This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
I'll give you the answer I give my clients when they ask if something outrageous is impossible.
"Sure it's possible, but it's going to cost you!"
In order to do this outrageous and completely unnecessary thing, you'd have to extend the Struts ActionServlet to read a database instead of an XML file. Since Struts is open source, you could obtain the source and figure out what needs to be modified in order to do it.