Re: Mapping POJOs

From: Marc Hadley <Marc.Hadley_at_Sun.COM>
Date: Fri, 13 Apr 2007 09:25:30 -0400

On Apr 12, 2007, at 8:03 PM, Dhanji R. Prasanna wrote:
> > When you write POJO do you mean the application data object ? As a
> > counter example, we've been working on an example that uses
> > JPA where
> > the application data objects are in the form of JPA entites. The
> > classes that contain our annotations are separate and are
> > much closer
> > to controllers in the MVC sense.
> This sounds like a perverted use of JPA. The POJO objects that are
> your "model" are intended to be annotated with javax.persistence
> annotations so that they can directly be mapped to the RDMBS layer.
> This is certainly how hibernate and toplink work. I am not aware
> that JPA has altered that philosophy in any way.
I think you might have missunderstood, our model objects *are*
annotated with JPA annotations. E.g.:

public class Widget {

public class WidgetResource {

   XmlWidget getWidget(@UriParam("widgetid}) String id) {
      Widget w = ...
      return new XmlWidget(w);

Widget is a model class using JPA, WidgetResource is a controller (a
resource) and XmlWidget is a wrapper class that is annotated with
JAXB annotations to define an XML "view" (a representation) of a Widget.

> IMHO, the MVC paradigm is different (with some similarities) to the
> paradigm. Instead of speaking of Controller and View, we should be
> speaking
> in terms of Resource and Representation.
> This is a reasonable analog. The model of course plays the same
> role in both ( i.e. entity).


Marc Hadley <marc.hadley at>
CTO Office, Sun Microsystems.