[jsr-314-open] Ajax validation

[Dan Allen]

On Mon, Jun 22, 2009 at 2:32 PM, Andy Schwartz <andy.schwartz at oracle.com>wrote:

> Andy Schwartz wrote:
>
>> Thanks Pete -
>>
>> Pete Muir wrote:
>>
>>> The issue is that it isn't always (normally IMO) the case that you want
>>> the model update on an ajax request to do validation, you only want the
>>> model updated when you actually hit submit... This is a problem if you are
>>> applying values directly to the managed JPA entities which get flushed to
>>> the database at the end of the TX.
>>>
>>>
>> What are the consequences of applying a validated value to a managed
>> entity early - ie. during Ajax validation, as opposed to waiting until the
>> full submit?  Is there some overhead here that you want to avoid?
>>  Presumably the value is not being flushed to the database immediately (as
>> you said, this won't happen until the end of the TX),
>>
>
> Oh, actually... So is the deal that your are committing the TX in response
> to the Ajax validation, and thus the value is actually being flushed to the
> database immediately?


That's correct. The flush (i.e., database update) is avoidable by
sidestepping a transaction or using a JPA vendor extension such a
Hibernate's manual flushing, but the concern is that it is too easy for a
developer to inadvertently cause a database update by adding Ajax w/o
changing backend code.

The whole "skip the update model" aspect of validation is really worth
debating in a separate thread. The counter argument to using it is that
cross-field validation becomes very awkward because you have to retrieve the
converted value from the component rather than from the model property
(throwing a wrench in more advanced Bean Validation usage as well). But
let's venture down that discussion in a separate thread.

As far as I know, ICEfaces does not support the "bypass model update" when
using partial submit. I've discussed this with Ted, but I don't thing
anything ever came of it.

-Dan

-- 
Dan Allen
Senior Software Engineer, Red Hat | Author of Seam in Action

http://mojavelinux.com
http://mojavelinux.com/seaminaction
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