Hi, i've a problem with realize ternary relation...
I use a very simple example for explain my problem:
DB is composed of four table:
- users (userId,name)
- groups (groupId,description)
- role (roleId,description)
- u_g_r (fk_userId,fk_groupId,fk_roleId)

my problem is that i would have a method on Group class that return the users of this group and theyr role (only roleId that is present in ternary association table... ) ....i would that is realized by hibernate with only query as: select users.userId,users.name,u_g_r.fk_roleId from u_g_r inner
join users on users.userId = u_g_r.fk_userId where u_g_r.fk_groupId = ?

...i try to use (in mapping of group)

<map name="users" table="`u_g_r`" cascade="none">
<key column="`fk_groupId`" not-null="true"/>
<map-key-many-to-many column="`fk_roleId`"class="it.test.Role"/>
<many-to-many column="`fk_userId`" class="it.test.User"/>
</map>

...or composite elements:

<set name="users" table="`u_g_r`">
<key column="`fk_groupId`" not-null="true"/>
<composite-element class="it.test.UserRole">
<property column="`fk_roleId`" name="roleId"/>
<many-to-one name="user" class="it.unitn.cs.hibernate.User" column="`fk_userId`"/>
</composite-element>
</set>

...but this realize n° query for retrieve user information (one for each user in u_g_r )...

I would that group contains an collection of UserRole; this class has two properties user and roleId... how realize this with Hibernate (populated this class with only query and not with n° query for each user!)?

Thanks in advance!

refer to

http://www.xylax.net/hibernate/ternary.html

Thanks...i've just read this article, but the proplem persist...
If i have the class:

A -> property idA , nameA (mapping on table a_example)

B -> property idB, nameB (mapping on table b_example)

C -> property idC, nameC (mapping on table c_example)

and it's present a relation table a_b_c whith fk_idA,fk_idB and fk_idC

Now i use the composite-elemen descript on article (in mapping of class A):

adding an get/set D method on A; where D is the class that rappresent relation (this has get/set B and get/set C method)

BUT if i load A and call getD the field D.B and D.C is not loaded (hibernate use lazy load and load this field only when i accessed they) the result is an query for all B and C present on D ...=(n° x 2) query where n is the number of B/C present for A in relation...

I would that Hibernate initialize it's with only query (because i use only the B.idB present in a_b_c and not all "Object" B)
like this:
select a_b_c.idB,c_example.idC,c_example.nameC from a_b_c inner join c_example on a_b_c.fk_idC = c_example.idC where a_b_c.fk_idA = ?
my composite element D must have only
idB and C fields....

It's possible realize this with Hibernate? Because if i more elements for A (m number) the query produced is (n° x 2) x m respect only 1 (because i don't use the all B object but only it' id that is present in ternary table...)!

Thank in advance
Alessio