Authenticating a GWT application in Joomla

I have a GWT application that I would like to integrate with the Joomla login system. Everytime an AJAX request is sent to the server, the application should check that the user is authenticated (username and password pass)

Any ideas of how to implement this?

I had these ideas but don't like them for the reasons mentioned:

• Ask the user for there开发者_如何学运维 username and password (again...) and then save it in a cookie. (Security is an issue and I have to ask them for the username and password after they have already logged into the main joomla system.
• Save the username and password in a PHP session variable. (This might work but what would happen if the sesson timed out, the user may take some time configuring the GWT data structures, so it would not be nice for an error like this to occur).

Does anyone have better ideas?

Will users be authenticating against the GWT application? If so, you might want to create an Authentication plugin for Joomla that backfills users from GWT into Joomla.