Hello, Kevin
Yes, I filed that enhancement request.
When user presses CTRL+C then SIGINT signal is sent to the process. SIGINT is a
signal used to request a graceful termination of a process, typically initiated
by the user(more details are here https://stackoverflow.com/a/4047975).
Now, we are talking about GUI application (if we didn't develop a GUI
application, we wouldn't need JavaFX, would we?). So, our GUI application gets
SIGINT or SIGTERM (I didn't test with SIGTERM, but I think result is the same)
and after that immediately stops working because of the damned shutdown hook.
For example, if our application is a simple text editor, our application can't
let user save file. Why? Because GUI platform doesn't work anymore.
That's why I opened that issue. I saw you suggested working with exceptions.
But that issue is not about exceptions, but about letting application
developers control when to shutdown platform.
Best regards, Pavel
On 7/26/24 16:54, Kevin Rushforth wrote:
I am not sure we will want to disabling the shutdown hook, since that is likely
to cause problems (they were added to fix bugs that resulted from applications
calling System.exit()).
In the bug report for JDK-8320923, you mentioned that Swing doesn't have this
problem, but that's because Swing closes all of its windows before effecting
the shutdown (that's something JavaFX could do as well).
Related to this, I see that someone (perhaps it was you?) just filed an
enhancement request to consider optionally disabling the shutdown hook:
https://bugs.openjdk.org/browse/JDK-8337247
I haven't looked at it closely, but my sense is that disabling the shutdown
hooks in a way that tries to keep the JavaFX runtime active is unlikely to be
something we want to do. I added the following comment to the above JBS issue
with some initial thoughts:
--------------------------------------------------
“I can take a look, but I do not think we will implement this Enhancement
request -- at least not as described.
Instead, we might consider whether this can be done using existing mechanisms,
such as overriding Application::exit. If it turns out there isn't a suitable
existing mechanism, we might consider other solutions. A couple possibilities:
1. Provide a Platform setting that will cause Platform.runLater to throw an
exception if called after shutdown (this might be require adding a few
try/catch blocks in our own cleanup code)
2. Rather than a setting as described above, create a new overload of
Platform.runLater that throws an exception if the Platform is not able to queue
the request.
There might be other solutions.”
-------------------------------------------------------
-- Kevin
On 7/25/2024 8:43 AM, PavelTurk wrote:
Hello all.
JavaFX adds its own shutdown hook. That gives many problems when it is
necessary to work with application,
when system is shutting down, for example, if user presses CTRL+C. The first
problem I described here -
https://bugs.openjdk.org/browse/
Another problem is that after pressing CTRL+C JavaFX seems not to respond
anymore. For example I've
observed that if after that we try to do Platform.runLater(() -> myCode is
here), then myCode will never execute.
So, it is necessary to check in system, how it is shutting down, if it is. And
this problem creates other problems.
Before opening a feature request, I decided to ask JavaFX developers, if it
possible to disable JavaFX shutdown hook.
I mean, if there is no system property (something like
javafx.shutdownhook.disabled), it will be added, but if I want
to call Platform.exit() manually I want to be able to disable JavaFX shutdown
hook.
Best regards, Pavel
