How to reset the data when the session lost?

Question

When I use response.sendRedirect("http://localhost:82/main.jsp")
the session lost, because the URL before redirect is using SSL,
"https://localhost:81/index.jsp", they use the different port,
so the session lost, what should i do to prevent this? And how
to reset the data?

Answer 1

Create a HashMap and store it as an attribute of the servlet context. In the first servlet assign the user a key and store all session data in the HashMap under that key (use a vector, collection or user defined class).
In the response.sendRedirect call add the key to the url:
response.sendRedirect(url + "?key=" + userKey);
In the second servlet get the key (request.getParameter("key")), retrieve the session data from the HashMap in the servletcontext and store in an httpsession.
Remember to delete the entry from the HashMap so it doesn't become overly large.