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From Antonio ForniƩ <>
Subject Re: The need for pooling beans
Date Wed, 04 Nov 2009 14:07:10 GMT

Thank you for your reply. By the way two comments:

Quintin Beukes-2 wrote:
> I'm not sure if the same applies to calling different business methods on
> the same
> SLSB, though I don't think it does.

It does. It's not possible that two clients are using the same SLSB at a
time, even if they're using different methods. Imagine what would happen if
method B was called inside method A and two clients were using methods A and
B of the same instance.. they could end up in the same method of the same

Quintin Beukes-2 wrote:
> ...if 2 clients request to invoke the same business method on the same
> bean
> at the same time, one will be served first, while the other will block.
> When
> the first one returns the 2nd caller will be released to invoke the
> method.
> The pooling of SLSB is to avoid this, so with a given pool size of X you
> can
> have X concurrent business method invocations for any given bean...

Yes, that's true. And I understand this idea in case of, for example, DB
connection pooling: a)Connetions are created before your request them and
you reuse them. b) There will never be two clients trying to use the same
connection. c) There SHOULD never be a client waiting for other clients to
release a connection.

But why to use bean pooling for a Session Facade (implemented with a SLSB)?
We can't assure that two clients using the same method of a service bean
will bring problems. In fact, that's the idea behind servlets: only one
instance per servlet. Clients use the same servlet instance at a time. Of
course there will be cases where it's good to ask for a new instance of a
bean (or create it or whatever), for example, when we know we have
not-shareable resources, like an instance variable that is a DB connection.
But that's not to assume that EVERY SLSB has to be pooled. It may bring more
handicaps than advantages...

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