Openjfx ea: error on trying to access private fields
Kevin Rushforth
kevin.rushforth at oracle.com
Tue Jul 24 12:18:47 UTC 2018
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());
> }
>
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