Hey guys I have the following Object graph

Under what conditions would an object in a list not initialize and throw the follwoing

2005-12-12 16:45:31,204 [http-8080-Processor23] ERROR org.hibernate.LazyInitializationException.<init>: 19 - could not initialize proxy - the owning Session was closed
org.hibernate.LazyInitializationException: could not initialize proxy - the owning Session was closed

I do the following :
0. I have a detached Object
1. Open a new hibernate session
2. reatach the detached object with the session by doing this

s.refresh( object );
s.lock( object, LockMode.NONE );
3. and then try to navigate the graph to get to an object in a list

So session is open the main object is in the session and yet i cannot
get to some areas in the object graph ??

Any thoughts ?

Makw sure this stuff is thread safe.

THank you for the response.

I think i am already doing that . I use the thread local to store my session
the way that is implemeted is pretty much the same way as described in Hibernate in Action book page 301 .

I do use a Filter too , My application uses struts + hibernate and deployed
under tomcat 5.5.12 Java 5.


protected static ThreadLocal sessionHolder = new ThreadLocal();
....
public static Session getCurrentDBSession() throws ScapeException
{
Session sess = (Session) sessionHolder.get();
try
{
if ( sess == null )
{
sess = getSessionFactory().openSession();
sessionHolder.set( sess );
}
}
catch ( HibernateException e )
{
}
return sess;
}

public static SessionFactory getSessionFactory()
{
ApplicationProperties props = ApplicationProperties.getInstance();
SessionFactory factory =
(SessionFactory) props.getApplicationProperty( HIBERNATE_FACTORY );
return factory;
}

Yes, it must be thread safe. It looks like you are misusing "refesh"



Try to relaod object by ID (implement some interface for all persistent classes to obtain it), it must work without problems.

BTW I do not see how you detache objects, if you store it in httpsession then you must serialize access to httpsession anyway (it happens if user refreshes page before to recieve response)

Thank you baliukas for your responses .

BTW I do not see how you detache objects, if you store it in httpsession then you must serialize access to httpsession anyway (it happens if user refreshes page before to recieve response)

I use the Filter mechanism So everytime the response is returned i close the session. So now i have a detached object and yes i do store the object in the Http Session.
then if in the next request response loop i need to use the object i call on it
s.refresh( object );
s.lock( object, LockMode.NONE );

where i know that the object hasn't changed so i refresh it and then just put it in the session. So yes i will try removing the call to refresh and see what happens

I do not undrestand what u mean by you must serialize access to httpsession ?


try to relaod object by ID (implement some interface for all persistent classes to obtain it), it must work without problems.

Do you mean use Session.load(Class theClass, Serializable id)
instead of
s.refresh( object );
s.lock( object, LockMode.NONE );


Again thanks for the help

Yes, just try to remove "s.refresh( object ); " first as I understand documentation it is not designed for detached instances and it does not cascade.
Next problem is persistent objects in http session, it must throw "Illegal attemt to associate object with two open sessions" (two concurrent threads attemt to attach object ) Workaround is to use some session scope attribute to detect concurrent session access serialization/synchronization is application specific, but application designed this way is a DOS attack victim anyway.

Thank you Baliukas for your suggestions .

But doing only this
session.lock( object, LockMode.NONE );

resulted in the following exception
org.hibernate.HibernateException: reassociated object has dirty collection reference (or an array)

Although the object which is stored in a POJO is not being modified. We do the following

-open session
- execute the query to get the objects
- object loads with couple lists lazilly initialized
- We display some of these lists on jsp.
-close session

-open session
-try to initialize a single object with the new session
session.lock( object, LockMode.NONE );
and hence the exception.

It seems that i am doing something awfully wrong here cause this shouldn't be this tough

Reading the Session.lock(Object object,LockMode lockMode)
simply reassociate a transient instance with a session (LockMode.NONE)

Now according to my undrestanding
- Transient Object : means the object isn't associated with any database table row; object was instantiated using the new operator.

- Persistent Object : a persistance instance is an instance with a database identity; persistent instances are always associated with a Session and are transactional

-Detached Object : Is a persistant instance that has lost association with the persistence manager( session)

Now the above said the lock definition doesn't seem to make sense when we are talking about detached objects is that true ?

THank you again

It must be better to store object id in http session (or url parameter if possible), "Detached Object " doe's not make sence if you need to refresh before to attach. It must help to avoid many problems.

Well the following seems to have solved my problem

instead of calling
session.refresh(object);
session.lock(object, lockmode.NONE) ;

on the object which was resulting in exceptions I call

so = (ScapeObject)s.merge(object);
and use the new object as my persistant object and get rid of
the old one.

Well i guess my open question would be why doesn't

session.lock(object, lockmode.NONE); work


Thank you for the help

It is a legimate question indeed.
And according to API docs:


As you can see doc's state that operation cascades to associated instances, but I can't find how to map association with cascade="lock" ...

I belive that it is a bug that lock() does not associate object tree with given session.

Revisiting this ,

Well as you point out the definition in the api. I think you are not supposed to use this method to associate a detached object with the session.

they say
simply reassociate a transient instance with a session
and according to the documentation there is a big difference betweeen a
detached object and a transient object.

What i do now with the detached objects is the following,
0. session opens
1. A query gets me a list of objects
2. session closes
3. i choose the object i want to use
4. open session 2
5. and call Session.get on that object to reload its state
6....