Are there any solutions to the problem explained in: http://brian.pontarelli.com/2006/04/26/ ... -fetching/

Briefly:

Hibernate doesn’t fetch collections within a bean in the same session the beans were created in. If you need objects in those collections later on within that session, you had better put them in there. This even holds true when you go back to hibernate to refetch the same object instance. Here’s a quick example:

User user = new User("Brian", "Pontarelli");
userDAO.saveOrUpdate(user);

Role role = new Role();
role.setUser(user);
roleDAO.saveOrUpdate(role);

user = userDAO.fetch("Brian", "Pontarelli");
user.getRoles().get(0); // THIS IS NULL!

Once the session is closed out and the fetch is performed in a new session then this will work fine. I can see how this behavior protects the object instance somewhat, but this means that the instance also misses any updates within other threads to its associations.

--
gurkan

Wow...did you read the documentation????
This is actualy normal hibernate behaviour....
If an object contains a collection and you want hibernate
to get that collection immediatly you have to spcify that in some way
lazy="false" in your mapping documents ....
or in HQL inner join fetch..... or in your Criteria setFetchMode("",FetchMode.JOIN)......

This is not the problem of lazy evaluation.

There is one-to-many relation between user and roles. In user there is a persistent collection roles with cascade save-update.

User user = new User("Brian", "Pontarelli");
userDAO.save(user);

I can add roles to user like below:

Role role = new Role();
role.setUser(user); // has also inverse relation defined
user.getRoles().add(role);
userDAO.update(user); // since cascade

and get the role like below:

user = userDAO.fetch("Brian", "Pontarelli");
user.getRoles().get(0); // THIS IS NOT NULL!

--------------------------------------------------------------

However if I try to save role explicitly as below:

User user = new User("Brian", "Pontarelli");
userDAO.save(user);

Role role = new Role();
role.setUser(user); // has also inverse relation defined
roleDAO.save(role);

I am willing to see this change in the collection of the newly fetched user.

user = userDAO.fetch("Brian", "Pontarelli");
user.getRoles().get(0); // THIS IS NULL!

After flushing sessions i can see the same changes on the databases. The problem is that fetching collection is not aware of the objects in the session cache.

--
gürkan

I don't see a problem with the scenario you describe. It seems to be behaving as it should. In the case where user.getRoles().get(0) returns null, you never added the role to the user explicitly. In the case where it is not null, user.getRoles().add(role), then userDAO.update(user) you are explicitly adding the role to the user and updating it's persistent state. I don't see what the alleged "bug" is. It looks like it's working as intended.

Do u get the value when you refresh the session after saving the role!!!!!!

If the session is flushed, I can get the correct result.

User user = new User("Brian", "Pontarelli");
userDAO.save(user);

Role role = new Role();
role.setUser(user); // has also inverse relation defined
roleDAO.save(role);

session.flush();

user = userDAO.fetch("Brian", "Pontarelli");
user.getRoles().get(0); // THIS IS NOT NULL!


I will try it again with inverse relation have cascade definition. But at my first try results didn't change. Maybe I did something wrong. I will try it again.

--
gurkan