launching JavaFX in 11

[Kevin Rushforth]

Hi Johan,

The intention is to launch using --module-path

     java --module-path path-to-sdk/javafx-sdk-11/lib ...

For non-modular applications you also need to add the modules to the 
module graph, for example:

     java --module-path path-to-sdk/javafx-sdk-11/lib --add-modules 
javafx.fxml,javafx.controls ...

You say that running an app from maven works fine. Have you verified 
that the jar files you publish to Maven include a module-info.class file 
in each modular jar?

I suspect that many things could be made to work with javafx modules on 
the classpath instead of the module path, but I don't really recommend 
that. I suspect there will be a few things that won't work without some 
modifications. I think effort would be better spent getting everything 
to work with javafx.* modules as proper named modules.

-- Kevin


On 6/5/2018 6:40 AM, Johan Vos wrote:
> Hi,
>
> I'm a bit confused on the different options for launching JavaFX
> applications with the latest Java 11 code.
> When running an app from maven, it worked fine. Maven uses the classpath
> and not the module path, so I assumed that running the same app using
>
> java -cp all-javafx-jars Main
>
> would work too. But it doesn't. The error I got is this:
>
> Error: JavaFX runtime components are missing, and are required to run this
> application
>
> This error comes from sun.launcher.LauncherHelper in the java.base module.
> The reason for this is that the Main app extends Application and has a main
> method. If that is the case, the LauncherHelper will check for the
> javafx.graphics module to be present as a named module:
>
> Optional<Module> om =
> ModuleLayer.boot().findModule(JAVAFX_GRAPHICS_MODULE_NAME);
>
> If that module is not present, the launch is aborted.
> Hence, having the JavaFX libraries as jars on the classpath is not allowed
> in this case.
>
> Fair, but that doesn't explain why it works via maven. The reason is that
> maven doesn't start a new VM process, hence the main class is in this
> case  org.codehaus.plexus.classworlds.launcher.Launcher which does not
> extend Application, hence it doesn't do the check on javafx.graphics module
> to be present as a named module, and when the required jars (including
> native code) are on the classpath, it works fine.
>
> I thought the check on the main class extending
> javafx.application.Application was removed from the core JDK, but it is
> still there, so I understand why it works using maven and fails using a
> standalone java invocation.
>
> While I fully agree the goal is to have the JavaFX modules as named modules
> on the module path, I think this will create confusion. A simple workaround
> is to have a separate main class that doesn't extend Application, but that
> seems a real dirty solution.
>
> But maybe I'm missing something?
>
> - Johan