RE: [Jython-users] Embedding Python in Java Applications?

[Vovan <vov...@ho...>]

Thanks for the explanation. I think I figured that one out. My code last
night looked similar to your: I anI =
(I)interp.eval("C.C()").__tojava__(I.class); - though I must say this is
even cleaner-looking. It's just that I've been using the Python C API for
some time, and I expected that it would work similarly here, which it
doesn't, but that's okay. :)

Thanks,
Vovan

-----Original Message-----
From: Jeff Emanuel [mailto:JEm...@lg...] 
Sent: Tuesday, August 10, 2004 4:13 AM
To: Vovan
Subject: RE: [Jython-users] Embedding Python in Java Applications?

I didn't read your problem, just your code.  How about if your Python class
implements a Java interface?
 
I.java:
public interface I { public void f(); }
 
C.py:
import I
class C(I):
  def f(self):
    pass
 
Use it from Java like this:
 
PythonInterpreter interp=new PythonInterpreter();
interp.execfile("C.py");
I anI = (I)interp.eval("C.C()").__tojava__(I.class);
anI.f();
 
You can use some indirection to clean up the required syntax in the .py.
For example, perhaps you just want the user to define a function f.
 
F.py:
def f():
  pass
 
You could have a boiler-plate C.py:
 
import I
class C2(I):
  def __init__(self,aCallable):
    self.otherF=aCallable
  def f(self):
    self.otherF()
 
Then in java:
 
PythonInterpreter interp=new PythonInterpreter();
// Do this once.
interp.execfile("C.py");
// Do this for each F.
interp.execfile("F.py");
I anI = (I)interp.eval("C.C2(f)").__tojava__(I.class);
anI.f();
 
 
 
 

 
________________________________

From: Vovan [mailto:vov...@ho...]
Sent: Mon 8/9/2004 11:38 AM
To: Jeff Emanuel
Cc: jyt...@li...
Subject: RE: [Jython-users] Embedding Python in Java Applications?



So there is no way to get the class wrapped automatically in a nice little
object, and I'd have to write a wrapper class myself, which would go through
a global interpreter instance?

 

Vovan

 

________________________________

From: jyt...@li...
[mailto:jyt...@li...] On Behalf Of Jeff Emanuel
Sent: Monday, August 09, 2004 10:23 AM
To: Vovan
Cc: jyt...@li...
Subject: RE: [Jython-users] Embedding Python in Java Applications?

 

I would do it like this:

 

PythonInterpreter interp=new PythonInterpreter();

interp.exec("import pythontest");

interp.exec("pythontest.testfunc()");

 

	-----Original Message-----
	From: Vovan [mailto:vov...@ho...] 
	Sent: Friday, August 06, 2004 10:14 AM
	To: jyt...@li...
	Subject: [Jython-users] Embedding Python in Java Applications?

	Hi,

	 

	This might be a silly question - never used Jython before - but how
would I go about using Python modules in a Java application?

	 

	Well, this warrants a little more explanation. :)

	 

	So, I am toying around with a simple MUD server. Now, my idea was to
use a scripting language to define behaviours of different items, so that I
can update those behaviours, and even add new ones, all without ever
stopping the server - which is written in Java.

	 

	Now, I don't know what's the best way to do it - any hints about
this are certainly welcome, too :) - but my solution was that I would
basically have an Item class, and then I would have a bunch of Python
subclasses of item, all overriding a function which gets invoked when the
user wants to use the item. But the problem I am having is - I am not sure
how to actually now use the Python class? The Java code can detect when the
user wants to use the item, but I am not sure how to actually invoke the
Python function?

	 

	I looked around the net, and found this resource here:

	 

	http://www.samspublishing.com/articles/article.asp?p=26127&seqNum=6

	 

	And that says that I need to call __builtin__.__import__, and give
it the name of the module I want to import... But it always returns null...
I wrote a simple test program to try it out. Basically, the structure is
like this:

	 

	d Project

	|

	+-JythonTest.java

	|

	+-pythontest.py

	|
	+-__init__.py

	 

	pythontest.py simply contains some functions I could call to see if
the module got loaded. And then, inside the Java file, I have:

	 

	import org.python.core.*;

	import org.python.util.*;

	 

	public class JythonTest {

	  public static final void main(String[] agrs) {

	            //Before we can import stuff, we need to initialize the
interpreter:

	            PythonInterpreter.initialize(System.getProperties(),

	
null,

	
new String[0]);

	 

	//Right so first we would like to import the test module...

	            PyModule testModule = (PyModule)
__builtin__.__import__("pythontest");

	 

	            if (testModule == null) {

	              throw new NullPointerException("Object returned by
__builtin__.__import__ is null...");

	            }

	 

	            //Next, let's try and call the testfunc:

	            testModule.invoke("testfunc");

	  }

	}

	 

	Well, what happens when I compile and run that, is that the null
pointer exception always gets thrown - the __import__ method returns null...

	 

	If anyone could tell me what I'm doing wrong here, I'd much obliged.
:)

	 

	TIA,

	Vovan