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From Marc Prud'hommeaux <>
Subject Re: Preliminary design for supporting OpenJPA annotations in XML metadata.
Date Wed, 25 Jul 2007 02:45:04 GMT

That's precisely what I had envisioned. In theory, all we'd need to  
do is provide a means to override the mechanism by which we obtain  
the annotations, and it might just magically work.

This does presume that the hierarchy of the JPA-standard annotations  
matches the hierarchy of the JPA-standard XML elements. I haven't  
checked this, but I would expect this to be the case.

It would also simplify the XML-trumps-annotation logic, since the XML  
parser would just default to the superclass' annotations if it is not  
overridden by an XML element.

On Jul 24, 2007, at 5:03 PM, Patrick Linskey wrote:

> I haven't read David and Marc's most recent emails, but here's an idea
> that I've been toying with in terms of unifying annotation and XML
> parsing: annotations are interfaces, so presumably we can create new
> instances of types that implement them somehow. (Maybe the JVM
> prevents this; I haven't tested.) If so, then we could just have a
> single annotation parser, and have the XML parser generate annotations
> to pipe into the annotation parser.
> I'm not sure if that gets us anything, but it might be an interesting
> direction to explore.
> -Patrick
> On 7/20/07, David Ezzio (asmtp) <> wrote:
>> Hi,
>> I'm starting to design support of XML metadata for OpenJPA  
>> annotations
>> in order to address OpenJPA-125 and OpenJPA-87.
>> I've attached a zip containing a preliminary design document, a  
>> sample
>> openjpa_orm_1_0.xsd file and a sample OpenJPA ORM instance.
>> It took quite a while to create the text document and it is best  
>> viewed
>> as the tracks of a design process.  The design that I worked on  
>> the most
>> (the one with the most documentation) is not necessarily the best
>> design.  There are two alternatives suggested, and there may be  
>> others
>> that I haven't thought of.
>> I think the fundamental choices facing us are these:
>> 1. Do we construct an OpenJPA ORM schema that extends the JPA ORM
>> schema?  Doing so, allows the user to use one metadata file  
>> instead of
>> two, and will enhance maintainability for our users'  
>> applications.  Or
>> do we construct a standalone OpenJPA ORM schema?  I've chosen the  
>> first
>> option in the preliminary design, and I think it is the best choice.
>> 2. Do we use a syntactically loose "extension" element format or  
>> do we
>> construct new elements for each supported annotation?  Choosing the
>> first makes it easy (I think) to support newly added annotations.
>> Choosing the second allows the schema validator to do most of the
>> validation work.  I've chosen the first option in the preliminary
>> design, but I'm not at all sure of the choice.
>> 3. Do we envision support in XML for all OpenJPA annotations or  
>> for only
>> a subset?  If a subset, how do we draw a bright line that will be
>> consistent and easily documented and followed over time?  I've chosen
>> the first option in the preliminary design simply because that is the
>> brightest line that I can think of and because it gave me a chance to
>> look over the field of OpenJPA annotations.
>> I'll be off on vacation for a week with very limited Internet
>> connections, so please, take as much time as necessary to consider  
>> the
>> design, and carry on some discussions without me if the spirit  
>> moves you.
>> Thanks,
>> David Ezzio
> -- 
> Patrick Linskey
> 202 669 5907

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