Re: [Wrapper-user] Starting Swing application from Linux daemon

[Leif M. <le...@ta...>]

Lars,
I am very sorry for the delay on this.  I discussed this with the team
a couple weeks ago and was under the impression it had been replied
to.

The problem here is that Java decides where to display its GUI by
looking at the DISPLAY environment variable.

That DISPLAY environment variable does not and can not exist when a
daemon process is launched on startup.   It will be set in any
environments that are created from within the X Windows environment,
or which are set manually after the Window manager has been started.

If the Wrapper launches the JVM before the Window manager is launched
and a user has logged in, then the JVM will already exist with an
environment that does not have a DISPLAY variable.

It might be possible to get this working if the Wrapper sets the
DISPLAY variable and you force a restart of the JVM whenever a user
logs in.  I will have to test that a bit more.  Is this something that
would make sense for your application?

One solution that I have seen implemented in the past is to have one
JVM which is running as a Daemon work horse.  Then you launch a second
JVM whenever the user logs in that is in charge of the user interface
within the window environment.  You could then use any number of
technologies to communicate between the two JVMs.   The GUI JVM would
terminate when the user logged out

We were talking about coming up with a recommended methodology for
setting up systems like this.   Starting with Windows Vista, it is no
longer possible to have true interactive services, so we need to
provide another solution to Windows users as well.

I am interested in your feedback on what will and won't work for you,
as well as what exactly you are hoping to be able to do and why.

Once again sorry for the long delay.

Cheers,
Leif


On Thu, Nov 26, 2009 at 5:05 PM, Lars Schnoor <Lar...@if...> wrote:
> Hi again
> I guess since there haven't been any replies to this problem, that there
> is no solution?
>
> Lars
>
> Lars Schnoor wrote:
>> Hi
>> I would like to have my application which is started as a Linux daemon
>> to present a graphical user interface to the user. The user interface is
>> written in Java Swing.
>> When I try to start the user interface I get an
>> java.awt.HeadlessException:
>> No X11 DISPLAY variable was set, but this program performed an operation
>> which requires it.
>> Is there a solution to this?
>> Thanks in advance!
>>
>> Lars