What is DynaActionForm? Ref Url :
Suppose we have lots of JSP pages with forms that we want to validate. We could write an ActionForm with getter/setter pairs for each of the JSP pages, but, if we had 20 pages, we would have to write an ActionForm for each one. This is inconvenient.
Instead, we can create a single DynaActionForm. A DynaActionForm can be reused in any number of Actions. A DynaActionForm will list all possible properties with their types that can appear on a Jsp page. This will become more clear as we actually start creating the DynaActionForm.