[jsr-314-open] Ajax validation

[Pete Muir]

On 22 Jun 2009, at 19:51, Dan Allen wrote:

> 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.

Yeah, there is no decent, standard, way to do this.

>
> 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.

Yes, this is definitely worth considering as well - Alex and I hadn't  
thought of that aspect I guess.

>
> 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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>
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