On Jun 9, 2004, at 2:47 AM, Marko Kocic wrote:
>> On Jun 8, 2004, at 11:40 AM, Marko Kocic wrote:
>>> No, I don't put DataContext in session/visit, I just fetch it for
>>> service method invocation (see interceptor bellow).
>> This may have undesirable side effects. If you want to work with
>> relationships, related objects must be registered with the same
>> DataContext. Of course you can fetch all needed objects on every
>> request, but this seems wasteful. The most efficient use of Cayenne in
>> a web app is when a DataContext spans the whole session.
> Thanx for insight. I just wanted to use DataContext the same way I used
> Connection, fetch it from DataSource when I need it, use it, and close
> when I don't need
> it anymore.
DataContext is different from Connection, DataSource, etc. I discussed
it a bit in the TSS article. That's the beauty if it - you don't have
to "close" or otherwise "manage" it.
> Sure I want to use relationships. So you suggest I should have one
> DataContext per user for performance reasons? What if I have say 500
> logged in users?
> Does each DataContext maintain its own object cache, or cache is
> shared between
> contexts? I'm concerned about memory.
This a common tradeoff of any caching system - memory vs. speed. You
can tweak it though. When memory becomes a problem (Never been a
problem for me yet), you can clean up DataContext cache, or set it to
null conditionally (not on every request, but in places where you want
to do cleanup).
> I'm still playing with Cayenne, so IMHO something like "best
> practices" info
> would be great.
Things about DataContext are all in the user guide, and Tapestry/Struts
tutorials. There is always room for improvement of course...
> btw [off topic]
> Cayenne is a great framework (at least what I found so far). Modeler
> is what
> bought me to
> Cayenne :). But it stll has some (non technical) issues where it is far
> behind hibernate. Just
> look at the hibernate site, it's full of examples and tutorials (h +
> spring, h + webwork,
> h + tapestry, h + struts, h + BMP beans, h + jboss...).
We provide Tapestry, Struts and (primitive) JBoss/Session EJB examples.
But I agree that we need more. The thing is, myself and other Cayenne
committers may not be the best experts in every single framework
available out there. For instance I am using Cayenne/Tapestry and
hardly need EJB for anything at all. We need more community help!
So please (and this is a request to all Cayenne users), when you use
Cayenne in some new environment, or think you've discovered some
patterns not mentioned in the docs, submit a simple example via this
list or our bug/feature tracker. This will help others immensely!
Marko, your HiveMind examples is a very good start. I am sure you'll
have it updated and extended when you start using Cayenne on the actual
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