Re: Problems saving a m:n relationship

[Armin Waibel]

Stijn de Witt wrote:

Hi Armin, all,

I have tried your solutions, but I ran into a problem, because I was working
with rc4. ojb rc4 doesn't have the .link() method in the ServiceBrokerHelper
yet.
So I downloaded rc6, ran the ojb-blank target, inserted my files and created
a rc6-version of my project. I got it all to build, but at the first
ojb-related query, I get this in my logging window:
15:52:11,531 INFO  [BaseSubmitter] handleSubmit: Getting persistence
broker...
15:52:12,031 INFO  [STDOUT] [BOOT] WARN:
15:52:12,031 INFO  [STDOUT] Value
"org.apache.ojb.odmg.collections.DListImpl_2" is illegal for key
"OqlCollectionClass" (should be a class, using default value
org.apache.ojb.odmg.collections.DListImpl)
15:52:12,359 INFO  [STDOUT] [DEFAULT] ERROR:
15:52:12,359 INFO  [STDOUT] **
org.apache.ojb.broker.metadata.RepositoryTags: Tag 'object-cache' is not
defined. **
Does this mean anything to you?

this sounds like a classloader problem. Do really replace all ojb-jar 
files (and config files) in your app classpath?

regards,
Armin

Thanks,
-Stijn
----- Original Message ----- 
From: "Armin Waibel" <[EMAIL PROTECTED]>
To: "OJB Users List" <[EMAIL PROTECTED]>
Sent: Friday, April 09, 2004 2:00 PM
Subject: Re: Problems saving a m:n relationship



Hi Stijn,

a few days ago I wrote some tests for M:N handling in odmg-api and
stumble across the same problem (hope we can fix this soon). There are
two possible workarounds:
Transaction tx = odmg.newTransaction();
tx.begin();
Iterator it = person.getAddresses().iterator();
while(it.hasNext())
{
   database.makePersistent(it.next());
}
database.makePersistent(person);
tx.commit();
or you can use the pb-api to insert your object (this looks a little bit
complex, because you have to set auto-update/delete false when using
odmg-api):
TransactionExt tx = (TransactionExt) odmg.newTransaction();
tx.begin();
PersistenceBroker pb = tx.getBroker();
Iterator it = person.getAddresses().iterator();
while(it.hasNext())
{
   pb.store(it.next());
}
pb.store(person);
pb.serviceBrokerHelper().link(person, true);
tx.commit();
Hope this will help you.

regards,
Armin
Stijn de Witt wrote:


Hi,

I have a problem trying to persist two objects that are related through
an indirection table. This is what my tables look like:

-----
PERSON
id
firstname
lastname
...
ADDRESS
id
street
housenr
...
PERSON_ADDRESS
person_id
address_id
-----
I have chosen for this construction, because COMPANY can have multiple
addresses too, so I don't want a column person_id in ADDRESS. One address
doesn't have to be available for multiple PERSON's or COMPANY's or whatever,
so it actually is more of a 1:n relationship using an indirection table. So
PERSON_ADDRESS will often contain the same person_id multiple times, but not
the same address_id.
I've read the tutorials, but I don't get it to work. I'll show (a
fragment of) our repository_user.xml:

-----
<class-descriptor
   class="nl.bergland.codamo.Address"
   table="bit_Address"
   <field-descriptor
       name="id"
       column="id"
       jdbc-type="INTEGER"
       primarykey="true"
       length="11"
   >
   </field-descriptor>
   <field-descriptor
       name="street"
       column="street"
       jdbc-type="VARCHAR"
       length="64"
   >
   </field-descriptor>
   <field-descriptor
       name="houseNr"
       column="houseNr"
       jdbc-type="VARCHAR"
       length="16"
   >
   </field-descriptor>
</class-descriptor>
<class-descriptor
   class="nl.bergland.codamo.Person"
   table="bit_Person"
   <field-descriptor
       name="id"
       column="id"
       jdbc-type="INTEGER"
       primarykey="true"
       length="11"
   >
   </field-descriptor>
   <field-descriptor
       name="firstName"
       column="firstName"
       jdbc-type="VARCHAR"
       length="24"
   >
   </field-descriptor>
   <field-descriptor
       name="lastName"
       column="lastName"
       jdbc-type="VARCHAR"
       length="24"
   >
   </field-descriptor>
   <collection-descriptor
       name="addresses"
       element-class-ref="nl.bergland.codamo.Address"
       indirection-table="bit_PersonAddress"
       auto-retrieve="true"
       auto-update="true"
       auto-delete="true"
   >
       <fk-pointing-to-this-class column="personId"/>
       <fk-pointing-to-element-class column="addressId"/>
   </collection-descriptor>
</class-descriptor>
-----
The generated tables in mysql seem to be ok with me (we actually use
OjbDoclet to generate the repository.xml and the SQL) and insertion of a
PERSON works fine. However, when we create a new person, add a new Address
to it and try to save the person, the following happens:
A new record gets created for PERSON fine
A new record gets created for ADDRESS fine, but when I set auto-update
to true, 2 get created??

A new record gets created for PERSON_ADDRESS, but both the columns
person_id and address_id are set to 0.

Our save code looks something like this:

-----
       Person person = new Person;
       person.getAddresses().add(new Address());
       Implementation impl = OJB.getInstance();
       Database db = impl.newDatabase();
       db.open("default", Database.OPEN_READ_WRITE);
       Transaction tx = impl.newTransaction();
       tx.begin();
       // establish database locks on all root dataobjects
       tx.lock(person, Transaction.WRITE);
       // set person and address values
       // ...
       tx.commit();
       db.close();
-----
A lot of info for a first-time post, I hope this problem sounds familiar
to someone here.

Thanks,

-Stijn


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