[ovirt-devel] hibernate's internal PersistentBag sent to FE

[Alexander Wels]

On Monday, June 01, 2015 09:08:50 AM Tomas Jelinek wrote:
> Hey all,
> 
> since the org.ovirt.engine.core.common.job.Job/Step... has been moved to use
> the JPA we have a problem on frontend. The problem is that the @OneToMany
> annotations results in a List which is of type PersistentBag. When we send
> this to Frontend it fails during deserialization. It actually fails quite
> bad because the FE already has an ui-override of it which is not correct
> resulting in a ton of NPEs in development mode.
> 
> So, there are 2 nasty fixes I have made where none of them should be merged
> but demonstrate the possibilities: 1: extend the FE to be able to work with
> the PersistentBag (https://gerrit.ovirt.org/#/c/41682/) not really good
> solution since the PersistenBag is an internal Hibernate class which is
> really not meant to be passed around
> 
> 2: fix on the backend to not send the PersistentBag but an ArrayList. This
> is only a PoC fixed on a command we face the problem
> (https://gerrit.ovirt.org/#/c/41797/) Obviously this is not going to work
> for other commands accessing the same Job nor for other entities.
> 
> So, the first option is generic but very very bad. The second option should
> be used but not sure how to do this in a cheep way (e.g. without using
> reflection to deep traverse everything sent back to frontend checking if it
> does not have a PersistentBag in it.
> 

Tomas,

Thanks, I was investigating the same issue, I noticed it last Friday just 
before leaving, so I was investigating the problem to see what was going on. 
You are right we should not be sending PersistentBag to the frontend at all. 
So how about we do a combination of [1] and [2], but instead of delegating in 
[1] we actually simple throw an exception stating don't sent PersistentBag to 
the front end. that way anyone inadvertently using it will be notified 
immediately (since their code won't work).

Alexander

> Any better ideas?
> Thanx,
> Tomas
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