Hi,It's not a silly question ... this is an issue that *lots* of people don't understand.
It might be a silly question... but curiosity...
Why we need to synchronize at all? Each user session will be unique in the server and so the extracted variables from that session.
KP
It is trivially easy for a single user (inside a single session) to submit multiple simultaneous requests. How, you might ask? Here's just a few of the possibilities:
* User submits a form, presses STOP, and submits the form again.
* User requests a page that has one or more <img> or <object> elements with URLs pointing in to the same webapp -- most browers will perform multiple simultaneous requests to retrieve the necessary data.
* User requests a frameset page ... the browser will typically perform simultaneous requests for the individual frames.
The net result is that application developers *must* assume that thread safety is an issue for access to session scope attributes, and must employ synchornization as needed to avoid problems. Note that it's not an issue of whether the HttpSession.getAttribute() call is safe -- the servlet container takes care to ensure that this is always OK -- it's an issue of what accesses you do on the attribute after retrieving it that matter.
Craig McClanahan
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