np. I think it's a good question you have there. You could make your model load method check if it were called via submit or not, you might do this via an hidden field and the updating it when the user clicks the submit button. Im not sure when wicket loads the values, im guessing after the submit has been processed right?
Although this does not feel like the wicket way approach. Dimitrio wrote: > Hello, Nino. > > Thanks for a quick reply! > > I think clearing the Hibernate session cache (via Session.clear()) > before saving the city will work for me in this case. > > However the second concern remains. Consider a complex form with tens > of drop down choice or list components. I want them loaded once > (during the rendering phase) or reloaded upon page refresh (when the > user refreshes a page, they expect to see fresh reference data). > During submit I would try to avoid sucking in all that data from the > database again. > > I wonder if there is a solution to that or maybe some "Wicket design > pattern" to approach such situations. > > Best regards, > Dimitrio > > On 5/9/07, * Nino Saturnino Martinez Vazquez Wael* > <[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>> wrote: > > Hi Dimitrio > > The solution(possibly) to your first problem are to call flush on your > hibernate session. Altthough im far from a hibernate expert, this > solved > our problems with that kind of exception. You could also try > merge(), im > afraid im just guessing at this point. > > regards Nino > > Dimitrio wrote: > > > > Hello All, > > > > I am evaluating the possibility to use the Wicket / Spring / > Hibernate > > stack for my next project (Spring / Hibernate being used for the > > middle tier + OpenSessionInViewFilter). > > > > Let me describe a simple test scenario that I am trying to > implement - > > a City Editor panel. The panel contains a text field with a city > name > > and a drop down choice with the available countries. > > > > The domain model (mapped to the DB via Hibernate) is the following: > > > > City > > --------- > > Long id; > > String name; > > > > @Cascade(SAVE_UPDATE) > > Country country; > > > > Country > > ------------ > > Long id; > > String isoCode; > > String name; > > > > Upon construction, the Country drop down choice for the panel is > > provided with a LoadableDetachableModel that loads a list of all > > available countries from a CountryDao. The form itself has a > > CompoundPropertyModel for the city being edited. > > > > The page renders just fine, the country list is correctly reloaded > > upon F5 - everything as expected. > > > > However, when the user clicks Submit, the form component reloads the > > country list again (so the list ends up in the new Hibernate session > > cache) and when I try to save the city in onSubmit, I sometimes > get a > > Hibernate exception with the following message: > > > > a different object with the same identifier value was already > > associated with the session: [test.wicket.Country#6]; nested > exception > > is org.hibernate.NonUniqueObjectException: a different object > with the > > same identifier value was already associated with the session: > > [test.wicket.Country#6] > > > > This exception only occurs if the user does not change the city's > > country. In that case the Country instance referenced by the city is > > different from the corresponding instance in Hibernate session cache > > and the SAVE_UPDATE cascading fails. > > > > So, my first question is whether there is a way to avoid this > exception? > > > > The second thing is that I do not generally want all my > reference data > > being completely reloaded on every submit. > > > > I really liked the way property editors were used in Spring to > > retrieve and validate reference data for such scenarios. In Spring I > > would have a CountryPropertyEditor that would retrieve the Country > > instance by an ISO code or ID and assign it to the city. > > > > So in Spring the submit would result in 2 statements like below: > > > > select from country where id=... > > update city where id=... > > > > and avoid the duplicate instances problem altogether. > > > > So, the second question is whether there is a way to not reload all > > the reference data upon submit? How do you address such scenarios in > > your Wicket applications? > > > > > > Many thanks! > > > > --Dimitrio > > > > > > > ------------------------------------------------------------------------ > > > > > ------------------------------------------------------------------------- > > This SF.net email is sponsored by DB2 Express > > Download DB2 Express C - the FREE version of DB2 express and take > > control of your XML. No limits. Just data. 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