Add System.exit

[koppor]

My JabRef had the grizzly threads running on exit. I don't have the time to debug now.

Maybe, in future, there will be other things taking time to properly shut down.

Therfore, I propose to "just" end the JVM so that nothing is left behind by JabRef.

Mandatory checks

• I own the copyright of the code submitted and I license it under the MIT license
• [/] Change in CHANGELOG.md described in a way that is understandable for the average user (if change is visible to the user)
• [/] Tests created for changes (if applicable)
• [/] Manually tested changed features in running JabRef (always required)
• [/] Screenshots added in PR description (if change is visible to the user)
• [/] Checked developer's documentation: Is the information available and up to date? If not, I outlined it in this pull request.
• [/] Checked documentation: Is the information available and up to date? If not, I created an issue at https://github.com/JabRef/user-documentation/issues or, even better, I submitted a pull request to the documentation repository.

[trag-bot]

Using System.exit() is a harsh way to terminate an application and can prevent proper cleanup. JavaFX's Platform.exit() should handle the shutdown gracefully.

[trag-bot]

Comment merely restates what the code does without providing additional context or reasoning for this drastic measure, violating the principle of meaningful comments.

[Siedlerchr]

I don't get the problem. We already have shutdown cleanup and stopping of threads. Have you checked with Visual VM what's going on?
and you are sure it's not gradle?

[koppor]

I don't get the problem. We already have shutdown cleanup and stopping of threads.
Have you checked with Visual VM what's going on? and you are sure it's not gradle?

Yes, therefore, I wrote following - see the yellow-marked text --> first sentence in the PR description.

[koppor]

On current main (with some tests in CAYW), grizzly is shut down, but something else is not:

Remember: One can start Visual VM by ./gg.cmd gh/oracle/visualvm - gg.cmd is available at https://github.com/eirikb/gg)

[koppor]

We log to JavaFX - maybe, this is causing troubles:

2025-07-15 21:03:58 [] org.glassfish.grizzly.http.server.NetworkListener.shutdownNow()
INFO: Stopped listener bound to [127.0.0.1:23119]
2025-07-15 21:04:28 [] org.jabref.gui.util.UiThreadList.sourceChanged()
ERROR: Error while running on JavaFX thread: java.lang.InterruptedException
        at java.base/java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireSharedInterruptibly(AbstractQueuedSynchronizer.java:1139)
        at java.base/java.util.concurrent.CountDownLatch.await(CountDownLatch.java:230)
        at org.jabref/org.jabref.gui.util.UiThreadList.sourceChanged(UiThreadList.java:32)
        at javafx.base@24.0.1/javafx.collections.transformation.TransformationList.lambda$getListener$0(TransformationList.java:105)
        at javafx.base@24.0.1/javafx.collections.WeakListChangeListener.onChanged(WeakListChangeListener.java:88)
        at javafx.base@24.0.1/com.sun.javafx.collections.ListListenerHelper$SingleChange.fireValueChangedEvent(ListListenerHelper.java:162)
        at javafx.base@24.0.1/com.sun.javafx.collections.ListListenerHelper.fireValueChangedEvent(ListListenerHelper.java:71)
        at javafx.base@24.0.1/javafx.collections.ObservableListBase.fireChange(ObservableListBase.java:246)
        at javafx.base@24.0.1/javafx.collections.FXCollections$UnmodifiableObservableListImpl.lambda$new$0(FXCollections.java:947)
        at javafx.base@24.0.1/javafx.collections.WeakListChangeListener.onChanged(WeakListChangeListener.java:88)
        at javafx.base@24.0.1/com.sun.javafx.collections.ListListenerHelper$SingleChange.fireValueChangedEvent(ListListenerHelper.java:162)
        at javafx.base@24.0.1/com.sun.javafx.collections.ListListenerHelper.fireValueChangedEvent(ListListenerHelper.java:71)
        at javafx.base@24.0.1/javafx.collections.ObservableListBase.fireChange(ObservableListBase.java:246)
        at javafx.base@24.0.1/javafx.collections.ListChangeBuilder.commit(ListChangeBuilder.java:482)
        at javafx.base@24.0.1/javafx.collections.ListChangeBuilder.endChange(ListChangeBuilder.java:541)
        at javafx.base@24.0.1/javafx.collections.ObservableListBase.endChange(ObservableListBase.java:210)
        at javafx.base@24.0.1/javafx.collections.ModifiableObservableListBase.add(ModifiableObservableListBase.java:200)
        at java.base/java.util.AbstractList.add(AbstractList.java:113)
        at org.jabref/org.jabref.gui.logging.LogMessages.add(LogMessages.java:30)
        at org.jabref/org.jabref.gui.logging.GuiWriter.write(GuiWriter.java:28)
        at org.tinylog.impl@2.7.0/org.tinylog.core.TinylogLoggingProvider.output(TinylogLoggingProvider.java:259)
        at org.tinylog.impl@2.7.0/org.tinylog.core.TinylogLoggingProvider.log(TinylogLoggingProvider.java:186)
        at org.tinylog.api.slf4j@2.7.0/org.tinylog.slf4j.AbstractTinylogLogger.log(AbstractTinylogLogger.java:501)
        at jul.to.slf4j@2.0.17/org.slf4j.bridge.SLF4JBridgeHandler.callLocationAwareLogger(SLF4JBridgeHandler.java:232)
        at jul.to.slf4j@2.0.17/org.slf4j.bridge.SLF4JBridgeHandler.publish(SLF4JBridgeHandler.java:313)
        at java.logging/java.util.logging.Logger.log(Logger.java:962)
        at java.logging/java.util.logging.Logger.doLog(Logger.java:989)
        at java.logging/java.util.logging.Logger.log(Logger.java:1055)
        at org.glassfish.grizzly.http.server@4.0.2/org.glassfish.grizzly.http.server.NetworkListener.shutdownNow(NetworkListener.java:859)
        at org.glassfish.grizzly.http.server@4.0.2/org.glassfish.grizzly.http.server.HttpServer.removeListener(HttpServer.java:188)
        at org.glassfish.grizzly.http.server@4.0.2/org.glassfish.grizzly.http.server.HttpServer.shutdownNow(HttpServer.java:382)
        at org.jabref.jabsrv/org.jabref.http.manager.HttpServerThread.interrupt(HttpServerThread.java:50)
        at org.jabref.jabsrv/org.jabref.http.manager.HttpServerManager.stop(HttpServerManager.java:41)
        at org.jabref/org.jabref.gui.JabRefGUI.lambda$stop$4(JabRefGUI.java:458)
        at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:545)
        at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:328)
        at java.base/java.lang.VirtualThread.run(VirtualThread.java:466)
2025-07-15 21:04:58 [JavaFX Application Thread] org.jabref.logic.util.HeadlessExecutorService.gracefullyShutdown()
ERROR: HeadlessExecutorService did not terminate