Hi. I'm having some trouble with an unidirectional many-to-many mapping using a join table. After reducing to the simplest possible case the problem remains, so I guess I got something wrong concerning these mappings.

As mentioned below, I have two classes, A and B. A contains several associations on B, this should happen in a seperate join table. I adapted the example from the manual (at least I think so), but no entry in the join table is made.

My code is just the following:



If I execute this, a and b get inserted, but no entry in the join table is made.

So how is this supposed to work?

Thanks in advance.


Hibernate version: 3.0

Mapping documents:

A.hbm.xml::


B.hbm.xml:


Name and version of the database you are using: MySQL 4.1

Hello Martin;

I had just come out of such set of problems with one-to-one and one-to-many. You need to make the mapping bi-directional.

In your add method for class A should be

bSist would be any kind of collection that you are using to persist the b objects

addChild(B b){
b.setA(this);
if(bSet==null){
bSet = new HashSet();
}
bList.add(b);
}

change your a mapping to look something like this: added inverse= "true"

<hibernate-mapping>
<class name="de.bebit.blackbook.test.A" table="test_A">
<id name="id">
<generator class="native"/>
</id>
<set name="children" table="test_A_B" cascade="all" inverse="true">
<key column="a_id"/>
<many-to-many column="b_id" class="de.bebit.blackbook.test.B"/>
</set>
</class>
</hibernate-mapping>



also try setting the unsaved-value="any" for in mapping of B such as
add a setter and getter for "a"


<hibernate-mapping>
<class name="de.bebit.blackbook.test.B" table="test_B">
<id name="id" unsaved-value="any">
<generator class="native"/>
</id>
<many-to-many cascade="none" name ="a" column="b_id" insert ="false" update = "false" class="de.bebit.blackbook.test.A"/>
</class>
</hibernate-mapping>

for reference you can look at an example for many-to-many given in this tutorial. I belive doing all these should solve your problem


http://www.warfrog.com/hibernatetutorial2/

Thanks for your help, but it didn't help me :(

But finally, I got the error. I didn't use transactions in my example, and either did I flush the session, I thought saving the objects would be enough, but it wasn't!

Now I flush the session afterwards, and the association is made. Whether I use uni- or bidirectional association btw doesn't change anything, at least not in this case.

So, problem solved.