Re: custom metatdata attributes

Jakob Praher wrote:
> hi all,
> 
> as we (Leo and I) have talked about custom metadata attribute support
> for java lately, I wanted to know whether this should be done inside
> avalon, or should be delegated to another (jakarta) project.

according to KISS, it should be a standalone library. There's lots of 
locations where something like that can be done. Sice Jakarta Commons 
already has some stuff regarding this in their sandbox I figured we'd 
start there.

> if inside avalon, I was wondering what approach towards implementing
> them should be taken. (class augmentation, manifest files, ...)

I'm leaning towards parsing of

/** @attribute SomeClassNameAttribute("blaat") */
class MyClass

where an ant+qdox solution is run over this at build time. Such an 
AttributeParserTask could generate lots of stuff. The most important 
thing to agree on the syntax of the source files; you can always plug in 
lots of different generators.

I would probably be most comfortable with this ending up in an xml file 
coupled to the class, ie something like:

MyClass.attributes
------------------
<attributes>
	<attribute
		class="SomeClassName"
		target="class">
		<constructor>
			<string value="blaat"/>
		</constructor>
	</attribute>
</attributes>

or maybe adopt the SOAP serializers from Axis for generation of 
everything inside <attribute/>. Something like that. (I believe .Net 
uses SOAP for serialization by default.) That's mostly because it is 
consistent with the approach avalon currently takes.

> I am curious about your opinons,

me too :D I am actually waiting for a reply from some of the people 
who've done a lot of the meta/attribute stuff currently in place @ 
avalon, in particular Peter Donald (hi pete!). I suspect he's still 
catching up wrt e-mail...holidays y'know.

> and I am interested in helping with the
> implementation.

That'd be neat! If you feel like getting started, the easiest thing to 
do is to probably check out jakarta-commons-sandbox, take the attribute 
code in there and run with it, then send patches to the commons list. 
I'm still orienting myself (still need to take a look at qdox/xdoclet 
first).

The alternative is to try and drag requirements out of a broad group of 
people (I suspect potential interest is big :), but I'm guessing that's 
going to be difficult given the rather 'distributed' nature of that group.

We'll go with the flow from there (I haven't been particularly active in 
commons before, but I believe I have commit rights to commons sandbox, 
so if there's no response it's probably okay for us to work on it there).

cheers,

- Leo