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From Dain Sundstrom <>
Subject Re: Some jpa questions
Date Thu, 24 Aug 2006 23:10:14 GMT
On Aug 24, 2006, at 1:50 PM, Andrus Adamchik wrote:

>> 2. What's supposed to happen when you try to use a CM tx scoped EM  
>> outside a JTA tx?  Section 5.6.1 seems to imply we aren't supposed  
>> to just throw an exception, but section 5.9.1 seems to imply there  
>> is no provider EM in back of the CM EM to do any work without a  
>> JTA tx.  Are we supposed to create and close a provider EM for  
>> each call outside a tx?
> Good question... I have no idea.

 From what I understand, yes.

>> - How heavyweight are EntityManagers?
> I guess this could be implementation specific, but they are  
> lightweight in Cayenne, and I assume they are lightweight in other  
> providers as well.
>> Is it more efficient to create a new one or pool them?
> While the spec provides some leeway (see below), container with  
> pluggable provider has no way of knowing the best strategy. My vote  
> is to avoid pooling EntityManagers by default.

+1 If it later becomes an issue we can introduce pooling.

My guess is that most providers are pooling under the covers since  
the largest user group will be unmanaged servlets which don't do app  
level pooling.


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