Good links for architecture

passionlessDrone · **Joined:** Fri Jun 03, 2005 11:36 am **Posts:** 8

Hello friends -

I think I've got the basic O/R mapping deal down. What I seem to be lacking is the vision to put together an architecture to integrate Hibernate in and do things that way (I think) they should be done.

For example, I've got a parent child relationship I'd like to populate every time I grab the parent; and have those children be available to push into the session. I'd like to have Hibernate populate my set of children objects automatically. Finally, I'd like to have a simple DAO that allows calls from other layers that don't require other layers to understand Hibernate sessions, or anything else about persistence. These other layers could expect to get a series of fully populated objects back.

I feel like I must be missing something by coming to the consusion that this is impossible to handle in Hibernate; unless I were to develop a solution so unweidly, it would be easier to manage by just going ahead and writing the necessary getChildrenByParentId() methods everywhere and being done with it.

I feel like I'm at the point where I can brute force something together but get the feeling if I could see the big picture I would wind up with something much better.

Any advice is greatly appreciated.

- pD

oharsta · **Joined:** Wed Oct 06, 2004 2:49 am **Posts:** 12

Christian has written an excellent blog regarding this topic:

http://blog.hibernate.org/cgi-bin/blosx ... 2005/09/08

pepelnm · **Posted:** Sun Jun 04, 2006 5:16 am

You need eager fetching.

You can try something like these in mapping files:

Code:

<set name="permissions" 
            fetch="join">
    <key column="userId"/>
    <one-to-many class="Permission"/>
</set>

or

Code:

<many-to-one name="mother" class="Cat" fetch="join"/>

Or you can try something like this in HQL queries:

Code:

select 
   p
from 
   Person p 
   left join fetch p.events 
where 
   p.id = :pid

read 19.1. Fetching strategies chapter in Hibernate reference

passionlessDrone · **Joined:** Fri Jun 03, 2005 11:36 am **Posts:** 8

These are great examples, very helpful.

Thank you all.

- pD