Nice. Elegant little bit of code. I'll have to update my version.
WILL
----- Original Message -----
From: "Nathan Bubna" <[EMAIL PROTECTED]>
To: "Velocity Developers List" <[EMAIL PROTECTED]>
Sent: Friday, January 30, 2004 7:51 AM
Subject: Re: [veltools] session tool init and synchronization
> Claude Brisson said:
> > Three times in a row, in this 4-mails long thread, I thought of an
answer,
> > began to write it down, just to discover than Nathan or Will had just
posted
> > exactly what I wanted to say.
> >
> > You guys are fast !
>
> :)
>
> > Still, my opinion :
> >
> > 1. the mutex synchronizsation, as proposed by Will, is not only
desirable
> > but mandatory : session tools are not so rare, especially for webapps
that
> > provide authentification. Several instances of the same session-scoped
tool
> > can then lead to very strange side effects (I encountered the problem
with a
> > session-scoped upload tool that remembered the current directory under
the
> > root of the loggued user).
>
> really? hmm. part of me wants to just dismiss this as a poorly designed
> webapp/tool, but a little synchronization once per user isn't too much to
ask.
> ounce of prevention, pound of cure, yada yada yada. ;)
>
> > 2. to be rigorous, I would suggest the following synchronization method,
> > which I think is the only clean way :
> >
> > public Object getSessionMutex()
> > {
> > Object ret = session.getAttribute(SESSION_MUTEX_ATTRIBUTE);
> > if (ret == null) ret = createSessionMutex( );
> > return ret;
> > }
> >
> > public void synchronized createSessionMutex( )
> > {
> > // check again it doesn't already exist
> > if (session.getAttribute(SESSION_MUTEX_ATTRIBUTE) == null)
> > session.setAttribute(SESSION_MUTEX_ATTRIBUTE , new
Object( ));
> > }
> >
> > There is no performance drawback at all.
>
> except that whole "not compiling" problem. ;) i'm guessing that for the
> second method you meant:
>
> public Object synchronized createSessionMutex() {
> Object o = session.getAttribute(SESSION_MUTEX_ATTRIBUTE);
> if (o == null) {
> o = new Object();
> session.setAttribute(SESSION_MUTEX_ATTRIBUTE, o);
> }
> return o;
> }
>
> and yeah, i think that'll work! thanks for the tip!
>
> Nathan Bubna
> [EMAIL PROTECTED]
>
>
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