> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Geir
> Magnusson Jr.
>
> Paulo Gaspar wrote:
> >
> > Geir,
> >
> > Took sometime to get back at this (an interesting movie on TV).
>
> Me too! I went to see "Crouching Tiger, Hidden Dragon." Great movie.
> Sorry to run off like that.
No problem. Then it also got late for me.
> > Ok, there is a single point for introspection call which is from:
> > ASTIdentifier.doIntrospection( Class data )
>
> We do it in a few other places as well. Yes, it might be good to bring
> those together into one place, but this is a very expensive aspect of
> Velocity's operation, so we need to be careful.
Sure, but I only found this point as a start to discovering properties.
I might be missing something but it was what I found using some searches.
Can you give me some pointers here?
> > Now, having:
> > public interface IntrospectionBuilder
> > { public AbstractExecutor doIntrospection( String identifier,
> Class data )
> > throws Exception;
> > }
> >
> > and an extra field for the Parser class like:
> > public final IntrospectionBuilder introBuilder;
>
> Why the Parser class? The parser has nothing to do with this - there is
> nothing static about this : a parsed template must be able to be used by
> multiple contexts at the same time. By this I mean nothing at parse
> time dictates the introspection information. My servlet using a parsed
> template can use an object with a method getFoo(), and your servlet
> using the same parsed template can use an object with a hashtable with
> "Foo" as a key, and if the template has $ob.Foo, we both are happy.
> This feature is one of the most powerful and beautiful, I think... :)
The parsed template would still be able to be used by multiple contexts at
the same time. The Parser is just a convenient holder for the reference to
the IntrospectionBuilder which avoids extra references. It also opens the
possibility of creating a parser that works with a different discovery rule
from the rest of the parsers... but I digress a bit here.
> > one could replace the introspection call (in ASTIdentifier.execute()):
> > executor = doIntrospection( c );
> > by
> > parser.introBuilder.doIntrospection( identifier, c );
>
> Sure. Still wondering about the parser bit though.
>
> > Profits:
> > The possibility of having plugable introspection, even per Parser.
>
> I see the benefit of pluggable introspection just for the modularity
> alone, although I wouldn't be thrilled about including in the vel
> distribution anything but a 'standard' introspection module, just for
> sanity's sake, and to avoid encouraging people from doing things like
> accessing things they shouldn't. 'public' and 'private' are there for a
> reason :) Of course, that would be up for a general vote, I guess.
Sure. I also think that only the standard introspection module should be
mounted. Anything else is a customization. At most one could provide a
sample for documentation purposes.
I already stated before: "The one thing that seems to make sense is to keep
Velocity with a standard discovery mechanism as much compatible as possible
to the beans standard, while allowing people to plug their own mechanism at
Run Time."
> > Costs:
> > - An extra member, and its initialization, for the Parser class. Since
> > a pool of such objects is used, this is a very low cost.
> > - A couple of extra references and an extra parameter to create the
> > introspection. This is not such high cost either.
>
> Yes, after thinking about it, there prollie wouldn't be much cost to it.
=:o)
> > Well, actually, maybe this costs less than keeping and initializing that
> > "method" field (in the ASTIdentifier class) that is not being used any
> > more.
> > =;o)
>
> Yes, that's just a leftover. Not sure how that relates here.
Doesn't. It was just something I found while researching this. Since it
really has some cost, I am mentioning it so that some one can remove it.
I do not pretend this is a justification for the plug in thing. That is why
I used the smiley. (Ok... maybe I had a bad choice of words.)
So, if you give me some pointers on the other starting points for
introspection that I am missing, I can code something as above and give it
back to you. Sample included.
Have fun,
Paulo
