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From "Carsten Ziegeler" <cziege...@s-und-n.de>
Subject RE: FragmentExtractor getting and releasing Store every time?
Date Mon, 02 Jun 2003 10:40:29 GMT
Torsten Knodt wrote:
> On Sunday 01 June 2003 15:51, Carsten Ziegeler wrote:
> CZ> The safest way is to lookup/release a component every time you
> CZ> need it, so the fragmentextractor uses the "correct" approach.
> CZ> If you know that the component you want to use is ThreadSafe
> CZ> and will always be ThreadSafe than you can optimize your code
> CZ> and lookup the component only once - this optimization has been
> CZ> done in the xslttransformer.
> XSLTProcessorImpl uses Store.TRANSIENT_STORE, like the
> FragmentExtractor. I
> haven't mentioned this explicitly.
> I have looked into the interfaces, and when I understand right, I
> had to look,
> if store implements ThreadSafe. Store doesn't implement
> ThreadSafe, but the
> MRUMemoryStore, which is used as default in cocoon. So I'd say
> it's a bug in
> XSLTProcessorImpl. Agreed? What I would do, is asking in avalon-users for
> changing XSLTProcessorImpl and perhaps others or to have Store implement
> ThreadSafe. But I guess, Store is already released.

We have to distinguish between the component (it's interface) and the
implementation. The interface should never expose details about the
implementation, so an implementation detail like ThreadSafe etc. is
not part of the interface which in this case is Store.

However, the implementation "decides" if it is thread safe, poolable
or whatever.

Now, the optimization I was refering to can only take place *if* you
know which implementation for a component is really used and *if*
this specific implementation is ThreadSafe. This is a dangerous
assumption! If you assume a component is implemented in a thread safe
manner and this changes sometime and you don't reflect these changes
than you will quickly result in threading problems.

Carsten


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