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From Jim Talbut <jtal...@spudsoft.co.uk>
Subject Re: Audit log with OpenJPA
Date Thu, 14 Jul 2011 05:40:31 GMT
On 13/07/2011 21:14, Pinaki Poddar wrote:
> Yes. Any audit facility needs to have a snapshot of the entity when it
> entered a persistence context, so at @PreUpdate or at any other time points,
> it can figure out what has essentially been changed about that entity in a
> transaction. Now either one can build their own mechanics to store the
> original state of the entity or can use OpenJPA's own facility to access the
> original state. The blog article showed the later approach.
I also went with using the OpenJPA stored version of the original object.
There are a few niggles to getting that data that one has to work with, 
but I still think it's considerably less effort than building your own 
mechanism.
> Secondly, in my view, an audit facility should be orthogonal. The actual
> domain entity need not know that it is being audited. Thereby, the domain
> entity need not have an association or knowledge of an Audit object.
I'd agree with that for a general purpose audit facility.
In my case I don't even call it "audit" it's change tracking, and the 
change information is displayed alongside the entities in the most 
common cases.
> Thirdly, the audit facility should allow the audit information be stored in
> a separate database, in the same database or may even be logged in a file.
> That is to say that persistence of audit information should be decoupled
> from persistence of the domain objects.
Again, true for a general purpose audit facility.
If you want to be really secure the audit log should be sent directly to 
a printer :)

> If you intend to store audit information as a persistent entity in the same
> database as the domain entity, then the simple solution is something like
> this in a domain class:
>
>    @PreUpdate
>    public void audit() {
> 	  Audit audit = new Audit();
>            // now populate audit information
>            // .... some serious delta computation
>
>            // Now get the entity manager that is managing this current domain
> object
>            OpenJPAEntityManager em =
> OpenJPAPersistence.getEntityManager(this);
>
>            // And persist the audit information in the same transaction
> 	  em.persist(audit);
>    }

I wonder if that bends the rules any more than my approach?

Jim

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