Re: [Springframework-developer] Potentialt dangerous hibernate Session reuse

[Colin S. <col...@ex...>]

Per Olesen wrote:

> Nick Minutello wrote:
>
>>>> Hence, one web request will quickly
>>>> use many connections, at the same time.
>>>
>>
>>
>> How so? Why should there be more than one session for a given request?
>>
>
> If the web-layer of the application calls multiple methods into the 
> services layer where each method performs hibernate work, a new 
> session will be opened for each hibernate call. That is of course, if 
> "defferred close" is set on the filter.
>
> Isn't that how it works? At least, that was what we experienced when 
> we tried it.

Yes, that's exactly how it would work, if you did indeed call down into 
the tx wrapped service layer multiple times. Of course, it's usually not 
appropriate to combine data from multiple transactions anyway, but one 
common case of this is where you call down to get the form backing 
object contents, and then later call down again with the modified 
object. The deferred close strategy blows up in this scenario. One 
workaround which Spring MVC makes pretty easy is to keep your form 
backing object in the session session, from the previous get. Then you 
end up only doing one call down into tx layer to apply changes.   But 
this _is_ a limitation, of course.

Colin