Using Guice with OSGi

Question

I have a project that I am trying to convert to OSGi. However, this project has been built with Guice as its dependency injection manager. It's a large project with Guice interwoven all throughout. Guice has been giving me many fits with the conversion process. Specifically, it has been given me a NoClassDefFoundError for com.google.inject.internal.cglib.reflect.FastClass. I have made sure that nothing is package-private and I also downloaded and used the guice-2.0-customloader.jar. Still, to no avail.

Is there any advice from anyone that has gone down this path? It is worth mentioning that I use peaberry to get dynamic services from the OSGi environment (for a plugin-type architecture) that I then use in the program later on.

Thanks a lot, Steve

Answer 1

I'm assuming your comments on package-private are related to this page on Guice and bridging class loaders?

There's a bug report/patch that may be related to your issue: http://code.google.com/p/google-guice/issues/detail?id=343

Have you tried adding Guice and cglib to the standard classpath and doing boot delegation for them? That would prove/disprove your issue is the same one as mentioned on the above bug report.

Answer 2

Hard to say exactly what the problem is, classloader issues can be very situation specific in OSGi and hard to debug.

If guice really is a core to your application it may make sense to make it a Fragment bundle of the System Bundle. The System Bundle is the root node in the classloader tree for ALL bundles. If classes exist in this bundle, they'll be accessible everywhere. This is a technique I've used successfully to wrap Swing LAF (Substance, Alloy, Jide) as OSGi bundles. They've gotta be at the root level since all of my bundles use Swing (especially the Swing classloader)

You'll want to check the OSGi specs for creating a Fragment bundle and making that fragment bundle a framework extension fragment. I've only been able to do this using Eclipse's Equinox runtime. At the time I wrote most of the supporting classes, Apache Felix did not yet support framework extension fragments. It may have changed now. I have no idea about frameworks (knopplefish, spring-dm)

Answer 3

Just use Peaberry. It has all the support you need for using Guice in OSGi. No need to reinvent everything from scratch!

Answer 4

You could try my latest patch for Issue 343 - just attached a freshly patched build which is the latest Guice trunk plus this one patch, so people can try it and give feedback.

The latest patch avoids a lot of these CGLIB exceptions without forcing you to make classes public, and also provides a better error message in the few remaining places where this is still necessary (basically when you explicitly use method interception).