Re: [j-devel] How to subclass and callback?

[Luke H. <ruk...@gm...>]

Hi all,

I recently posted these two questions:

> > 1. How do I subclass java classes with lisp code? I presume it'd be
> > similar to %jnew-proxy, but I can't find a function that does it.
> >
> > 2. How do I make these subclasses/interfaces available to be called
> > from java source code (i.e. callbacks)?
> >
Andras forwarded me some sample code on the usage of
"jnew-runtime-class", which efficiently answered the first question.=20
However, the second question seems to me to be quite tricky, but I
think it's worth solving, because then I could redevelop "in place"
classes which were initially written in Java and replace them
piecewise with Lisp code.

I've thought of a possible solution for the second question.  The
solution comes in two parts: first keeping javac happy so you can
compile the java source, and second keeping java itself happy.

Satisfying javac should be easy, just create java stub code (probably
autogenerated).

Satisfying java seems hard.  I briefly (and naively) thought that the
class output of jnew-runtime-class would work, but of course it
doesn't (presumably because the Lisp environment itself doesn't get
booted, and it's doubtful that the class file saves the lexical
environment in which the runtime class is defined anyway).

So my next thought is implementing, say, an ABCLClassLoader, which
initialises Lisp, and then instead of looking for the class foo.Bar by
resolving foo/Bar.class, looks for foo/Bar.abcl or foo/Bar.lisp which
contains code which creates the runtime class foo.Bar.

I had a quick look at the abcl source and noticed there's a
"JavaClassLoader.java" I couldn't work out what it did, and a grep
told me that it wasn't called by anything else.

1. Am I missing a really simple solution?
2. Any Lisp complications I may have overlooked?
3. What's the minimum amount of abcl code I need to execute to boot
lisp and Load other files?  I've looked at Interpreter.java, but I
don't quite know whether I need to have a toplevel, etc.
4. Any ClassLoader complications I may have overlooked?

Sorry if this is a bit newbie-ish, but I haven't dug this deep in Java
before, and I feel it's probably better to ask questions first and not
waste my time re-inventing the wheel.

-Luke

P.S. for jnew-runtime-class, am I correct in assuming the method
implementations are full closures?