Re: Strange null pointer exceptions

[Jan Berkel]

Hi Olli,

[EMAIL PROTECTED] wrote:

since the NPE is due to missing fields in the metadata,
I assume that a workaround is to add field-descriptors.
I added field-descriptors to the class descriptor of the Interface 
(Template) and it worked fine, thanks.

Actually you need field-descriptors in your Interface and implementing 
class, not in the base class itself (as there can be no instances ?).

I think the documentation on the ojb website is not very clear or even 
erroneous on this point.

<SNIP from http://db.apache.org/ojb/tutorial3.html#extents>
   1.  A declaration for InterfaceArticle, defining which classes 
implement this interface:

<!-- Definitions for org.apache.ojb.broker.InterfaceArticle -->
   <class-descriptor class="org.apache.ojb.broker.InterfaceArticle">
      <extent-class class-ref="org.apache.ojb.broker.Article" />
      <extent-class class-ref="org.apache.ojb.broker.BookArticle" />
      <extent-class class-ref="org.apache.ojb.broker.CdArticle" />
   </class-descriptor>
</SNIP>
It doesn't give a hint to include field-descriptors for the interface, 
or does my setup just happen to be special ?

Moreover, having the obligation to add field descriptors to the 
interface is not very practical when using the xdoclet-ojb module (where 
you have to define the mappings on the instance fields), or is there a 
workaround ?

regards,
 Jan
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