RE: [Jython-dev] Py.java2py

[brian z. <bz...@zi...>]

The reason I ask is I have some code which wants to iterate an instance
using __len__ and __finditem__ magic methods on any sequence.  I'll accept
anything with those two methods and I thought the Collection classes where
wrapped as such (thus my previous question about CollectionProxy; after
thinking about, it makes sense as to why Java classes come in as
PyJavaInstance instances.).  In the meantime I do this:

protected boolean isSeq(PyObject object) {
	if(object instanceof PyJavaInstance) {
		List list = (List)object.__tojava__(List.class);
		if(list == Py.NoConversion) {
			return false;
		}
		object = new PyList((PyObject[])list.toArray(new PyObject[list.size()]));
	}
	return object.__findattr__("__finditem__") != null &&
object.__findattr__("__len__") != null;
}

I'll look into writing the Java->Python wrapper factory and the developers
can do what they want with it.

As for subclass support, would not Class.isAssignableFrom(Class) be
sufficient for handling these cases.    I'm thinking of this off the top of
my head so I'll have to test it out first.

thanks,

brian

-----Original Message-----
From: jyt...@li...
[mailto:jyt...@li...]On Behalf Of Finn Bock
Sent: Tuesday, February 27, 2001 7:03 AM
To: jyt...@li...
Subject: Re: [Jython-dev] Py.java2py


[brian]

>The method Py.java2py does not support all clases and is closed to the end
>user.  I would like to add functionality for classes such as BigDecimal to
>have Python wrappers, but don't want to endlessly patch the core.  Has
there
>been any effort to make this a bit more extensible?
>
>I wrote a patch for JPython (since lost when I switched jobs) that allowed
>me to use a properties file to map a Java class to a Python wrapper.  This
>allowed me to wrap a Money object and to have it perform all the magic
>methods.
>
>I would be willingly to write the patch again since I would like some of
>this functionality but didn't want to work on something that perhaps
someone
>has already started.  If no one has started, are there any ideas floating
>around, such as adding it to the registry the way the modules are loaded by
>first looking at "python.modules.builtin".

I can't remember anyone asking for this. A feature request that
resembles the java2py wrappers are ProxyCollection creations.

  http://mail.python.org/pipermail/jpython-dev/2000-February/000022.html
  http://mail.python.org/pipermail/jpython-dev/2000-March/000023.html

A possible problem with most such class->handler mappings are the lack
of inheritance support. F.ex subclasses of BigDecimal should, by
default, be handled by the same wrapper as BigDecimal.

In addition to registry support, there should also be support for adding
additinal wrapper (and proxy) classes through an python API.

>Finally, if we do add such functionality, should we have as the ant project
>does an optional jar which contains Python-wrapped Java objects, for
example
>PySession and PyRequest, that would be outside of the core?

Not sure. I think the additional wrappers will be outside the core by
definition. I don't believe that jython should search for a optional.jar
and include it if found. IMO that is better done by the author by
including her optional.jar on the classpath.

regards,
finn

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