Patrick-
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) <[EMAIL PROTECTED]> 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
