Eclipse PDE/OSGi: Reflections Library not finding packages

Question

The org.reflections library does not function correctly when it's used inside an Eclipse Plugin project.

For instance, the following code should return all classes of a given subtype in a given package:

Reflections reflections = new Reflections("my.package");
Set<Class<? extends Subtype>> classes = reflections.getSubTypesOf(Subtype.class);

When running the project as a Plugin, classes will be empty. Inserting a main() and running it as a normal Java application will correctly return the expected classes.

I've tried to:

Include the Reflections library as a normal third-party jar dependency

Include the Reflections library as an OSGi bundle (http://stackoverflow.com/questions/8339845/reflections-library-not-working-when-used-in-an-eclipse-plug-in)

Edit: current process (based on stackoverflow answer above):

1) New Plugin-Project (OSGIReflections called) based on external JARs (Reflections and Javassist)

2) In my actual Plugin-project (X) I add a dependency on OSGIReflections in Dependencies -> Required Plug-ins

2.a) If I run the project as normal java app: Reflections is working

2.b) If I run the project as plugin project: Reflections is not working

3) Create the BundleUrlType class

4) How do I activate this BundleUrlType? In my plugin Activator I call the createReflections(context.getBundle()) function but I do not have a .data file. How do I generate that?

The second link to [Include the Reflections library as an OSGi bundle](http://stackoverflow.com/questions/8339845/reflections-library-not-working-when-used-in-an-eclipse-plug-in) looks pretty good. Try following those instructions. If they don't work, give details of what went wrong. — Neil Bartlett, Jul 21 '16 at 00:08
@NeilBartlett This is my process: 1) New Plugin-Project (OSGIReflections called) based on external JARs (Reflections and Javassist) 2) In my actual Plugin-project (X) I add a dependency on OSGIReflections in Dependencies -> Required Plug-ins 2.a) If I run the project as normal java app: Reflections is working 2.b) If I run the project as plugin project: Reflections is not working 3) Create the BundleUrlType class 4) How do I activate this BundleUrlType? In my plugin Activator I call the createReflections(context.getBundle()) function but I do not have a .data file. How do I generate that? — memoryStream, Jul 21 '16 at 12:09
I don't know what a `.data` file is. It's not needed for OSGi, is it something required by the Reflections library? If so, check the docs for Reflections. — Neil Bartlett, Jul 21 '16 at 16:02
Oh I see, `reflectiveplugin.data` is not a file, it's a package name. I think it's where the author of that SO answer put his sample classes. — Neil Bartlett, Jul 21 '16 at 16:06
have you tried using "Eclipse-RegisterBuddy: bundle-symbolic-name" header? — Hisham Khalil, Jul 22 '16 at 11:02

score 0 · Answer 1 · edited Apr 10 '23 at 05:54

I know that's pretty old question, but for all struggling with OSGi with probably all suggestions on SO not working I have small tip:

My case: Reflections 0.9.8 (later versions should work similar) on a Fabric8 container.

TL;DR: The key was make org.osgi.framework.Bundle to work as java.lang.ClassLoader and passed to Reflections instance.

During debugging sessions I've found that org.reflections.util.ClasspathHelper finds two ClassLoaders by default as a result of:

Thread.currentThread().getContextClassLoader();

containing only org.osgi.* and org.apache.karaf.* packages
Reflections.class.getClassLoader();

containing org.reflections.* package

so there is no place with user created code. I've found that both ClassLoader and Bundle have two common methods:

    Class<?> loadClass(String var1) throws ClassNotFoundException;

    Enumeration<URL> getResources(String var1) throws IOException;

so I've created ClassLoader with delegation to Bundle:

public class BundleClassLoader extends ClassLoader {

    private final Bundle bundle;

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

    @Override
    public Enumeration<URL> getResources(String name) throws IOException {
        return bundle.getResources(name);
    }

    @Override
    public Class<?> loadClass(String name) throws ClassNotFoundException {
        return bundle.loadClass(name);
    }

}

and passed it to Reflections instance:

new Reflections(packageName, new BundleClassLoader(bundleContext.getBundle()), new SubTypesScanner(false));

edit: As I found out later, I still needed own implementation of UrlType that matches OSGi implementation. In my case, despite of using fixed version of Reflections (mvn:org.apache.servicemix.bundles/org.apache.servicemix.bundles.reflections/0.9.8_1 which has its own bundle protocol implementation) I needed to add implementation based on example in answer from similar thread changing BUNDLE_PROTOCOL from bundleresource to bundle.

Eclipse PDE/OSGi: Reflections Library not finding packages

1 Answers1