JavaFX Launch Failure on Ubuntu from JNI

[Kevin Rushforth]

Point #1 is one of the known limitations of using javafx modules on the 
classpath (and is one of the reasons we recommend against it), so that's 
not surprising. And I see you found the workaround.

I wonder if it might have something to do with a shared library that is 
being loaded in one case and not the other, but that's just a vague 
guess. Maybe someone else will spot something.

Since you have something minimal that reproduces the problem for you, 
can you file a bug?

-- Kevin


On 1/19/2022 4:07 PM, Steve Hannah wrote:
> I've reduced the problem down to something minimal and have found that:
>
> 1. If your main class extends Application, and you try to run it like:
> java -jar MyApplication.jar
>
> It will fail immediately with:
> Error: JavaFX runtime components are missing, and are required to run this
> application
>
> 2. If you "trick" it, by making your Application class a separate class
> that you call from your main class, it will run fine using:
> java -jar MyApplication.jar
>
> 3. It will also run fine in this scenario using
> -Djava.class.path=MyApplication.jar instead of -jar:
> java -Djava.class.path=MyApplication.jar Main
>
> 3. If I try to simulate the exact same thing with my own launcher, it will
> hang somewhere in the JavaFX initialization:
>
> with javafx.verbose=true, the output is:
>
> System.loadLibrary(prism_es2) succeeded
> JavaFX: using com.sun.javafx.tk.quantum.QuantumToolkit
> System.loadLibrary(glass) succeeded
>
> But it hangs there, and never displays the screen.
>
> The C code for this launcher is:
>
> char *mainClass;
>
> JavaVM *vm;
> JNIEnv *env;
> JavaVMInitArgs vm_args;
> JavaVMOption options[2];
> mainClass = "Main";
> options[0].optionString = "-Djava.class.path=MyApplication.jar";
> options[1].optionString = "-Djavafx.verbose=true";
> vm_args.version = JNI_VERSION_1_2;
> vm_args.options = options;
> vm_args.nOptions = 2;
> vm_args.ignoreUnrecognized = 0;
>
> jobjectArray args;
> jint res = JNI_CreateJavaVM(&vm, (void **)&env, &vm_args);
> if (res < 0) {
>      printf("Can't create Java VM\n");
>      exit(1);
> }
> jclass cls = (*env)->FindClass(env, mainClass);
> if (cls == 0) {
>
>      printf("Main class %s class not found\n", mainClass);
>      exit(1);
> }
> jmethodID mid =
> (*env)->GetStaticMethodID(env, cls, "main", "([Ljava/lang/String;)V");
> if (mid == 0) {
>      printf("main() method not found\n");
>      exit(1);
> }
> //jstring argString = (*env)->NewStringUTF(env, ""); //empty arg list
> args =
>   (*env)->NewObjectArray(env, 0, (*env)->FindClass(env,
> "java/lang/String"), NULL);
> if (args == 0) {
>      printf("Out of memory\n");
>      exit(1);
> }
>
> (*env)->CallStaticVoidMethod(env, cls, mid, args);
>
>
>
> Can anyone spot any differences between that and running with the "java"
> binary:?
> java -Djava.class.path=MyApplication.jar Main
>
> I have experimented both with JDKs that include JavaFX (e.g. Zulu) and ones
> that do not (e.g. AdoptOpenJDK).  Both exhibit the same behaviour (except
> with AdoptOpenJDK, I also add the javafx jars to the classpath).
>
> For this test I'm using JDK 11 on Mac OS Mojave, but it is consistent with
> my earlier troubles on Ubuntu (also JDK11).
>
>
> Best regards
>
> Steve
>
>
> On Wed, Jan 19, 2022 at 3:06 PM John Neffenger <john at status6.com> wrote:
>
>> On 1/19/22 2:12 PM, Steve Hannah wrote:
>>> I have been resisting using modules for a long time because it just makes
>>> things more complicated, ...
>> It also makes some things easier, though, and certainly smaller. It's
>> easier to use an old-school Makefile with modules, and using 'jlink' can
>> get a simple Hello World JavaFX application and Java runtime down to
>> just 31 megabytes.
>>
>> Here's my minimal, no-magic example:
>>
>> https://github.com/jgneff/hello-javafx
>>
>> with a simple Makefile:
>>
>> https://github.com/jgneff/hello-javafx/blob/main/Makefile
>>
>> and a Maven POM for use online with Maven Central or offline with a
>> local Debian- or Ubuntu-built Maven repository:
>>
>> https://github.com/jgneff/hello-javafx/blob/main/pom.xml
>>
>> John
>>
>