Re: AW: [OJB-developers] Using CollectionDescriptor in repository.xml

[Thomas M. <tho...@ho...>]

Hi again,

Leandro Rodrigo Saad Cruz wrote:

> Sorry man, in fact the problem was in another line at repository.xml
> I defined a ReferenceDescriptor that pointed to the wrong class field.
>=20
>=20
> By the way. If I have a association like this A 1 ----- N B
>=20
> Do I have to defined CollectionDescriptors(from A to B) and
> ReferenceDescriptos( from B to A) or just one of them ??
>=20


Depends.
If you want to navigate from A to the Bs only you'll need a=20
CollectionDescriptor in ClassDescriptor A.

If you want to navigate from a B to its A only you'll need a=20
ReferenceDescriptor in ClassDescriptor B.

If you want to navigate in both directions you'll need both.

HTH,

Thomas


>=20
> On Fri, 2002-03-22 at 12:20, Mahler Thomas wrote:
>=20
>>Hi Leandro,
>>
>>I'll try to explain the 1-n section from the tutorial3.
>>Say you have a class ProductGroup with a Vector attribute allArticlesIn=
Group
>> that holds all Article objects belonging to this group.
>>
>>That is: *one* ProductGroup holds *n* Articles.
>>
>>You must tell OJB how to load the allArticlesInGroup attribute on loadi=
ng a
>>ProductGroup object.
>>This is done by the following CollectionDescriptor:
>><ClassDescriptor id=3D"2">
>>      <class.name>test.ojb.broker.ProductGroup</class.name>
>>	...
>>      <CollectionDescriptor id=3D"1">
>>         <cdfield.name>allArticlesInGroup</cdfield.name>
>>         <items.class>test.ojb.broker.Article</items.class>
>>         <inverse_fk_descriptor_ids>4</inverse_fk_descriptor_ids>
>>      </CollectionDescriptor>
>>	...
>>
>>This descriptor contains the following info:
>>- The class ProductGroup has a container attribute allArticlesInGroup.=20
>>  The Java-type of this attribute is not declared. It maybe of type
>>SomeType[],=20
>>  Collection, or ManageableCollection.
>>- The Items in this Container are of type Article
>>- The Mapping of class Article has a attribute with id=3D"4" that holds=
 a=20
>>  foreign key value idetifying the associated ProductGroup
>>
>>HTH,
>>
>>Thomas
>>
>>
>>>-----Urspr=FCngliche Nachricht-----
>>>Von: Leandro Rodrigo Saad Cruz [mailto:le...@ib...]
>>>Gesendet: Freitag, 22. M=E4rz 2002 15:30
>>>An: obj...@li...
>>>Betreff: [OJB-developers] Using CollectionDescriptor in repository.xml
>>>
>>>
>>>Hi all. There is one thing I didn't understand from the docs about
>>>association mapping
>>>http://objectbridge.sourceforge.net/tutorial3.html#1-n
>>>
>>><CollectionDescriptor id=3D"1">
>>>   <cdfield.name>collection</cdfield.name>=20
>>>   ******* -> does this field must be present in repository.xml in
>>>SomeCLASS ClassDescriptor ? or just be a field in SomeCLASS impl ?
>>>
>>>   <items.class>SomeCLASS</items.class>
>>>   <inverse_fk_descriptor_ids>2</inverse_fk_descriptor_ids>
>>></CollectionDescriptor>
>>>
>>>I keep getting exceptions like this :
>>>Expcetion : java.util.NoSuchElementException
>>>StackTrace: java.util.NoSuchElementException at
>>>ojb.broker.accesslayer.RsIterator.next(RsIterator.java) at
>>>ojb.broker.singlevm.PersistenceBrokerImpl.getCollectionByQuery
>>>(PersistenceBrokerImpl.java:931)at=20
>>>ojb.broker.singlevm.PersistenceBrokerImpl.getCollectionByQuery
>>>(PersistenceBrokerImpl.java:1000)at=20
>>>ojb.broker.singlevm.PersistenceBrokerImpl.getCollectionByQuery
>>>(PersistenceBrokerImpl.java:1093)at=20
>>>ojb.broker.singlevm.PersistenceBrokerImpl.getCollectionByQuery
>>>(PersistenceBrokerImpl.java:1080)at
>>>....
>>>
>>>that doesn't help me so much.
>>>
>>>
>>>--=20
>>>Leandro Rodrigo Saad Cruz
>>>IT - Inter Business Tecnologia e Servicos (IB)
>>>http://www.ibnetwork.com.br
>>>
>>>
>>>_______________________________________________
>>>Objectbridge-developers mailing list
>>>Obj...@li...
>>>https://lists.sourceforge.net/lists/listinfo/objectbridge-developers
>>>
>>>