[Jython-users] Big Question

[Adam B. <sir...@ya...>]

Well, I've been playing with Jython a bit, and I still
don't fully understand it. I'm even sad to say that I
find the javadoc sadly lacking. I'm hoping, then, that
some more knowledgable person can take pity on me and
give me a hand. I'm going to describe what I want to
do, in as much detail as I can think of, and I'm
hoping someone can explain how to do it.
 
I have a class written in Java with a few methods
defined. I want the user of my program to be able to
extend this class in Jython by writing a .py file with
a
known name. Then, when a certain event occurs in my
program, I wish to load this class (including
reloading it, if it has changed since the last time we
used it), instantiate it, and call a method with a
known name/signature (that is, one of the methods
defined in the parent class). In addition, since there
will be multiple python files floating around (that
is, the user can define more than one class in python,
although they all will extend the same java base
class), I want
to make sure there are no side effects; that is, I
don't want definitions and such to hang around between
calls to python classes.
 
How should I even begin to do this? I don't know
whether it is better to compile or interpret, in this
case, even. Speed is actually a relatively important
factor, which is a point for compiling, but only if
there's a way to recompile and reload classes without
restarting the VM (preferably a prettier way than the
usual hack for doing this in java). On the other hand,
while interpreting seems easier at first, I can't find
a way to enforce the contract that the .py file
contain only a class, and nothing else. Also, unless
we create a new interpreter each
time (which may, I wouldn't be surprised, take longer
than just recompiling a class), I don't see a way to
guarantee no side effects between calls.
 
Whatever help or advice you can give would be
appreciated. The more low-level (pseudocode, example
code, whatever) the better. I'm 95% sure that what I'm
asking for is possible, and 100% sure it should be
possible, so if I find out that it's not, for whatever
reason, I do intend to hack Jython until it is. If I
end up
doing this, I really will need all the detail I can
get, before I try to grok the code on my own.
 
Adam Berger

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