[wildfly-dev] Favour jboss-persistence.xml if present

[Jason Greene]

> On Jan 29, 2014, at 3:33 PM, Scott Marlow <smarlow at redhat.com> wrote:
> 
>> On 01/29/2014 04:24 PM, Brian Stansberry wrote:
>>> On 1/29/14, 3:20 PM, Scott Marlow wrote:
>>>> On 01/29/2014 03:17 PM, Jason Greene wrote:
>>>> 
>>>>> On Jan 29, 2014, at 2:11 PM, Scott Marlow <smarlow at redhat.com> wrote:
>>>>> 
>>>>>> On 01/29/2014 02:44 PM, David M. Lloyd wrote:
>>>>>>> On 01/29/2014 01:39 PM, Klein, Christopher wrote:
>>>>>>> Hey guys,
>>>>>>> I already filled out a feature request in JIRA (https://issues.jboss.org/browse/WFLY-2816).
>>>>>>> 
>>>>>>> We have the situation that our development environment (currently JBoss AS 7.1.1) differs from the production instance (WebSphere 8.5). Our persistence.xml has to be adjusted for production environment: different jta-data-source, different properties. The dirty solution for this problem would be to generate separate build artifacts for both environments. As you can imagine I don't like the idea of having two binaries just because of a few different settings. Other options (WildFly or WebSphere specific JPA properties; extending Hibernate persistence provider) do not work.
>>>>>>> 
>>>>>>> A much nicer solution would be: WildFly checks on deployment process for the existence of a jboss-persistence.xml. If it does, the jboss-persistence.xml is used for configuring the JPA subsystem. Otherwise it falls back to the standard persistence.xml. The jboss-persistence.xml would use the XML schema from persistence.xml.
>>>>>>> 
>>>>>>> I lookup into the WildFly sources and this change should be an easy patch which I would provide.
>>>>>>> 
>>>>>>> So here are my questsions:
>>>>>>> 1. Are you generally interested in accepting such a pull request or is it a feature you don't want?
>>>>>>> 2. Does another solution exists to my problem apart from generating different artifacts which makes this pull request needless?
>>>>>> 
>>>>>> It sounds like a reasonable idea that actually applies generally.  If I
>>>>>> recall correctly, we have something of a mix today of descriptors which
>>>>>> override versus supplementing existing configuration.  But overall the
>>>>>> unofficial policy for new descriptors has been to add them in to
>>>>>> jboss-all.xml as subdescriptors, FWIW.
>>>>> 
>>>>> I'm not sure that jboss-all.xml would be a good place for the
>>>>> persistence unit definitions.
>>>> 
>>>> I would agree that this is probably impractical.
>>>> 
>>>>> 
>>>>> I think that the proposed jboss-persistence.xml (or
>>>>> wildfly-persistence.xml) could be helpful for anyone that wants to only
>>>>> develop on WildFly but deploy on other application servers.  I suppose
>>>>> this could help someone that wants to migrate off of WildFly as well (to
>>>>> prepare for a switch to something else).  Is that what you mean by the
>>>>> proposed solution applying generally?
>>>> 
>>>> It does sound a lot like a vendor specific alt-dd feature. We have some other solutions as well that might be relevant:
>>>> 
>>>> 1) Deployment overlay feature - This allows you to override the descriptors in a deployment without modifying the deployment. These are added in a separate management op with a match pattern, and preserved outside the lifecycle of the deployment. Available in WildFly 8 and EAP 6.2 (can’t recall if it made EAP 6.1).
>>> 
>>> I was just reading
>>> https://docs.jboss.org/author/display/WFLY8/Deployment+Overlays but I'm
>>> not sure that would help with this use case.  Since the deployment will
>>> fail due to the persistence.xml targeting WebSphere (persistence unit
>>> property "hibernate.transaction.manager_lookup_class" is set to
>>> "org.hibernate.transaction.WebSphereExtendedJTATransactionLookup").
>> 
>> The persistence.xml that is the deployment overlay would not include
>> those settings. The deployment overlay feature hides the original
>> persistence.xml in the deployment archive from the deployment
>> processors; they only see the overlay.
> 
> Thanks Brian, I missed that the deployment overlay is created before 
> deploying.  So that could help someone crack open an archive and replace 
> the persistence.xml with one that will work.

Right exactly. The disadvantage is every update to the descriptor requires an updates overlay.

Just thinking out loud that we could do a proprietary alt-dd thing in jboss-all.xml where we allow you to set replacement names. E.g web.xml=other-web.xml etc.

Then we just parse this before anything else and it would apply AFTER overlay.


> 
>> 
>>> What might help is if we could ignore (or auto-magically remove during
>>> deployment) certain persistence unit property settings that we know will
>>> cause the deployment to fail.
>>> 
>>>> 
>>>> 2) Property Substituion - There is a flag you can optionally enable in standalone/domain.xml that allows descriptors to contain property expressions. However, this only works for this use case if all venders are using the same expression language (unlikely). I just thought I would mention it.
>>>> 
>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
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>>>>> wildfly-dev at lists.jboss.org
>>>>> https://lists.jboss.org/mailman/listinfo/wildfly-dev
>>>> 
>>>> --
>>>> Jason T. Greene
>>>> WildFly Lead / JBoss EAP Platform Architect
>>>> JBoss, a division of Red Hat
>>> 
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