Passing OSGi bundles for Jython Interpreter on-the-fly

Question

we would like to integrate the Jython interpreter into our Eclipse RCP based solution and we need to access the OSGi bundles (e.g. everything from Activator.getContext().getBundles() ) from there.

How could I pass these bundles to a Jython PythonInterpreter object python.path property, so I can import these classes from the Jython code?

(I get similar error messages when I try to import packages e.g.: from org.eclipse.chemclipse.msd.converter.chromatogram import ChromatogramConverterMSD)

ImportError: cannot import name ChromatogramConverterMSD

Answer 1

I managed to find a solution after working on this issue for days.

First we need a ClassLoader which can load OSGi bundles if necessary:

public class JythonClassLoader extends ClassLoader {

private final Bundle bundle;

public JythonClassLoader(ClassLoader parent, Bundle bundle) {
    super(parent);
    this.bundle = bundle;
}

@Override
protected Class<?> findClass(String name) throws ClassNotFoundException {

    // System.out.println("findClass " + name);
    try {
        return super.findClass(name);
    } catch(ClassNotFoundException e) {
        Class<?> loadClass = bundle.loadClass(name);
        if(loadClass != null)
            return loadClass;
        throw e;
    }
}}

Then the PythonInterpreter needs to know about this ClassLoader. The best is to set up the environment for the PythonInterpreter before. The following class does the job:

public class JythonEnvironment {

private final Bundle bundle;

public JythonEnvironment(Bundle bundle) {
    this.bundle = bundle;
}

public PySystemState getPySystemState() {

    Properties properties = new Properties();
    String jythonPath = net.openchrom.thirdpartylibraries.jython.Activator.getJythonPath();
    properties.setProperty("python.home", jythonPath);
    properties.setProperty("python.cachedir.skip", "true");
    Properties systemProperties = System.getProperties();
    PySystemState.initialize(systemProperties, properties, new String[]{""});
    PySystemState pySystemState = new PySystemState();
    JythonClassLoader classLoader = new JythonClassLoader(getClass().getClassLoader(), bundle);
    pySystemState.setClassLoader(classLoader);
    return pySystemState;
}

public PythonInterpreter getInterpreter() {

    return new PythonInterpreter(null, getPySystemState());
}

public PythonInterpreter getInterpreter(OutputStream outStream, OutputStream errStream) {

    PythonInterpreter interpreter = new PythonInterpreter(null, getPySystemState());
    interpreter.setErr(outStream);
    interpreter.setOut(errStream);
    return interpreter;
}}

The JythonEnvironment class needs to know about the bundle. The best if that one can be received through the Activator.

JythonEnvironment environment = new JythonEnvironment(Activator.getDefault().getBundle());

Hope this answer will save time, if someone else needs to integrate Jython into an Eclipse RCP based solution.