Openjfx ea: error on trying to access private fields

[Kevin Rushforth]

Hi,

The relaxed permissions, which are allowed given the default 
'--illegal-access=permit' mode, only apply to modules that are linked 
into the Java runtime. Modules that are loaded on the module-path are 
subject to strict access controls.

I see three possible solutions for you:

1. Run your application with 'java --add-opens 
javafx.controls/javafx.scene.control=ALL-UNNAMED'
2. jlink the javafx modules into a custom JRE (at which point the javafx 
modules are part of the java runtime)
3. Find a solution that doesn't rely on accessing internal 
implementation details of javafx.controls.

I note that the default for --illegal-access is likely to change to 
"deny" in the not-too-distant future -- possibly as early as JDK 12, so 
it is only a matter of time before this will affect platform classes (at 
which time option #2 stops being available without adding 
'--illegal-access=permit').

Long-term you should explore #3, since accessing internal fields or 
methods is fragile and might stop working at any point.

-- Kevin


On 7/24/2018 4:44 AM, fastegal at swingempire.de wrote:
>
> below is a small app that comes up with a button: on click it wants
> to access a private field (obviouly via reflection) in the button class.
> Due to relaxed permission constraints, that works in all java versions 
> 9/10
> without additional configuration and also with openjdk for non-fx 
> classes.
>
> With the combination of openjdk10 + openjfx-ea (both downloaded from 
> their
> respective download pages at java.net) it throws an error at runtime 
> on clicking:
>
> Exception in thread "JavaFX Application Thread"
> java.lang.reflect.InaccessibleObjectException:
> Unable to make field private javafx.beans.property.BooleanProperty
> javafx.scene.control.Button.defaultButton accessible:
> module javafx.controls does not "opens javafx.scene.control" to 
> unnamed module @b65246
>
> Happens both from the command line (thanks Johan for the concise example,
> easy to understand even for a command line hater like myself :) as 
> from inside eclipse
>
> Any idea what's wrong?
>
>
> public class MinimalAccessFieldFX10Open extends Application {
>
>     private Parent getContent() {
>         Button button = new Button("something to click on");
>
>         button.setOnAction(e -> {
>             // okay
>             Object def = invokeGetFieldValue(Button.class, button, 
> "defaultButton");
>             LOG.info("getting the private field: " + def);
>         });
>         BorderPane pane = new BorderPane(button);
>         return pane;
>     }
>
>     @Override
>     public void start(Stage primaryStage) throws Exception {
>         primaryStage.setScene(new Scene(getContent(), 600, 400));
>         primaryStage.show();
>     }
>
>     public static Object invokeGetFieldValue(Class<?> declaringClass,
>             Object target, String name) {
>         try {
>             Field field = declaringClass.getDeclaredField(name);
>             field.setAccessible(true);
>             return field.get(target);
>         } catch (NoSuchFieldException | SecurityException
>                 | IllegalArgumentException | IllegalAccessException e) {
>             e.printStackTrace();
>         }
>         return null;
>     }
>
>     public static void main(String[] args) {
>         launch(args);
>     }
>
>     @SuppressWarnings("unused")
>     private static final Logger LOG = Logger
> .getLogger(MinimalAccessFieldFX10Open.class.getName());
> }
>