Since I just hit my head against the wall for a couple of hours, I'll see if I can spare others the trouble. (Cudos to Janne for hints on this one.)
Problem:
You want to generate dynamic graphics in a command line app or a servlet in unix, never actually displaying anything. You get a "connection to X11 server refused" error, because an X server is not running or you don't have permissions to access it.
Solution:
JDK1.4:
start Java with -Djava.awt.headless=true
See http://java.sun.com/j2se/1.4/docs/guide/awt/AWTChanges.html#headless
Older JDK's:
See if you can install xvfb, a virtual X server, made for nasty
software just like AWT-based Java. Or, see if you can use PJA,
http://www.eteks.com/pja/en/index.jsp.
Argh. I HATE AWT!
Text by ebu.