Allan,
if the X server is running while tomcat is running - i.e. your server
has a GUI interface, then tomcat should be able to use it, as DISPLAY
defaults to 127.0.0.1:0 and connections from Xclients on localhost
should be accepted.
If X is on your machine, but you aren't actually running the X Server,
then AWT won't be able to get a context to draw with.
You have several options.
1) Just run X. Start up a minimal GUI on your machine, and leave it.
This can eat resources, however.
2) Use Xvfb, shipped with XFree86 3.3.5?+ and 4.x.x THis is a 'Virtual
framebuffer' that gives you an X Server you can use with AWT without any
actual on-screen display. I have used this for java apps on a headless
SGI machine running IRIX, and it worked well. BE aware that the
bit-depth you set the display to will affect the results of your graphic
drawing operations - i.e. my GIFs have greadient fills, and i notice
major 'banding' if i use a 16bit display as compared to a 32bit display.
3) Use VNC Server. This gives you an X server too, but i think Xvfb
would be preferable.
4) There are AWT libraries floating around that do not require X. I
forget who supplies these.
5) Use another machine's X Server. I wouldn't recommend this for
production use (since graphic operations will require slow network
operations) but it is a nifty demonstration of why X is cool. set
DISPLAY to remotemachine:0 and on the remote machine, type 'xhost
+yourmachine' from a xterm or something. xhost is the command that adds
permission for machines to access the X server.
in cases 2 and 3, you would need to, as part of your tomcat start
script, or just sometime before you start tomcat, to start Xvfb with a
display number of say, 2, and then set an environment variable to point
to it e.g. export DISPLAY=:2
If, for some reason, you are actually having problems connecting to an
already running display, make sure you have a DISPLAY environment
variable set in whatever shell tomcat is running in.
This should get you up and running.
-Pete
> Hi folks,
> I need to use features of the AWT implementation for
> creating off-screen
> images from a servlet.
> Using AWT requires the use of the host machine's
> graphic system which in my
> case is X11 as I am running RH Linux 6.2.
> I would like to know how to grant the servlet
> container access to the X11
> server.
>
> Allan Kamau.
>
>
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