The application I want to crawl is built using Struts and JRun.
This should be simple with Offline Explorer Pro. Simply browse to the site logon page in Offline Explorer Pro`s Internal browser, enter your username and password (or another info, if the form requires) and then press and hold down Ctrl + Alt keys while submitting the HTML Form. Offline Explorer Pro will create a new Project for you with the recorded HTML Form contents, so it will submit the form automatically when you start downloading it.
I hope this helps.