jython-users

[<jgo...@co...>]

Jeff and I have been discussing this off-list; I figured I'd send the
discussion back to the list.

-- John

----- Forwarded message from John Goerzen <jgo...@co...> -----

X-Addr-Extension: sent-mail
To: Jeff Emanuel <je...@ad...>
Subject: Re: [Jython-users] tojava() failing
From: John Goerzen <jgo...@co...>

OK.  I did:

System.out.println(this.getClass().getClassLoader().getClass().getName());
System.out.println(newobj.getClass().getClassLoader().getClass().getName());

Resulting in:

com.lutris.classloader.MultiClassLoader
org.python.core.BytecodeLoader1

MultiClassLoader is a subclass of java.lang.ClassLoader adding in
functionality such as loading classes from URLs, ZIPs, etc.  (This is
an Enhydra servlet).

Interestingly, this is JDK 2 but it's using Jython's JDK 1
BytecodeLoader.

Let me show you exactly what I'm trying to do:

In Java:    (before adding the printlns and other debug stuff)

        PythonInterpreter interp = new PythonInterpreter();
        interp.exec("mod = __import__('" + brob + "')");
        interp.exec("cl = mod." + brob + "()");
        Object newobj = interp.get("cl", Object.class);
        return (ListBO) newobj;

In this case, 'brob' is ListBOFoo, and it's loading this Python code:

from quovix.business.util import *

class ListBOFoo(ListBO):
    def getDescription(self):
        desc = ListBO.getDescription(self) # Superclass call
        return "Foo_" + desc

Very simple stuff.  I have it working with jythonc but I'm trying to
eliminate jythonc from the picture so it can be loaded 100%
dynamically.

Thanks for your assistance!

-- John


Jeff Emanuel <je...@ad...> writes:

> The java class Class has a method to return its ClassLoader.
> You can do something like this:
> 
>    System.out.println(this.getClass().getClassLoader());
>    System.out.println(newobj.getClass().getClassLoader());
> 
> If they are different, the classes are in effect not equal.
> I'm not sure why that would be or how to work around it.  I've
> done things as you are trying and it worked.  If we know
> what the classloaders are, perhaps we can discover why they
> are different, or what action to take.
> 
> You can also try newobj.getClass().isAssignableFrom(this.getClass())
> 
> That is likely to be false since you know you can't do the cast.
> 
> 
> 
> John Goerzen wrote:
> 
> > Jeff Emanuel <je...@ad...> writes:
> >
> 
> >>It is likely that your ListBO class was loaded by two different class
> >>loaders.  Try printing out the classloaders for your Java this instance
> >>and your newobj.  Even if the classes are the same, if they were loaded
> >>by different loaders, then they really aren't equal.
> >>
> > OK this is unfamiliar territory for me.  I don't know what a class
> 
> > loader is or how to print it.  If the loaders are different, how would
> > I go about resolving the problem?  One is the regular static stuff
> > loaded as usual with classes generated by javac; the other, Python.
> > Ideas?
> > Thanks!
> 
> > -- John
> 
> >
> 
> 
> 

-- 
John Goerzen <jgo...@co...>    GPG: 0x8A1D9A1F    www.complete.org

----- End forwarded message -----