Nsryjdtyk

Note: I have very little experience with the Module system introduced in Java 9.

I have a Java Process which should run another Jar file by loading and executing it through reflection.
Note that both Jar files depend on the JavaFX framework which got detached from the JDK in Version 11 and as a result could get loaded a second time.

Here the Original version which worked on JDK version 8:

val ideFile = File(binFolder, "Sk-IDE.jar")

val classLoader = ClassLoader.getSystemClassLoader() as URLClassLoader

val method = URLClassLoader::class.java.getDeclaredMethod("addURL", URL::class.java)

method.isAccessible = true

method.invoke(classLoader, ideFile.toURI().toURL())

val coreManager = Class.forName("com.skide.CoreManager")

val instance = coreManager.newInstance()

coreManager.getDeclaredMethod("bootstrap", Array<String>::class.java).invoke(instance, State.args)

(The Reflective call to addURL was necessary because otherwise the loader Jar was unable to load its fxml files)

This approach throws this Exception on JDK 11:

java.lang.ClassCastException: class jdk.internal.loader.ClassLoaders$AppClassLoader cannot be cast to class java.net.URLClassLoader (jdk.internal.loader.ClassLoaders$AppClassLoader and java.net.URLClassLoader are in module java.base of loader 'bootstrap')

The approach to create a new URLClassLoader:

val child = URLClassLoader(arrayOf(URL(ideFile.toURI().toURL().toString())), Installer::class.java.classLoader)

val coreManager = Class.forName("com.skide.CoreManager", true, child)

val instance = coreManager.newInstance()

Platform.runLater {

    coreManager.getDeclaredMethod("bootstrap", Array<String>::class.java).invoke(instance, State.args)

}

Throws a JavaFX related Exception:

Exception in thread "JavaFX Application Thread" [20.11.2018 20:13:41 | ERROR] java.security.PrivilegedActionException: java.lang.reflect.InvocationTargetException

[20.11.2018 20:13:41 | ERROR]   at java.base/java.security.AccessController.doPrivileged(Native Method)

[20.11.2018 20:13:41 | ERROR]   at com.sun.javafx.application.PlatformImpl.lambda$runLater$11(PlatformImpl.java:427)

[20.11.2018 20:13:41 | ERROR]   at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:96)

[20.11.2018 20:13:41 | ERROR]   at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)

[20.11.2018 20:13:41 | ERROR]   at com.sun.glass.ui.win.WinApplication.lambda$runLoop$3(WinApplication.java:174)

[20.11.2018 20:13:41 | ERROR]   at java.base/java.lang.Thread.run(Thread.java:834)

[20.11.2018 20:13:41 | ERROR] Caused by: java.lang.reflect.InvocationTargetException

[20.11.2018 20:13:41 | ERROR]   at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

[20.11.2018 20:13:41 | ERROR]   at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)

[20.11.2018 20:13:41 | ERROR]   at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

[20.11.2018 20:13:41 | ERROR]   at java.base/java.lang.reflect.Method.invoke(Method.java:566)

[20.11.2018 20:13:41 | ERROR]   at com.skide.installer.Installer$start$2$1$1.run(Installer.kt:249)

[20.11.2018 20:13:41 | ERROR]   at com.sun.javafx.application.PlatformImpl.lambda$runLater$10(PlatformImpl.java:428)

[20.11.2018 20:13:41 | ERROR]   ... 6 more

[20.11.2018 20:13:41 | ERROR] Caused by: javafx.fxml.LoadException: 

unknown path:9



[20.11.2018 20:13:41 | ERROR]   at javafx.fxml.FXMLLoader.constructLoadException(FXMLLoader.java:2625)

[20.11.2018 20:13:41 | ERROR]   at javafx.fxml.FXMLLoader.access$700(FXMLLoader.java:105)

[20.11.2018 20:13:41 | ERROR]   at javafx.fxml.FXMLLoader$ValueElement.processAttribute(FXMLLoader.java:930)

[20.11.2018 20:13:41 | ERROR]   at javafx.fxml.FXMLLoader$InstanceDeclarationElement.processAttribute(FXMLLoader.java:980)

[20.11.2018 20:13:41 | ERROR]   at javafx.fxml.FXMLLoader$Element.processStartElement(FXMLLoader.java:227)

[20.11.2018 20:13:41 | ERROR]   at javafx.fxml.FXMLLoader$ValueElement.processStartElement(FXMLLoader.java:752)

[20.11.2018 20:13:41 | ERROR]   at javafx.fxml.FXMLLoader.processStartElement(FXMLLoader.java:2722)

[20.11.2018 20:13:41 | ERROR]   at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2552)

