You don't need prior knowledge of Struts 1, but you do need to know OOP and Java. Knowing the Servlet API is definitely a plus even though a Struts programmer rarely has to write a servlet anymore. JSP is optional because Struts 2 supports other technologies for the view.
New rule: no elephants at the chess tournament. Tiny ads are still okay.
a bit of art, as a gift, that will fit in a stocking