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.
I’ve looked at a lot of different solutions, and in my humble opinion Aspose is the way to go. Here’s the link: http://aspose.com