Re: [jboss-as7-dev] Metadata for AS
On 2/21/11 1:22 PM, Andrew Lee Rubinger wrote:
Alongside our metadata discussions this morning, I'd like to
offer up a
prototype for use as the preferred metadata view for AS subsystems.
-snip-
The purpose of the project is to define an object model for
specification and JBoss-specific metadata, with the following driving
tenets:
One of the problems of any kind of metadata project, is that the scope
is somewhat vague. It can be anything from just spec descriptors all the
way to the entire runtime state of server deployment. Without a clear
scope, it will likely feature creep towards the latter.
* No compile dependencies outside the JDK
* Pluggable backends (ie. DOM, XB, Stax, right now we use DOM and
straight hardcoded parsing logic)
Why bother with pluggable backends? In particular whats the point of
having both a DOM parser AND a STAX parser?
* Easy import/export to/from File/URL/String/Stream/bytes
Other concerns are to be addressed at another level, namely:
* Merging
* Annotation scanning repo output> object model view
* Validation
* ...basically anything initiated during deployment.
This is a good start on specifying a scope. It sounds like an attempt to
do a saner JSR-88 framework.
One of the challenges of using something like this for annotation
processing is the assumption that there is a one-to-one relationship
with annotations and configurable xml. This is not always the case. CDI
for example has a large number of annotations to process that are only
relevant to the actual CDI engine itself. This is not to say that there
could not be value in some kind of xml override mechanism (originally in
the draft specification), just that the consumers of interest are rather
limited (just weld cares about this information). Also you probably
don't want to have something that produces annotation java output.
Deployment logic should be, IMO:
Deployer takes in deployment> Gen object model> calls outside layers
for merging/validation/etc> deployer installs final view
That seems inline with
what we have at the moment. The key thing though
is that a deployer's state be allowed to evolve at the same pace as the
deployer.
--
Jason T. Greene
JBoss, a division of Red Hat