> You'll need to also listen to PostUpdate and may be PostRemove.
Yes definitely. Thank you. I hadn't quite thought it all the way through.
> Why do you think that they are not part of the transaction?
I don't really have an understanding of how the transactions are
working yet. I guess I'll have to do some research :) Would a call to
a web service be rolled back if there is an error?
Thank you so much for your help.
On 8/3/07, Marina Vatkina <Marina.Vatkina_at_sun.com> wrote:
> Kem,
>
> Kem Elbrader wrote:
> > Sorry I'm not sure all of code I tried to send before made it and I
> > don't think my explanation was very clear. Here's a second attempt. :)
> >
> > I have an entity that is represented in a third parties database and
> > the only access I have to it is through a web service. I can't change
> > the third parties schema. I need to add some data (properties) to the
> > entity and would like to use JPA to do so. I'm considering using the
> > PostLoad and PostPersist annotation to populate and save/update the
> > data in the third party database to the entity which I create using
> > JPA.
>
> You'll need to also listen to PostUpdate and may be PostRemove.
>
> >
> > Below is a modified version of what I sent originally (hopefully it's
> > a little easier to understand). Do you think that the solution below
> > is a good idea? I've realized a couple of possible issues. As far as I
> > know this method won't participate in the transaction that JPA uses
> > and couldn't roll back changes in case of an error.
>
> Why do you think that they are not part of the transaction?
>
> Also there is
> > nothing to guarantee referential integrity... but I think that's more
> > of a problem with relating data in two different DBMSs.
>
> You can use 2 PUs with 2 EMs and a single facade that hides from the user the
> fact that they are working with 2 completely different entities.
>
> thanks,
> -marina
>
> >
> > @Entity class User {
> >
> > @Id String id;
> > @Transient int externalId; // acts as a "foreign key" into the third
> > party's db
> > @Transient String name; // existing data
> > int newData; // new data
> >
> > @Transient WebServicePort port;
> >
> > User() {
> > WebService service = new WebService();
> > port = service.getWebServicePort();
> > }
> >
> > // getters/setters for properties
> >
> > @PostLoad void initializeUser() {
> > Rep rep = port.findRep(externalId); // get needed data from ws
> > this.setName(rep.getName()); // copy data to transient field
> > }
> >
> > @PostPersist void saveUser() {
> > Rep rep = new Rep();
> > rep.setId(externalId);
> > rep.setName(name);
> > port.persist(rep); // saves or updates using ws
> > }
> > }
> >
> > On 8/1/07, Marina Vatkina <Marina.Vatkina_at_sun.com> wrote:
> >
> >>I'm not sure that I understand it correctly. If you don't want to map a field to
> >>a column in a database, you do mark it as @Transient. But do you plan to
> >>override it in orm.xml later on? If not, what's the purpose of such field?
> >>
> >>thanks,
> >>-marina
> >>
> >>Kem Elbrader wrote:
> >>
> >>>I understand that @Transient "means" don't populate and don't write
> >>>but I need a way to keep JPA from populating the field since it
> >>>doesn't even exist in the database that JPA is using.
> >>>Would updateable=false do this? Is there another way to mark a field
> >>>as not being used by JPA that doesn't "mean" that it won't be
> >>>persisted somewhere?
> >>>
> >>>On 7/31/07, Marina Vatkina <Marina.Vatkina_at_sun.com> wrote:
> >>>
> >>>
> >>>>Kem,
> >>>>
> >>>>You should be able to mark the existing fields as 'updateable=false' but
> >>>>@Transient means not only to skip during write to the database, but also never
> >>>>populate during the read.
> >>>>
> >>>>Regards,
> >>>>-marina
> >>>>
> >>>>Kem Elbrader wrote:
> >>>>
> >>>>
> >>>>>Here's the situation.
> >>>>>
> >>>>>A company uses a database that stores information about its customers.
> >>>>>A web interface is available for customer service representatives to
> >>>>>update the customers name, phone number, etc. The web interface is not
> >>>>>suitable for customers to use so the company has a calling center that
> >>>>>enables the customers to request changes. The database and web
> >>>>>interface were produced by a third party which is unwilling to make
> >>>>>changes to the existing system. The third party does provide a web
> >>>>>service with operations to create, update, and delete the data.
