main method not found in class application.Main, please define the main method as:
   public static void main(String[] args)
or a JavaFX application class must extend javafx.application.Application

On JDK8 the same code runs fine. What's going on there?


Thanks,
Sander

On 23 Feb 2016, at 22:46, David Hill <David.Hill at Oracle.com<mailto:David.Hill at Oracle.com>> wrote:

On 2/23/16, 3:37 PM, Sander Mak wrote:
Hi,

Sander,
   we may not have tested Jigsaw with the path you are trying to take here.

Certainly the common path of a class extending Application will launch properly, and I have been trudging through our test cases working on some odder paths. What I have not been doing in these paths is dealing with a new module, though I would think that would behave similarly to the unnamed module.

It could be that your added complexity here has not been properly dealt with in our FX code.

Do you have a "simple" test case that shows this error?

Looking at the exception I see a lot of stuff going on, and it is hard to see the root right away.

With modules, we have to add read edge code in certain spots when our code has to reach out of the module to a module it does not already know about.

This is the hint here:

(in module javafx.graphics) cannot access class javamodularity.easytext.gui.Main (in module javamodularity.easytext.gui)

Our FX module javafx.graphics cannot see into your module.

The question becomes one of where, and order of operations.

Dave



When trying to run a module with a main class that extends javafx.application.Application, the following exception is thrown by the VM:

Exception in thread "main" java.lang.RuntimeException: Unable to construct Application instance: class javamodularity.easytext.gui.Main
at com.sun.javafx.application.LauncherImpl.launchApplication1(javafx.graphics at 9-ea/LauncherImpl.java:926)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication$140(javafx.graphics at 9-ea/LauncherImpl.java:220)
at java.lang.Thread.run(java.base at 9-ea/Thread.java:804)
Caused by: java.lang.IllegalAccessException: class com.sun.javafx.application.LauncherImpl (in module javafx.graphics) cannot access class javamodularity.easytext.gui.Main (in module javamodularity.easytext.gui) because module javamodularity.easytext.gui does not export javamodularity.easytext.gui to module javafx.graphics
at sun.reflect.Reflection.throwIllegalAccessException(java.base at 9-ea/Reflection.java:465)
at sun.reflect.Reflection.throwIllegalAccessException(java.base at 9-ea/Reflection.java:456)
at sun.reflect.Reflection.ensureMemberAccess(java.base at 9-ea/Reflection.java:98)
at java.lang.reflect.AccessibleObject.slowCheckMemberAccess(java.base at 9-ea/AccessibleObject.java:370)
at java.lang.reflect.AccessibleObject.checkAccess(java.base at 9-ea/AccessibleObject.java:362)
at java.lang.reflect.Constructor.newInstance(java.base at 9-ea/Constructor.java:435)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$146(javafx.graphics at 9-ea/LauncherImpl.java:838)
at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$160(javafx.graphics at 9-ea/PlatformImpl.java:351)
at com.sun.javafx.application.PlatformImpl.lambda$null$158(javafx.graphics at 9-ea/PlatformImpl.java:320)
at java.security.AccessController.doPrivileged(java.base at 9-ea/Native Method)
at com.sun.javafx.application.PlatformImpl.lambda$runLater$159(javafx.graphics at 9-ea/PlatformImpl.java:319)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(javafx.graphics at 9-ea/InvokeLaterDispatcher.java:96)

This can be solved by adding a (qualified) export in the module-info of the module I'm trying to run (inspired by the helpful error message, nice!):

exports javamodularity.easytext.gui to javafx.graphics;

However, that's not really a satisfactory solution. Looks like LauncherImpl also needs to setup a readability relation on-the-fly, with the caveat that the class extending Application must always be exported by the application developer for this to work. Is this the solution we can expect, or are there any other plans for this situation?


Regards,
Sander


--
David Hill<David.Hill at Oracle.com<mailto:David.Hill at Oracle.com>>
Java Embedded Development

"A man's feet should be planted in his country, but his eyes should survey the world."
-- George Santayana (1863 - 1952)