Sakai Sessions and UsageSession

Having just been looking at these for a little while I thought I'd document them a little. The basic setup is that the Sakai Session is your session with the application and is very similar to a HttpSession. Your Session is setup for each request by the Sakai RequestFilter. The UsageSession on the other hand is your logged usage of the application amd is mainly there so that you can enumerate all the active UsageSessions. The UsageSession is actually store in the Session and is mainly used for presence.

However just to confuse things a little the UsageSessionService (manages UsageSessions) has some very important methods, login() and logout(). These setup and destroy your Session and UsageSession at the same time. Login tools in Sakai should call UsageSession.login() to setup the Sakai session with the authenticated user details.