Hi all,

I have a case as follows:

Table A and table B have many-to-many relationship. The association table AB has (extra) nullable attributes. I tried to use "composite-element" as follows:

AB is modelled as a composite element in A. AB has reference to B.

Now if I delete an entry of AB from A, corresponding entry from table B is not deleted. The cascade="all" option doesn't work in this case.

What could be the reason?
Also can u suggest any other way to model this relationship?

Thanks in advance
-Reshma





Need help with Hibernate? Read this first:
http://www.hibernate.org/ForumMailingli ... AskForHelp

[b]Hibernate version:[/b]

[b]Mapping documents:[/b]

[b]Code between sessionFactory.openSession() and session.close():[/b]

[b]Full stack trace of any exception that occurs:[/b]

[b]Name and version of the database you are using:[/b]

[b]The generated SQL (show_sql=true):[/b]

[b]Debug level Hibernate log excerpt:[/b]

You dont need such modeling, many-to- many is handled in database.
You need A object, B object and AB table where A's id and B's id are foreign keys. Then just map as simple <many-to-many> mapping with cascade property.

Hi,

Thanks for your reply.

As i mentioned in my first post, i have a case where my "association table has nullable attributes". "many-to-many" relationship doesn't support that.

This case is handled by "composite-element". But it dosen't permit cascade delete operation as a component is of "value-type".

So i cannot use composite-element either.

can you think of some other way to model this relationship.
Please reply As soon as possible ... (have a deadline to meet :-) )

Hi,

my problem is solved. It worked successfully with a combination of
A AB A
one-to-many many-to-one

and lifecycle methods.
Thanks again

Hi Reshma,
I have your same problem.
Can you post the part of the mapping you used for this?

I have 3 tables, and the association table has one attribute.

I'd like to map this with just 2 classes: one main class with a collection of elements whose data is taken from a "join" of the association table and the last table.

Thanks for any suggestion.

Bye

Lorenzo

Hi Lorenzo,

In this case if you want to have just 2 files, then you will have to use composite-element tag. But it has some disadvantages
1. Your mapping table cannot have nullable attributes else hibernate fails.
2. If you want cascade delete effect, this cannot be achieved. I tried only
insert case and it worked with it. But delete didn't work (since
composite-element is of value type).

mapping file of 1st class,

<composite-element class="(name of association class)">
<property name="attribute1" />
<many-to-one (entry for 2nd class)>
....
....
</many-to-one>
<composite-element>

The association table won't have mapping file but will have a java class. That class should have object of 2nd class and additional attributes if any.

Reference:
http://docs.jboss.org/ejb3/Hibernate3/r ... ml_single/
8.2. Collections of dependent objects

hope this answers your question.

Thank you for your prompt reply, I'll try as soon as possible...maybe on monday ;)


Ciao

Lorenzo