[I accidentally posted this as a reply to a previous topic. Sorry]

Can someone please provide an example ternary mapping of tables A, B and C though the join table ABC.

I'm looking for something like this,



Any suggestions?

Thanks,
-Mitch

P.S. I have seen the example in the Reference Document and searched the forum, but still can't figureout the syntax.

You have two choices:

* use a Map with an <index-many-to-many>
* use a <composite-element>

which do you want?

I'm not sure of the difference (sorry).

Can you give an example of the Map with <index-many-to-many>?

I'm not sure how difficult that is, I haven't had any luck yet. :)

Thanks for responding.

-Mitch

Maybe a better question is whether there is a better tutorial on mapping than the Hibernate2 Reference Documentation. I've gone through that a couple of times now, front to back and still don't grasp anything but the simplest of mappings.

Any suggestions?

-Mitch

By way of an example, here is my ternary association betwen groups and the various entitlements that group has to system use cases.


So on my SecurityGroup class, I can lookup the groups entitlement to a given use case by doing

In my system, use cases and entitlements are enums, hence the special types in the map mapping. If you want simple types, say strings, the mapping is even easier:


HTH

Further, say for your association diagram you have classes: ClassA, ClassB, and ClassC. Assume that ClassA and ClassB are already mapped. Then in ClassC you want to map the association represented by ABC:

Is the assumption then that similar mappings exist for tables 'A' and 'B'?

Specifically,


I apologize if this is a naive question.

I'm going to test it as soon as I get a chance, but if someone knows off the top of their head, that would be nice.

Thanks,
-Mitch

Depends what you mean by "similiar". Certainly ClassA and ClassB must be mapped. They dont necessarily have to have understanding of the ternary association in which the participate with ClassC if you don't want them to.

Hi-,
I'm a newbie trying to grasp the concepts of ternary association in hibernate. I want to know how do you map the same scenario with composite element. i went throught he examples in doc. but still i'm not grasping the concept as i'm new to the persistence(DB) side also.If you can expalin it that will be helpful.

Thanks

Hans

I'm sorry, but I haven't attempted ternary associates via composite elements. After spending a couple of days finding out that cascading saves don't apply to the key of a ternary mapping, I simply got things working the best I could and moved on.

I was able to get my ternary relationship mapped sufficiently (though not optimally IMHO).

...which leads me to the following tangent:

Hibernate leaves *much* to be desired in terms of documentation. Hopefull at some point Gavin et al. will realize that whatever magic he/they develop may be useless without sufficient documentation.

My experience has been that if you live/eat/breathe Hibernate, it is a very effective tool. But for a casual user, who also needs to tend to architecture, GUI, build processes, etc. and want's to use Hibernate to simplify/eliminate data mapping from their already full plate, Hibernate is a bit of a time sink.

I attribute this solely to poor documentation rather than poor design or lack of features.

As long as everything is working fine, I love Hibernate. But as soon as I get that inevitable email that some of the data isn't mapping properly, I get that sinking feeling that I'm about to invest another significant amount of time trying to 'guess' what Hibernate wants me to do next.

...sorry for sidestepping your original question. :)

-Mitch

I'm trying to update the 3 columns of a ternary association and it does not work for the index and element columns, your right! You wrote : "I simply got things working the best I could and moved on. "
May I ask how you "got things working the best"?
Thanks
Ced

I originally wanted my primary object to have a Map, the key of which related to one table, and the value to another. As I said earlier, cascading saves *only* work for the 'value' not the 'key'.

Pictorially, my 'optimal' solution looks like this,


Unfortunately, saving A cascades the save to D but not C (the Map key).

My solutions was to the move the ternary mapping to a fourth object.

Since I can't relate A directly to C and D with a Map in A, I had to create a new B object who's sole purpose is to relate A, C and D. Then I added a java.util.List of B objects to my A object.

Pictorially, my solution looks like this.


My B has a primary key and a reference to an A, B and C object.

With this approach, I am able to cascade saves throughout.

-Mitch

create table abc(
a_id VARCHAR2(32) not null,
b_id VARCHAR2(32) not null,
c_id VARCHAR2(32) not null,
primary key (a_id, b_id)//(a_id,b_id,c_id)
);