X11 error with Java Screenshot agent running as a service
 

I have created a small Java Agent that run on boot as a service on a CentOS box (linux). I am trying to implement in to the agent a screen capture function, where a screenshot is taken every 10 seconds and sent to a directory.

I have managed to do this, and it runs fine when I run it when logged in as a user.
However when I start the log agent as a service, I get the following error:

No X11 DISPLAY variable was set, but this program performed an operation which requires it.

Now the only reason I can think this is happening is because when the log agent starts up on boot, there is no X session open, however it still does not work when I log in, maybe because the log agent is running as root, and I am logging in as a different user. Is there any way to make the Java Screen Capture Robot, just take screenshots of the default X11 session of the person who is logged in?

Many Thanks

Sambo