Why exception coming on accessing collection

[Gaurav Verme]

Hi,

I was going through the hibernate docs and came through the below code

s = sessions.openSession();
Transaction tx = s.beginTransaction();
            
User u = (User) s.createQuery("from User u where u.name=:userName")
    .setString("userName", userName).uniqueResult();
Map permissions = u.getPermissions();

tx.commit();
s.close();

Integer accessLevel = (Integer) permissions.get("accounts");  // Error!

Can you please explain that why its giving error at line 11 even if we have called the getPermissions() method on the retrieved object.

[Paul Sturrock]

Without knowing what error is being thrown all we can do is guess.

[Gaurav Verme]

Since the permissions collection was not initialized when the Session was closed, the collection will not be able to load its state. Hibernate does not support lazy initialization for detached objects.

[Gaurav Verme]

Hi,

Any pointers why the above code will give exception

[Paul Sturrock]

There is no open session when you access your collection. The collection has not been initialized because (presumably) it is configured for lazy initialization (?) and there is no mechanism not to initialize it.

[Gaurav Verme]

Thanks for replying.

One thing need to confirm that once we are doing

Map permissions = u.getPermissions(); 

then will it not fetch the collection from DB because we are calling the getter method on the same

[Paul Sturrock]

Without seeing how you've mapped this I can't say, but I'll guess your collection related to an association in the database? In which case Hibernate will try to load this if it is not already loaded. And it will fail if there is no open Session to use.

[Gaurav Verme]

This is from hibernate documentation:

http://docs.jboss.org/hibernate/core/3.3/reference/en/html/performance.html#performance-cache

[Paul Sturrock]

Indeed it is. How is it related to your question? Are you using the second level cache? If you are then you understand that something has to put object into this cache in the first place, and nothing in your code does that.