jython-users

[Jython-users] newInstance() on a python created java class

[Edward P. <epo...@te...>]

Hello all.

I am trying to create and use objects created in Jython from java.
...
interp.exec("class PyJavaTestClass(JavaTestClass): pass");
interp.exec("ptc=PyJavaTestClass()");
...
JavaTestClass jtc = (JavaTestClass)interp.get("ptc",JavaTestClass.class);

jtc.something();    // ok
jtc = jtc.getClass().newInstance();    // error

I get:
Traceback (innermost last):
  (no code object) at line 0
ImportError: no module named main

Is it possible at all to do this? I am trying to integrate python created
object in a java plugin framework. In hava using forName() and newInstance()
was easy. Not sure I can even do the above.

I can think of an alternative way to do this, but that would mean
reimplementing my java plugin stuff too. Any hints on how to fix the above?

Thanks
-Ed

Re: [Jython-users] newInstance() on a python created java class

[Samuele P. <pe...@in...>]

This works:

import org.python.core.*;
import org.python.util.*;

public class Test {
    public static void main(String[] argv) {
      try {
        
        PySystemState.initialize();
        // PythonInterpreter interp = new PythonInterpreter();

        // add new 'classes' module to sys.modules
        PyModule classes = imp.addModule("classes"); 

        String defCode = "from java.lang import Object\n" +
                         "class C(Object): pass";

        // same as: exec defCode in classes.__dict__
        Py.exec(new PyString(defCode),classes.__dict__,null);

        Class cl = (Class)classes.__findattr__("C").__tojava__(Class.class);

        System.out.println(cl);

        Object c = cl.newInstance();

        System.out.println(c);

      } catch(Exception e) {
        e.printStackTrace();
      }

    }      
}

The point is that the Python class inheriting from Java
should be defined in a module that is present in sys.modules
or that can be imported (because Jython retrieves
the Python class corresponding to a Java side proxy class
by module/name),
that means also 'import' the code with the definition
would work, and other approaches using more or less
Java-side vs Python-side code and for example
the 'new' module.

The 'main' module in which a PythonInterpreter
executes code is not put in sys.modules, also
because there would be a conflict with multiple intepreters.

regards.