Re: How to use the LoadableDetachableModel in a Wicket, Spring, Hibernate based web application correctly?

[jcgarciam <jc...@gmail.com>]

To avoid having detached objects in your web layer, try wrapping wicket
filter with the Spring OpenSessionInView
<http://static.springsource.org/spring/docs/2.5.x/api/org/springframework/orm/hibernate3/support/OpenSessionInViewFilter.html>filter,
in that way transaction will be bound to the -> HttpRequest -> HttpResponse
cycle, or you can you use a more wicket way and override onBeginRequest /
onEndRequest to do your transaction work there.


On Fri, Aug 12, 2011 at 5:52 AM, Florian B. [via Apache Wicket] <
ml-node+3738252-887758337-65838@n4.nabble.com> wrote:

> I'm developing a web application based on Hibernate, Spring and Wicket.
>
> Until now I implemented the business objects and the persistence layer. The
> transaction is managed by a transaction interceptor of the Spring framework
> and the HibernateTransactionManager. So each method of the DAO classes is
> encapsulated in a transaction. Implementing this together with unit test was
> straight forward.
>
> Now I come to the web application part where I also use Spring for
> dependency injection. Together with the @SpringBean annotations of the
> Wicket framework I inject the DAOs in the Wicket components. But as I'm
> pretty new to Wicket I'm a little bit stuck when using the right model for
> my business objects when passing them do the Wicket components. The problem
> is that I got a lot of exceptions due to detached business objects, which
> are not connected to the Hibernate session any more.
>
> I tried to use the LoadableDetachableModel solve the issues. I put the
> business object into a LoadableDetachableModel which I put into a
> CompoundModel which then is bound to Form. The form is on a page which
> should be used to create new business objects and also to edit exiting ones
> depending on the input parameters of the page.
>
> If there is a id in the parameters then the corresponding business object
> should be loaded from the database. When there are no parameters then a new
> business object should be created. The part were a object should be edited
> runs quite well but when a new object should be created, and I fill out the
> web form and press save, I get a NullPointerException. After some debugging
> I found out that LoadableDetachableModel could not return an instance of the
> business object as the overridden load() method could not load the object
> form the database as it was not saved there yet and therefore has no id.
>
> So now I'm wondering how to solve this problem. Is the
> LoadableDetachableModel the right choice? Is it advisable to separate the
> form into two interdependent forms and each form uses a different model. So
> only the edit page/form uses the LoadableDetachableModel?
>
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-- 

JC


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