On Fri, Jun 5, 2009 at 3:12 PM, Daryl Stultz <da...@6degrees.com> wrote:
> On Fri, Jun 5, 2009 at 3:51 PM, Michael Dick <michael.d.d...@gmail.com
> >wrote:
>
> > Maybe I'm misunderstanding the use case, but the real coupling is the
> named
> > queries to persistence.xml (persistence unit) - not necessarily the
> > compilable unit.
>
>
> This is the case for me. In my pre-JPA world I have a Widget model class
> and
> a WidgetUtils class which manipulates Widgets, call WidgetUtils "business
> logic". I might define WidgetUtils.sharpenDullWidgets() and in that method
> I
> have
>
> String query "select * from Widgets where Widgets.dull = 1";
> ... get connection, run query, traverse resultset...
>
> I don't like embedding SQL in my Java, but I do like have the business
> logic
> contained in the query right in the business method sharpenDullWidgets. So
> really, my proposal doesn't get me what I want. Putting named queries in a
> super class, a registry class or an xml file helps in that it gets the
> queries out of the model but it doesn't put it in the business logic class.
>
> Really, I think the best I could hope for is to be able to define named
> queries as annotations of the method that uses it even if the method is in
> a
> non-entity class:
>
> public class WidgetUtils {
>
> @NamedQueries( {
> @NamedQuery(name="findDullWidgets",
> query="select...")
> })
> public static void sharpenDullWidgets() {
> Query query = em.createNamedQuery("findDullWidgets");
> }
>
> The query is much closer to the point of usage. I don't think anybody would
> be interested in making the above work. Of course I could write the query
> on
> the spot and the only thing I lose is the performance of the pre-compiled
> query.
>
I think the query isn't compiled until the first time you use it and then
it's cached by its string form. Might have to look at that code again to
verify though.
If that's the case then I think I'd just use a static string instead of a
NamedQuery.
public class WidgetUtils {
private static final String qFindDullWidgets = "select . . .";
public static void sharpenDullWidgets() {
Query query = em.createQuery(qFindDullWidgets);
}
}
I don't think there's a significant performance difference between the two
(if the annotation worked). The annotations might be more expressive
though..
In order to make the annotations work automagically we (JPA provider) would
have to scan the classpath for non entity/msc types that have @NamedQuery
annotations.. If exclude-unlisted-classes == false this might not be much
additional overhead.
You're welcome to open a JIRA for this as an improvement if it'd be a big
help to you. I can't promise a target date though.
-mike
>
> --
> Daryl Stultz
> _____________________________________
> 6 Degrees Software and Consulting, Inc.
> http://www.6degrees.com
> mailto:da...@6degrees.com
>
