Will Glass-Husain said:
> I can't comment on whether or not the synchronization should occur (not
> being a regular Tools user), but I hit this problem in a project and got
> stung when I falsely assumed you could synchronize using the session object.
> This was a particular concern for me with web apps using frames, as the
> multiple frames will simultaneously make HTTP requests. My experience was a
> classic intermittent failure problem where the system worked on my dev
> server but not on the client's server-- a very frustrating debugging
> experience.
yeah, that's no fun.
> The solution was to make my own simple session mutex, and then synchronize
> on that object. Maybe this could be useful.
i thought about just doing something like this too, but i'm not sure it's a
totally secure method either. i'm by no means an expert in
threading/synchronization issues, but what about a two-thread scenario
where...
> /** Get an object that can be synchronized across a session. */
> public Object getSessionMutex()
> {
where thread #2 gets to the following line:
> Object ret = session.getAttribute(SESSION_MUTEX_ATTRIBUTE);
> if (ret == null) {
> ret = new Boolean(true);
while thread #1 is still in here and hasn't yet set the attribute
> session.setAttribute(SESSION_MUTEX_ATTRIBUTE,ret);
> }
> return ret;
> }
>
> You can then use this with:
>
> Object mutex = getSessionMutex();
> synchronized (mutex) {
> some code
> }
granted, your example would certainly be far more effective than synchronizing
on the session object, and in practice i'd imagine it would be *very* unlikely
to ever fail. but it seems to me that this could still theoretically fail.
or am i missing/misunderstanding something?
Nathan Bubna
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