Hello everyone.

I'm using Hibernate 3.2.6.GA with Hibernate-EntityManager 3.3.1.GA and Hibernate-C3P0 3.3.1.GA (maven deps). Hibernate is hooked up through Spring 2.5. All of my persistent objects are written in JPA with the DAOs written with Spring JPA. The database behind all of this is MySQL 5 and i'm using C3P0 to manage the connection pool.

Here's my scenario. I have two classes; let's call them Model and Brand. I create a new Brand object and persist it to the database. I then create a new Model object and assign the recently persisted Brand object as part of its member variable. In the Model class Brand is linked using the following annotations.



Now when I try to persist the Model object I get the following error from Hibernate.



Each call to persist occurs within its own transaction as the Dao classes are written as @Transactional. Can anyone explain why this is happening? This is a pretty big problem for me if I can't link classes together.

Thanks in advance

You use @OneToOne(cascade = CascadeType.ALL), so you tell hibernate to also persist the brand, when persisting a model. You can either disable cascading or use merge(brand) before persisting your model.

Ok. I tried using merge(brand) before the persist(model) and it doesn't seem to have made any effect.

I'm fairly new to the whole hibernate/jpa setup. I was expecting that hibernate would realize the brand was already in the database and just wouldn't do anything. Only if the brand was clearly not in the db would it get persisted. I was under the impression you get all of this for free (after all isn't that the point of a persistence tech, to take care of tedious book keeping). Maybe i'm expecting too much from hibernate.

Is there an annotation I can give the brand member variable in model that will effectively do what I want?

You don't need to call persist. Do one of the following:

Add (unpersisted) brand to model and merge model. Since your CascadeType is set to all, it will insert both.

Or...use the brand RETURNED from merge to add to model. Then persist on model should work.

Merge will help w/ DetachedEntity issues because it will figure out from the ID whether to update or insert

Adding an unpersisted model and brand works no problem.

The issue here is that hibernate is behind a web service and the web service interacts with clients. So a common situation is a client wishes to create a new model. The client pulls the brand from the web service, adds it to the new model object and then attempts to push the new model to the web service. Then the web service attempts to add the model to the database and since the brand is already inserted we get an error. I can perform merges or pull the data again before I attempt to insert the model but I was hoping to avoid having Dao's rely on other Dao's. Maybe that is the only way though.