[news.eclipse.rt.eclipselink] Re: in memory rollback

[tbee <tbee@xxxxxxxx>]

Gordon Yorke wrote:
> I don't see how SQL would solve your problem.  You have user requested 
> changes to Entity instances that are not valid.  You will need to 
> develop some mechanism in your application to notify the user and 
> refresh the user's view.  EM.refresh() can rollback the changes to the 
> Entities within the Persistence Context if that is all you need.
> --Gordon

Not quite. I have user made changes and system made changes (based on the user changes), I only need to rollback the latter. By using SQL for the system changes, I can use the database rollback to roll that back, while keeping the user made changes in memory.

Say there is a "transfer" entity moving 10 dollars from account A to account B. That is the instruction: "this must happen". Now the system starts actually implemeting that order, resulting in an "substraction" entity on account A and "addition" entity on account B. The addition may fail and both have to be rolled back, but the transfer entity should remain in memory. I cannot have a "transfer" entity in my system, without corresponding sub and add.

An approach would be to mark a transfer as "unbooked", store it, commit, and only then start creating the sub/add entities. Upon success the transfer is marked "booked" and all is committed, or on fail you can indeed clear all entities. That may work.


Tom