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.
The data posted typically comes from a browser, and the browser doesn't know anything about 'objects'
It is possible to set up applet-servlet communication, but typically the objects are sent (via an object stream) to the client rather than the other way around. I see security issues in accepting object data from clients.