[hibernate-issues] [Hibernate-JIRA] Commented: (HHH-3887) Envers hbm xml based configuration

[Helmut Pasch (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/HHH-3887?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=40067#action_40067 ] 

Helmut Pasch commented on HHH-3887:
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Yes, it would be. The approach Envers uses to audit entities is a good one.

I lately explored Spring DATA JPA.This Spring Project also aims to auditing entities. I was indeed a little bit surprised they announced this feature being implemented by AOP. Looking a bit closer I discovered that every entity must inherit from a generic Class called Persistable<ID>. Well, I couldn't bring this together AOP and inheritance are still two different things.

I would categorize Envers as a technology based on AOP technologies. The good thing about this is, that AOP technologies enable us to extract (mainly technical) aspects out of the plain POJOs. The POJOs will stay as much complex as your problem domain demands it. Coming back to the Spring approach, especially inheritance is a feature, we only want use for abstractions within our problem domain, not for technical problems.

To emphasise this we are very happy with Hibernate and we also adapted Envers. We are still looking forward to having sometimes this xml based configuration feature.

To point that out, XML based configuration is very well suited for ORM. This way we could cleanly extract the technically aspects, the persistent aspect and (more or less technical) the auditing aspect, from our POJOs. To explain our our understanding: "JSR 303: Bean Validation" is a feature were we appreciate the annotation based approach. In this case the capabilities of the domain model (the POJOs) to build better comprehensive abstractions are really improved. Looking back to the annotation based approach of Envers, we see it more like a burden to handle the aspect within the code.
In some project this burden evolve to a real show stopper. We are still interested in (programmatically) manipulation and reconfiguration of the auditing aspect, in XML it would be very fine and easy to do this.

> Envers hbm xml based configuration
> ----------------------------------
>
>                 Key: HHH-3887
>                 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-3887
>             Project: Hibernate Core
>          Issue Type: Improvement
>          Components: envers
>    Affects Versions: 3.5.0.Beta-1
>         Environment: Hibernate: All Hibernate Versions including Envers as subproject
> Our Project: Hibernate 3.3.1, Spring 2.5.6, Spring DM 1.2.0, Swing, GWT, ....
>            Reporter: Helmut Pasch
>
> Currently the tool library Envers can only be configured / mapped to java POJOs by annotations. We would appreciate if this mapping could be done by hbm xml files. Using this approach the  POJO won't be bound to Envers annotations. They simply would be left as POJOs instead of transformed to JPA like Entity Beans.
> We use POJOs to directly serialize  them to a client tier, e.g. a Swing or GWT client tier. If our POJOs have to rely on Envers annotations similar like JPA annotations we see only two options objects may leave the server tier. First by a copy to an annotation less value object, which is consuming performance and resources. Second by coping / using Envers / Hibernate libraries for reference purposes on the client tier.
> Both solutions are not very attractive compared to the very well working hbm xml approach Hibernate core ORM functionality provides us. It is our intention to reduce / eliminate in client server communication model transformations like coping objects or transforming them to other formats like XML, e.g. like web services does. The easiest way would be to just serialize the Java POJO objects. But never then less the client should only depend (logically) on the server API. It is not intended to rely on a specific server implementation.

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