how i can redirect (without loosing session) to a full url from jsp page in struts.

Hi
Thank you for reading my post
I have a problem.
problem is :
I should go back to last visited page after my user login or changed locale or ..
i can retrive las visited page : by using request.getheader("Referer")
and i store it into a session variable.
No after my user loged in i should forward?redirect? or sending him/her back to that url
without loosing his/her session
Problem is : its a full url and i just can redirect ro a sub url in my context? (pleas correct me if i am wrong)

how i can send my visitor back to thier page which i stored in session ?
for example is there any tag in jsp or struts for it?

Thank you