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Virtual columns (@Formula of Hibernate) [message #500349]

Wed, 25 November 2009 12:41

Eclipse User

Hi!

Does anybody know if EclipseLink has an equivalent to Hibernate's @Formula ( http://docs.jboss.org/hibernate/stable/annotations/reference /en/html/entity.html#d0e2273)?

I would like to automatically populate the "currentPrice" attribute of a "Product" entity with the price valid for today which has to be reat from another database table.

Re: Virtual columns (@Formula of Hibernate) [message #500532 is a reply to message #500349]

Thu, 26 November 2009 09:36

Eclipse User

There is no direct equivalent (please log an enhancement), but depending on what you want to do, there are ways to accomplish the same thing.

EclipseLink defines a TransformationMapping which can map a computed value from multiple field values, or access the database.

You can override the SQL for any CRUD operation for a class using its descriptor's DescriptorQueryManager.

You could define a VIEW on your database that performs the function and map your Entity to the view instead of the table.

You can also perform minor translations using Converters or property get/set methods.

Re: Virtual columns (@Formula of Hibernate) [message #500637 is a reply to message #500349]

Fri, 27 November 2009 04:27

Eclipse User

Hi James, thanks for your hints. I think I can do what I want with one of the options you mentioned, I just have to select the best one for my case Smile

I filed an enhancement request for having the easy to use @Formula feature in EclipseLink as well:
https://bugs.eclipse.org/bugs/show_bug.cgi?id=296324

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