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Re: [eclipselink-users] Calculating progress for an entity based on data from another table
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You can define a relationship in EclipseLink based on any EclipseLink
Expression. There is currently no JPA annotations for this, but you can use
a DescriptorCustomizer to add the mapping using the mapping API and setting
a selectionCriteria on the mapping.
Other options within JPA would be to query for the results instead of
mapping them.
See,
http://en.wikibooks.org/wiki/Java_Persistence/Relationships#Filtering.2C_Complex_Joins
philk wrote:
>
> Hello,
>
> I am working with a legacy database where the warehouse order progress is
> calculated depending on many line items are finished. So I have 2
> Entities:
>
> WarehouseOrder
> LineItem
>
> the orders progress is calculated using the number of LineItems that have
> their state field set to anything but 1.
>
> I would have a transient field in WarehouseOrder that holds the progress.
> I checked the @PostLoad listeners, but they have no session context so I
> can not execute any query. In Hibernate there is the @Formula annotation
> that allows you to specify a query for filling in the annotated field.
>
> I tried this:
>
> @SqlResultSetMapping(name = "progress", columns = @ColumnResult(name =
> "progress"))
> @NamedNativeQuery(name = "progress", query = "select 100 * (select
> count(p) from LegacyOrderPosition p, LegacyPickOrder o where p.id=o.id and
> p.status!=1) / count(p) as progress", resultSetMapping = "scalar")
>
> But to no avail. Of course I got it wrong somehow, I know :)
>
>
> Any ideas how this could be solved in EL? Maybe using an embedded Entity?
>
> Thanks for any input,
> Phil
>
-----
http://wiki.eclipse.org/User:James.sutherland.oracle.com James Sutherland
http://www.eclipse.org/eclipselink/
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