Exactly !
In fact, I'm in mastery of ... nothing ! But I tried to workaround this problem
and found that Java Process class lacks something ! I was working in Eclipse
and you can process while testing (the red button in console view) but shutdown
hooks are not called. So I dug a little to understand why Eclipse team said
that it is not possible (up to now). Indeed, Eclipse spawns a new Process
Object (a new JVM in fact) but can't close it gracefully. I think other
application / programs may need such functionnality so I post on this list to
have advices of specialists of openJdk.
You are right again on the second part ! Actually I did exactly that in my
applications, only for debug/test, very simple :
boolean loopz = true;
InputStreamReader isr = null;
BufferedReader br = null;
try {
isr = new InputStreamReader(System.in);
br = new BufferedReader(isr);
while (loopz) {
String userInput = br.readLine();
System.out.println("input => "+userInput);
if (userInput.equalsIgnoreCase("quit") ||
userInput.equalsIgnoreCase("exit")) {
System.exit(0);
}
}
}
catch (Exception er) {
er.printStackTrace();
loopz = false;
}
finally {
try { br.close(); } catch (Exception e) {}
try { isr.close(); } catch (Exception e) {}
}
However I think it could be a good add to Java to make a Process having better
control on its own child termination.
Thanks !
Nicolas Le Picard
-----Message d'origine-----
De : Peter Levart [mailto:peter.lev...@gmail.com]
Envoyé : mardi 4 mars 2014 15:47
À : LE PICARD NICOLAS; Alan Bateman; Krystal Mok
Cc : core-libs-dev@openjdk.java.net
Objet : Re: How to close a Process and having shutdown hooks called ?
On 03/04/2014 02:09 PM, LE PICARD NICOLAS wrote:
> I didn't know for jdk8 functions destroy and the new one destroyForcibly...
>
> And Jonathan was right in his previous answer, I was looking for a solution
> in Java, I mean a portable one like in Process class, like the
> "destroyGracefully".
> I am looking to signals because it seems to be a simple way to achieve this
> "portable" solution, maybe I'm wrong.
>
> It would be useful (as you said) to have a function to kill "gracefully"
> through Process class, no ?
>
> Nicolas Le Picard
Hi Nicolas,
So you're spawning a Java sub-process from a Java master process using
java.lang.Process, do I understand correctly?
Are you in control of the code that represents the child sub-process? Is this
code already using System.in (STDIN) stream for anything? If the answers are
YES and NO respectively, then you may be able to use the System.in in the
sub-process (spawn a special monitoring thread) and
Process.getOutputStream() in the master process to establish a one way channel
for passing commands in direction: master process -> sub-process. One of those
commands could be "shutdown" for example, that would trigger a System.exit() in
the sub-process. This way you could make the shut-down hooks in sub-process be
executed before exiting...
Regards, Peter
>
> -----Message d'origine-----
> De : Alan Bateman [mailto:alan.bate...@oracle.com] Envoyé : mardi 4
> mars 2014 13:12 À : Krystal Mok Cc : LE PICARD NICOLAS;
> core-libs-dev@openjdk.java.net Objet : Re: How to close a Process and
> having shutdown hooks called ?
>
> On 04/03/2014 11:51, Krystal Mok wrote:
>> Hi Nicolas,
>>
>> Looks like a well discussed question. On Posix systems, SIGTERM
>> should work for you. That's the default signal sent by the 'kill' command on
>> Linux.
>> e.g. please take a look here:
>> http://stackoverflow.com/questions/2541597/how-to-gracefully-handle-t
>> h
>> e-sigkill-signal-in-java
>>
>> - Kris
>>
> I think he's on Windows and is looking for destroy to use something other
> than TerminateProcess.
>
> As background, the destroy method was confusingly specified to kill the
> sub-process forcibly but it wasn't implemented this way everywhere. On
> Unix/Linux then the long standing implementation used SIGTERM and so no
> guarantee that it would cause the sub-process to terminate. This mismatch was
> examined in JDK 8 (you'll need to go through the archives of this mailing
> list to see the discussion) and the javadoc updated to make it clear that it
> is implementation specific as to whether it is done forcibly or not. In
> addition a new destroyForcibly was added to do the SIGKILL or
> TerminateProcess for cases where you really want to kill the child. There
> isn't a corresponding destroyGracefully but clearly this would be useful if
> were feasible to implement everywhere.
>
> -Alan.
