Re: [eclipselink-users] programmatic customization of mapping meta-data

[Olaf Otto <olaf@xxxxxxx>]

Hi Tom,

Thank you for your reply.

Tom Ware wrote:
> Hi Olaf,
>
>   What kinds of things do you want to do in your meta-data modification?
I think it will mostly be modifying the mapping type of certain fields 
(for example changing it from basic to N:N or a custom mapping), 
excluding fields etc.
>   Depending on what you want to do, there may be several ways to make 
> modifications to the metadata.
>
> 1. There is a Customization mechanism that allows you to customize the 
> mappings that are created by our meta-data processing
Very interesting - which specific mechanism are you referring to?
> 2. There is an event mechanism the provides you with callbacks at 
> certain stages of our initialization
I have seen the event mechanism - but will this actually work before the 
meta data of the entities has been processed?
> 3. You can specify your mappings in XML. (with the option of having 
> the XML be the only source of mappings)
I know, but this is not an option, since this would require custom 
mappings for framework users affecting fields they cannot see. 
Furthermore, the fields are subject to a lot of changes when altering 
classes. Basically, i must identify the generated fields by a certain 
prefix and handle them with regard to their content.
>   You should also be aware that some performance features in 
> EclipseLink are enabled by byte-code weaving.
Indeed, i have seen that using the eclipse agent has a lot of 
advantages. But there are a lot of complications with java agents and 
the framework i don't wish to address by now.
> -Tom
Regards,
Olaf

> Olaf Otto wrote:
> > Hello eclipse users!
> >
> > I have a framework that makes massive use of aspect-oriented 
> > programming and code generation. This includes a significant amount 
> > of additional fields being created in various classes (of a project 
> > using the framework, not in the framework itself) by a java agent at 
> > class loading time.  These fields are primarily generated for 
> > internal framework purposes and are thus invisible to a framework user.
> >
> > Most of these fields are references to non-serializable resp. custom 
> > types and must be handled in a non-standard fashion for persistence.
> >
> > Now here is the question: Is there a way to hook into the meta-data 
> > processing occurring during predeployment? More precisely, i would 
> > like to access and modify the persistence meta-data of entities 
> > before processor.processORMMetadata() is invoked in the 
> > processORMetadata of the PersistenceUnitProcessor class.
> >
> > Thank you and regards,
> > Olaf
> >
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