running jython bytecode using java

Question

It looks like I'm missing something.

When using Jython to run my Python code in Java, Java bytecode files are generated (test.py -> [email protected]).

Can I run these classes directly using java?

In other words, I want to make this:

$ java test@py [additional cp args]

work.

The intent: writing Python code and not having to give away source code.

Answer 1

Here's what works for me:

test_p.py:

def foo():
  print 'test from Python'

TestJ.java:

import org.python.core.PyFrame;
import org.python.core.PyFunctionTable;
import org.python.util.PythonInterpreter;

public class TestJ
{
  public static void main(String[] args)
  {
    final PythonInterpreter interpreter = new PythonInterpreter();

    interpreter.exec("import sys");

    try
      {
        final Class<?> clazz = Class.forName("test_p$py");

        final java.lang.reflect.Constructor constructor
          = clazz.getConstructor(String.class);

        final PyFunctionTable module = (PyFunctionTable)constructor.newInstance("");

        final java.lang.reflect.Method method
          = clazz.getDeclaredMethod("foo$1",
                                    PyFrame.class,
                                    org.python.core.ThreadState.class);

        method.invoke(module,
                      (PyFrame)interpreter.eval("sys._getframe()").__tojava__(PyFrame.class),
                      org.python.core.Py.getThreadState());
      }
    catch (final ClassNotFoundException e)
      { e.printStackTrace(); }
    catch (final NoSuchMethodException e)
      { e.printStackTrace(); }
    catch (final InstantiationException e)
      { e.printStackTrace(); }
    catch (final IllegalAccessException e)
      { e.printStackTrace(); }
    catch (final java.lang.reflect.InvocationTargetException e)
      { e.printStackTrace(); }
  }
}

Compile test_p.py into test_p$py.class:

$JYTHON_HOME/jython $JYTHON_HOME/Lib/compileall.py .

Move test_p.py out of the way, to prove it's not being used:

mkdir hidden
mv test_p.py hidden/

Compile:

javac -cp $JYTHON_HOME/jython.jar TestJ.java

Test:

java -cp $JYTHON_HOME/jython.jar:. TestJ

Output:

test from Python

Answer 2

See FAQ - Embedding Jython.

Note that jythonc is no longer supported:

jythonc doesn't handle generators and is difficult to debug and improve. The current thinking is to add capabilites to jython itself to generate bytecode from py files and run those statically compiled items rather than jythonc's approach of making Java classes that work like the base Python code. The current thinking runs as follows:

• Turn Python classes into Java classes without a Java interface or class using function annotations to specify the static Java type information
• statically compile proxy classes for Python classes that extend Java classes
• remove code from core that is only there to support jythonc

The example suggests special annotation for any method in a Python class that needs to be visible from Java:

class Simple(object):
  @java
  def __init__(self):

  @java(String, String)
  def firstWord(self, param):
    return param.split(' ')[0]