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.
I think it would be easier to rewrite your servlet class so that you can instantiate it, and call the relevant methods directly from within your web service. That would save all the overhead of transforming Java objects to HTTP back to Java objects, as well as avoiding the problem you ask about.