Accepted and Agreed
Bob Lee
<crazybob@CRAZYBO To: [EMAIL PROTECTED]
B.ORG> cc:
Sent by: A Subject: Re: synchronized
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12/25/02 08:54 PM
Please respond to
Bob Lee
> <BOB>Actually, you're not supposed to use synchronization primitives to
> synchronize the execution of multiple instances, as the bean may be
> deployed in multiple VM's. This is not the case in the example below.
> Actually, there will never even be contention for the lock below. The
> same goes for statics.</BOB>
>
> Kindly Elaborate
Singletons are a good example. If you are truly only supposed to have one
instance for the entire application, simply synchronizing access to a
static
field will not work. You will have an instance for each classloader
(potentially multiple instances per VM). In the same way, if you're
supposed
to synchronize access for some resource for the entire application or
across
multiple bean instances, synchronization primitives obviously won't work as
the instances may be running in different VM's.
If you only need to synchronize locally, as is the case in the original
author's example, go ahead.
Another reason not cited by the specification could also be to prevent long
critical points and deadlocks, however the rules and best practices here
aren't different from any other application, EJB or not.
The EJB architecture tries to insulate us completely from worries about
synchronization or threading, and it's successful to an extent, but the
fact
is that there are some things it can't or shouldn't hide, IMO.
Thanks,
Bob
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