Re: Envers-style Auditing in DataNucleus?


I would suspect non RDBMS would also be supportable.  Concept being that each time an object is modified, the dirty fields of the given object (before and after) are persisted in a document/table, with any custom contextual information that can be provided to the persistence manager.  

Envers essentially provides this behaviour by creating separate tables in a different connection/database to track changes to given entities.  I realize that JPA/JDO do not specify any of this, but was wondering if there was an easy way to create/implement something like this with DataNucleus.  I would essentially see if as putting a listener on the 'commit' phase, checking for dirty fields, and persisting the change of the fields with the object identifier in a table/document.  My immediate use case is RDBMS, but NOSQL could be interesting to support as well.

My problem is multi-fold.
1) I'm not sure how to put a listener on any 'commit'.  Rather, there seems to be separate listeners for 'create', 'update', 'delete'.
2) Once the listener triggers, I'm not sure how to retrieve which fields are 'dirty'.  I see there is a `JDOStateManager`, but not sure how to access it from an `InstanceLifecycleEvent`.  I suspect it must be from a `getPersistentInstance()` but I cannot seem to find a helper method anywhere that retrieves a `JDOStateManager`.
3) Even once I am able to get the dirty fields via the `JDOStateManager`, I do not know how to retrieve the original value of the field without needing to re-read the object from the DB

Any suggestions would be greatly appreciated.



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