How does FetchType.LAZY affects Entities called by a client?

[heinrich]

Hi,

i'm wondering how the fetchtype LAZY affects Entities which are requested by a client through an SessionBean.
I build some samples to figure out how this works.
All my Entities are marked with fetch=FetchType.LAZY. There are some n2m, one2m relations.
I wrtoe a SessionBean which requests an entity and requests the related entities from the n2m relations.
The logfiles from my PostgresSQL told me, that there is a SQL Query to get the root entity and when the session bean runs the second call, the dependent entities are requested from the database. Fine, thats how i expected this.

My question:
I got an client, calling a method on the session been which returns a reference to the entity bean. On this entity im calling the same operations as the SessionBean has done befor in the container.
The database log shows only one initial query for the whole relation tree.
So, does the FetchType.LAZY affects the entities used by clients?
I guess not.

[martinganserer]

Hello Heinrich,

I already had a similar question. Please got to:
http://www.jboss.com/index.html?module=bb&op=viewtopic&t=69112

Maybe it helps you further!

[heinrich]

hi,

thanks a lot.
It does not satisfy my intention. I thought the ValueObjects were obsolete in EJB3.0.
So i have to rebuild my application for speedup.

bye

[martinganserer]

Hi,

wait a moment! You don't need Value Objects necessarily when you work with lazy loading in a thin client environment. But as soon as you jump over the border of the remote interface you have to take an alternative approach. Do you have a fat client - swing for example?

[heinrich]

hmm, yes i have. Its a Swing Client. It was written for EJB2.1 and we now have to go further on the project and migrate it to ejb3.0.
All teh entities, interfaces, value and lightValue object were generated by middlegen. But the middlgen plugin for ejb3.0 is not that capable for these features.
So we have to implement them on our own like some other improvements for ejb3.0.
Thanks for your help

martin

[silviu.marcu]

http://docs.jboss.org/ejb3/app-server/tutorial/merge/merge.html

contains an explanation of detached objects (value objects)

You need only to define what data to be contained into the detached objects (for lazy relations you can create extra methods with queries to populate only the relations needed, this gives you flexibility to choose what to send outside the ejb container)

see the JOIN FETCH option into the ejb3 documentation

[heinrich]

Thanks,
that's how a expected it to work.
But the case using the lightValueObject isn't defined anywhere i guess.