[20.11.2018 20:13:41 | ERROR]   at javafx.fxml.FXMLLoader.load(FXMLLoader.java:2450)

[20.11.2018 20:13:41 | ERROR]   at com.skide.CoreManager$bootstrap$1.invoke(CoreManager.kt:47)

[20.11.2018 20:13:41 | ERROR]   at com.skide.CoreManager$bootstrap$1.invoke(CoreManager.kt:24)

[20.11.2018 20:13:41 | ERROR]   at com.skide.CoreManager.bootstrap(CoreManager.kt:136)

[20.11.2018 20:13:41 | ERROR]   ... 12 more

[20.11.2018 20:13:41 | ERROR] Caused by: java.lang.ClassNotFoundException: com.skide.gui.controllers.SplashGuiController

[20.11.2018 20:13:41 | ERROR]   at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:583)

[20.11.2018 20:13:41 | ERROR]   at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:178)

[20.11.2018 20:13:41 | ERROR]   at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:521)

[20.11.2018 20:13:41 | ERROR]   at javafx.fxml.FXMLLoader$ValueElement.processAttribute(FXMLLoader.java:928)

[20.11.2018 20:13:41 | ERROR]   ... 21 more

Whats the best way to solve this?

Regards,
Liz3

EDIT

With the help of xtratic, the solution was actually straight forward:

I simply added the child URLClassloader to the CoreManager#bootstrap reflective call, the bootstrap method of the CoreManager(loaded jar) than passes that URLClassloader to all FXML loaders.

When you are using the new URLClassLoader it seems like the method is being invoked but is throwing a javafx.fxml.LoadException which gets wrapped by the PrivilegedActionException and InvocationTargetException.

Even though you load your class with your own URLClassloader it looks like the FXML parser is trying to load the FX beans with the built-in classloader, which doesn't know about those classes in the FXML.

You'll need to make FXMLLoader use the right classloader that contains all the classes referenced by the fxml. Read the source of FXMLLoader to get an idea of how it handles classloading. You may need to modify the library doing the fxml loading if possible. Look into FXMLLoader.setClassLoader(urlClassLoader) or possibly setting a SecurityManager so that the FXMLLoader will use the calling classloader.

FXMLLoader.java

/**

 * Returns the classloader used by this serializer.

 * @since JavaFX 2.1

 */

@CallerSensitive

public ClassLoader getClassLoader() {

    if (classLoader == null) {

        final SecurityManager sm = System.getSecurityManager();

        final Class caller = (sm != null) ?

                Reflection.getCallerClass() :

                null;

        return getDefaultClassLoader(caller);

    }

    return classLoader;

}



private static ClassLoader getDefaultClassLoader(Class caller) {

    if (defaultClassLoader == null) {

        final SecurityManager sm = System.getSecurityManager();

        if (sm != null) {

            final ClassLoader callerClassLoader = (caller != null) ?

                    caller.getClassLoader() :

                    null;

            if (needsClassLoaderPermissionCheck(callerClassLoader, FXMLLoader.class.getClassLoader())) {

                sm.checkPermission(GET_CLASSLOADER_PERMISSION);

            }

        }

        return Thread.currentThread().getContextClassLoader();

    }

    return defaultClassLoader;

}

I had a guess that Java11 may have changed it's classloader.

See this link (contents pasted below)

Casting To URL Class Loader

Java 9 and the module system improved the platform’s class loading strategy, which is implemented in a new type and in Java 11 the application class loader is of that type. That means it is not a URLClassLoader, anymore, so the occasional (URLClassLoader) getClass().getClassLoader() or (URLClassLoader) ClassLoader.getSystemClassLoader() sequences will no longer execute. This is another typical example where Java 11 is backwards compatible in the strict sense (because that it’s a URLCassLoader was never specified) but which can nonetheless cause migration challenges.

Symptoms

This one is very obvious. You’ll get a ClassCastException complaining that the new AppClassLoader is no URLClassLoader:

Exception in thread "main" java.lang.ClassCastException:

java.base/jdk.internal.loader.ClassLoaders$AppClassLoader

cannot be cast to java.base/java.net.URLClassLoader

    at monitor.Main.logClassPathContent(Main.java:46)

    at monitor.Main.main(Main.java:28)

Fixes

The class loader was probably cast to access methods specific to URLClassLoader. If so, you might have to face some serious changes.

...

If you’ve used the URLClassLoader to dynamically load user provided code (for example as part of a plugin infrastructure) by appending to the class path, then you have to find a new way to do that as it can not be done with Java 11. You should instead consider creating a new class loader for that. This has the added advantage that you’ll be able to get rid of the new classes as they are not loaded into the application class loader. You should also read up on layers – they give you a clean abstraction for loading an entirely new module graph.