Kem,
Kem Elbrader wrote:
>>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?
I tried to find an easy answer to this question, but it seems to depend on where
your webservices are located. I suggest to send this question to the users alias
to get help from a broader audience.
Regards,
-marina
>
> 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!
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>