[Russell, please review and add to FAQ?]
Q: How does Axis create my backend service objects? Can I control this? A: Axis supports a "scope" parameter on services, which can be set to "request" (make a new object to service each request - this is the default), "session" (associate a new object with each session), and "application" (all users share a singleton object). WARNING: If you set the scope to "session" or "application", it is possible that multiple threads of control may attempt to access your object's methods at the same time. It is your responsibility to ensure that your objects are thread-safe in these cases. Q: So does Axis support sessions? A: Yes. We have a session abstraction which allows an extensible set of underlying implementations - take a look at the class org.apache.axis.session.Session for details. In particular, we currently support sessions based on HTTP cookies and also transport-independent sessions based on SOAP headers. It is up to some handler on the request chain to set up an appropriate Session implementation and attach it to the MessageContext with MessageContext.setSession() so that anyone who wants to use session semantics can get at it. Q: Cool, SOAP header-based sessions? How do I make that work? A: There is a Handler class called "org.apache.axis.handlers. SimpleSessionHandler" which implements this functionality. You need to include this handler in the request and response flows of both your client and your server. Take a look at our session test (test.session.TestSimpleSession) for an example. Q: What else can I do with sessions? A: Any time after the session context has been established, calling getSession() on the current MessageContext will obtain you a reference to a Session object. You may use this object like a Hashtable to store arbitrary data associated with this Session. For instance, on one request you might extract the caller's name and address from a database (an expensive operation), and then cache them in the Session object for fast access on subsequent invocations from the same caller. This functionality can be used either by custom Handlers or by your backend service object itself. --Glen
