This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
You need to draw your graph with whatever you like, and find library that will convert your graph to gif, jpeg or png. Actually I used servlet to draw, convert and serve the image, and in the JSP include it as: