RE: [ojb-users] references

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Any ideas?

********************************************
Steve Ebersole
IT Integration Engineer
Vignette Corporation 
512.741.4195

Visit http://www.vignette.com

********************************************

-----Original Message-----
From: Ebersole, Steven [mailto:ste...@vi...]
Sent: Wednesday, May 08, 2002 7:09 AM
To: 'Thomas Mahler'; obj...@li...
Subject: RE: [ojb-users] references

Below is the exception I get.  I appears that the exception occurs when
trying to resolve the reference to parent company when that fk column is
null.  If I remove that reference descriptor, everything works.

Query from class com.vignette.it.apps.dbapi.domain.CompanyDO where comp_id=
?
[DEFAULT] WARN: Please define a public constructor for class
com.vignette.it.apps.dbapi.domain.CompanyDO
with the following signature: (java.lang.Integer, java.lang.String,
java.lang.Integer).
It must initialize the classes persistent attributes. This is recommended to
increase performance but it's not mandatory!
[ojb.broker.singlevm.PersistenceBrokerImpl] ERROR: expected type: class
com.vignette.it.apps.dbapi.domain.CompanyDO
[ojb.broker.accesslayer.RsIterator] ERROR: null
java.lang.ArrayIndexOutOfBoundsException
        at
ojb.broker.metadata.ClassDescriptor.getFieldDescriptorByIndex(ClassDescripto
r.java:263)
        at
ojb.broker.metadata.ObjectReferenceDescriptor.getForeignKeyFieldDescriptors(
ObjectReferenceDescriptor.java:242)
        at
ojb.broker.metadata.ObjectReferenceDescriptor.getForeignKeyValues(ObjectRefe
renceDescriptor.java:264)
        at
ojb.broker.singlevm.PersistenceBrokerImpl.getReferencedObject(PersistenceBro
kerImpl.java:700)
        at
ojb.broker.singlevm.PersistenceBrokerImpl.retrieveReferences(PersistenceBrok
erImpl.java:517)
        at
ojb.broker.accesslayer.RsIterator.getObjectFromResultSet(RsIterator.java:263
)
        at ojb.broker.accesslayer.RsIterator.next(RsIterator.java:145)
        at
ojb.broker.singlevm.PersistenceBrokerImpl.getCollectionByQuery(PersistenceBr
okerImpl.java:900)
        at
ojb.broker.singlevm.PersistenceBrokerImpl.getCollectionByQuery(PersistenceBr
okerImpl.java:966)
        at
ojb.broker.singlevm.PersistenceBrokerImpl.getCollectionByQuery(PersistenceBr
okerImpl.java:1054)
        at
ojb.broker.singlevm.PersistenceBrokerImpl.getCollectionByQuery(PersistenceBr
okerImpl.java:1041)
        at TestOJBInstall.execute(TestOJBInstall.java:66)
        at TestOJBInstall.main(TestOJBInstall.java:53)
java.util.NoSuchElementException
        at ojb.broker.accesslayer.RsIterator.next(RsIterator.java:154)
        at
ojb.broker.singlevm.PersistenceBrokerImpl.getCollectionByQuery(PersistenceBr
okerImpl.java:900)
        at
ojb.broker.singlevm.PersistenceBrokerImpl.getCollectionByQuery(PersistenceBr
okerImpl.java:966)
        at
ojb.broker.singlevm.PersistenceBrokerImpl.getCollectionByQuery(PersistenceBr
okerImpl.java:1054)
        at
ojb.broker.singlevm.PersistenceBrokerImpl.getCollectionByQuery(PersistenceBr
okerImpl.java:1041)
        at TestOJBInstall.execute(TestOJBInstall.java:66)
        at TestOJBInstall.main(TestOJBIError occurred :
java.util.NoSuchElementException
nstall.java:53)

********************************************
Steve Ebersole
IT Integration Engineer
Vignette Corporation 
512.741.4195

Visit http://www.vignette.com

********************************************

-----Original Message-----
From: Thomas Mahler [mailto:tho...@ho...]
Sent: Friday, May 03, 2002 12:11 AM
To: Ebersole, Steven
Subject: Re: [ojb-users] references

Hi Steven,

Ebersole, Steven wrote:

> I am looking at switching from Castor over to OJB as it looks really
> promising in terms of its functionality (I especially love the use of
> virtual proxies here).  I did have two questions come up from my initial
> trials of OJB.
> 
> 1) Is it necessary to have both the foreign key and the foreign reference
> mapped and present on the object?  

depends on the navigibility between your persistent classes.
If you want to navigate from the 1-side to the n-side only, you just 
need a foreign key (and a ForeignKeyDescriptor).

If you want navigation from the n-side to the 1-side too, you'll also 
need a reference attribute (and a ReferenceDecsriptor too).

In the examples, the relation between
> Article and ProductGroup is the example From which I was working.  There,
> Article has two attributes dealing with its relation to a ProductGroup,

Yes, because we have navigation from ProductGroup to all its Articles 
and from an Article to its associated ProductGroup.

> productGroupId (which is the DB fk field) and productGroup (which is an
> instance of the ProductGroup object to which productGroupId referes).  Is
it
> necessary to do this, or is there a way to have the Product object only
know
> about its related ProductGroup?

No, because ProductGroup and Article have a 1:n relation the table 
representaing Article entities *must* have a foreign key to identify the 
associated ProductGroup.

> 
> 2) I mapped a relationship, uing my classes, similiar to the above
> relationship (it is a company -> parent company relationship).  However, I
> get exceptions if a particular company did not have a parent company (its
> PRTN_COMP_ID column on the DB is NULL).  Is there something additional I
> have to set up in the mapping to define that side of the relationship as
> optional?  Below is the mapping I have for this:
> 
> 
>     <ClassDescriptor id="2">
>
<class.name>com.vignette.it.apps.dbapi.domain.CompanyDO</class.name>
>         <table.name>COMPANY</table.name>
>         <FieldDescriptor id="1">
>             <field.name>id</field.name>
>             <column.name>COMP_ID</column.name>
>             <jdbc_type>INTEGER</jdbc_type>
>             <PrimaryKey>true</PrimaryKey>
>         </FieldDescriptor>
>          ...
>         <FieldDescriptor id="5">
>             <field.name>parentCompanyId</field.name>
>             <column.name>PRNT_COMP_ID</column.name>
>             <jdbc_type>INTEGER</jdbc_type>
>         </FieldDescriptor>
>         <ReferenceDescriptor id="1">
>             <rdfield.name>parentCompany</rdfield.name>
>  
>
<referenced.class>com.vignette.it.apps.dbapi.domain.CompanyDO</referenced.cl
> ass>
>             <fk_descriptor_ids>5</fk_descriptor_ids>
>         </ReferenceDescriptor>
>    </ClassDescriptor>
> 

Your mapping seems OK. This must be an OJB bug! Can you provide me with 
a full stacktrace ?

thanks,

Thomas

> 
> Thanks
> 
> 
> 
> 
> ********************************************
> Steve Ebersole
> IT Integration Engineer
> Vignette Corporation 
> 512.741.4195
> 
> Visit http://www.vignette.com
> 
> ********************************************
> 
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