Is there a good example of using lazy loading in a web app somewhere?

Essentially what I want to do is (using an example with single User has multiple contacts): find a User object without loading the contacts collection and put it into the HttpSession. Then later (in another request) get the User object from the HttpSession and get the contacts for the User.
It sounds simple however all my attempts so far have resulted in a Could not lazily load collection - no session.

Thanks,
Jerry.

use session.lock(user, LockMode.NONE) in the second request

I tried your suggestion in my code, but I still get the same error. First I am trying to lazily load the contacts in the same request. In the struts action class I get a single User and then try to get the contacts for that user in another call to the DBService class.

The second call has the session.lock(user, LockMode.NONE) code in it.

Jerry.



List userList = DBService.getInstance().getUserList();

User user = (User)userList.get(0);

Set contacts = DBService.getInstance().getUserContacts(user);




public class DBService
{

private static DBService instance = null;

private DBService()
{

}


public static synchronized DBService getInstance()
{
if (instance == null)
{
instance = new DBService();
}
return instance;
}


public List getUserList()
{
Session session = ConnectionFactory.getInstance().getSession();

try
{
Query query =
session.createQuery(
"select user from User user");

System.out.println("size is: " + query.list().size());

return query.list();

}
catch (HibernateException e)
{
System.err.println("Hibernate Exception" + e.getMessage());
throw new RuntimeException(e);
}
finally
{
if (session != null)
{
try
{
session.close();
}
catch (HibernateException e)
{
System.err.println("Hibernate Exception" + e.getMessage());
throw new RuntimeException(e);
}

}
}
}


public Set getUserContacts(User user)
{
Session session = ConnectionFactory.getInstance().getSession();

try
{
session.lock(user, LockMode.NONE);
return user.getContacts();

}
catch (Exception e)
{

throw new RuntimeException(e);
}

finally
{
if (session != null)
{
try
{
session.close();
}
catch (HibernateException e)
{
System.err.println("Hibernate Exception" + e.getMessage());
throw new RuntimeException(e);
}

}
}
}

}

Are you using a recent hibernate version?

Yes I am using the latest version of Hibernate.

I am pretty sure reassociating works with recent Hibernate, I am using this myself all the time. You must be missing something.

Would you have a code sample I can take a look at?

Thanks,
Jerry. (jerry_s220@yahoo.com)

I am pretty sure your code should work, mine looks very similar, I even pass the objects around to a remote app-server before reattatching. Is what you have shown really exactly the stuff you do?

I think I have it working now. After I added this extra line after session.lock(user, LockMode.NONE) it seems to work fine:

Hibernate.initialize(user.getContacts());

I hope this will be useful for the other users to know..

Jerry.