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.
In servlets , HTTPServletRequest's getParameterNames() and getParameterMap() would give you the expected parameters list.
For Struts , you can access HTTPServletRequest as well , so that should be acheivable. anyways wait for Struts experts comments.