[Jython-dev] java->python problems

[dman <ds...@ri...>]

Hi all.  This probably isn't appropriate for the -dev list, but too
frequently I don't get a response on the -users list.

I'm trying to use Jython(c) to allow using Moshe Zadka's PMS framework
along with a Java/Swing GUI for a school project.  (The other group
members are writing the gui and they don't know python)  I've run into
a couple of problems, though, all related to java's type system.

There are several modules in the PMS package.  I have taken the base
classes of the inheritance tree and made them inherit from
java.lang.Object and added the @sig lines.  A simplified example :

----- PMS/AbstractFolder.py
class AbstractFolder( java.lang.Object ) : pass

----- PMS/Folder.py
import AbstractFolder
class Folder( AbstractFolder.AbstractFolder ) : pass


I also have the following class as a factory for the GUI to create a
hardcoded folder for the prototype demo.

----- DemoFolder1.py
class DemoFolder1( java.lang.Object ) :
    def make( self , name ) :
        """
        @sig public Object make( String name )
        """

        server = PMS.MaildirServer.MaildirServer( "server_name" , "." )
        PMS.Configuration.Configuration().servers[ server ] = lambda x : x
        folder = PMS.Folder.Folder( server , name )
        folder.create()

        print folder.__class__ # correctly prints "PMS.Folder.Folder"
        return folder



I used jythonc to compile the stuff, and everything compiles fine.
The Java code that uses this looks like :


            Object folder = (new DemoFolder1()).make( "Demo1" );
            MailMessage.Message message = new MailMessage.Message();

            // This line prints out
            // org.python.proxies.PMS.Folder$Folder$2
            System.out.println( folder.getClass() ) ;

            try
            {
                ((Folder)folder).save_message( message );
            }
            catch ( Exception err )
            {
                // I get a ClassCastException here
            }


Even though the Python factory returns an object that should match the
generated java class, it doesn't match and java can't handle it.


I also tried :
            Folder f = new Folder(
                new MaildirServer( "name" , "." ) , "Demo2" ) ;
            f.save_message( message ) ;

This works if I write it in Python, but written in Java gives :

    Exception occurred during event dispatching:
    Traceback (innermost last):
      (no code object) at line 0
    TypeError: __init__() takes at least 3 arguments (1 given)

As you can see, too much debugging info was lost in the translation to
java so I have no idea where this error is occurring.


I can think of 2 workarounds to the problem, but neither is very
desirable, so any suggestions, hints, pointers, or even wild guesses
are greatly appreciated.


As an additional annoyance, it seems that a jythonc-compiled python
module can't import any python modules that are not translated to
java.  Is this limitation real, or am I just doing something wrong?

TIA!
-D