> >>>>>
> >>>>>The company wants to provide a web interface to allow customers to
> >>>>>update their information themselves. Further, the company wants to
> >>>>>produce additional services which will require extra data that is not
> >>>>>stored in the original database. For example, some of the entities
> >>>>>represented in the original database simply need some properties added
> >>>>>to them. It's not viable to reproduce the existing system. So a new
> >>>>>system must be created that is capable of updating the data in the
> >>>>>existing system, persist the new data and provide the new
> >>>>>functionality.
> >>>>>
> >>>>>I was hoping I could use JPA to model the new and old data together so
> >>>>>that a single object could be used in the cases where simple
> >>>>>properties need to be added to the existing entities. Is this
> >>>>>reasonable?
> >>>>>
> >>>>>Here is my current approach.
> >>>>>
> >>>>>@Entity
> >>>>>@EntityListeners({UserListener.class})
> >>>>>class ExampleUser {
> >>>>> @Id String login; // new data
> >>>>> @Transient String name; // existing data
> >>>>>
> >>>>> String getLogin() { return login; }
> >>>>> void setLogin(String login) { this.login= login; }
> >>>>>
> >>>>> String getName() { return name; }
> >>>>> void setName(String name) { this.name = name; }
> >>>>>}
> >>>>>
> >>>>>class UserListener {
> >>>>> @PostLoad void initializeUser(Object entity) {
> >>>>> // use web service to obtain the users name
> >>>>> // copy the name to ExampleUser.name
> >>>>> }
> >>>>> @PostPersist void saveUser(Object entity) {
> >>>>> // use web service to save ExampleUser.name
> >>>>> }
> >>>>>}
> >>>>>
> >>>>>I believe this is similar to your suggestion but I'm not quite sure
> >>>>>what you meant. Can you clarify your suggestion?
> >>>>>
> >>>>>On 7/30/07, Craig L Russell <Craig.Russell_at_sun.com> wrote:
> >>>>>
> >>>>>
> >>>>>
> >>>>>>Hi Kem,
> >>>>>>
> >>>>>>Can you model this as an EJB that is created by other EJBs and that
> >>>>>>contacts the third party web service plus the Entity?
> >>>>>>
> >>>>>>Craig
> >>>>>>
> >>>>>>On Jul 30, 2007, at 11:47 AM, Kem Elbrader wrote:
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>>I have an entity which has a few properties that aren't persisted to
> >>>>>>>the database but rather obtained from a third party web service. How
> >>>>>>>would you suggest going about accomplishing this?
> >>>>>>>
> >>>>>>>On 7/30/07, Craig L Russell <Craig.Russell_at_sun.com> wrote:
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>>Hi Kem,
> >>>>>>>>
> >>>>>>>>I'd suggest you rework your design such that you only use references
> >>>>>>>>"from" EJBs "to" Entities and other EJBs.
> >>>>>>>>
> >>>>>>>>Having Entities reference EJBs violates the basic POJO model.
> >>>>>>>>
> >>>>>>>>Regards,
> >>>>>>>>
> >>>>>>>>Craig
> >>>>>>>>
> >>>>>>>>On Jul 30, 2007, at 11:22 AM, Kem Elbrader wrote:
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>Is it possible to inject an EJB into an Entity? If not is there
> >>>>>>>>>another way to get a reference to a EJB from an Entity?
> >>>>>>>>>
> >>>>>>>>>Example:
> >>>>>>>>>
> >>>>>>>>>@Entity
> >>>>>>>>>public class Customer {
> >>>>>>>>>
> >>>>>>>>> @EJB
> >>>>>>>>> CustomerAction customerAction;
> >>>>>>>>>
> >>>>>>>>> @PostLoad
> >>>>>>>>> void initialize() {
> >>>>>>>>> // do stuff with customerAction...
> >>>>>>>>> }
> >>>>>>>>>}
> >>>>>>>>
> >>>>>>>>Craig Russell
> >>>>>>>>Architect, Sun Java Enterprise System http://java.sun.com/products/
> >>>>>>>>jdo
> >>>>>>>>408 276-5638 mailto:Craig.Russell_at_sun.com
> >>>>>>>>P.S. A good JDO? O, Gasp!
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>
> >>>>>>Craig Russell
> >>>>>>Architect, Sun Java Enterprise System http://java.sun.com/products/jdo
> >>>>>>408 276-5638 mailto:Craig.Russell_at_sun.com
> >>>>>>P.S. A good JDO? O, Gasp!
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>
>