Why can't JAXB find my jaxb.index when running inside Apache Felix?

OK, this took quite some digging, but the answer is not that surprising and not even that complicated:

JAXB can't find jaxb.index, because by default, newInstance(String) uses the current thread's class loader (as returned by Thread.getContextClassLoader()). This doesn't work inside Felix, because the OSGi bundles and the framework's threads have separate class loaders.

The solution is to get a suitable class loader from somewhere and use newInstance(String, ClassLoader). I got a suitable class loader from one of the classes in the package that contains jaxb.index, a sensible choice for flexibility reasons probably is ObjectFactory:

ClassLoader cl = my.package.name.ObjectFactory.class.getClassLoader();
JAXBContext jc = JAXBContext.newInstance("my.package.name", cl);

Maybe you could also get at the class loader that the Bundle instance is using, but I couldn't figure out how, and the above solution seems safe to me.

I faced similar issue with the project I am working on. After reading http://jaxb.java.net/faq/index.html#classloader I realized that JAXBContext is not able to find the package containing jaxb.index.

I will try to make this as clear as possible.

We have

Bundle A
   -- com.a
      A.java
        aMethod()
        {
            B.bMethod("com.c.C");
        }
MANIFEST.MF
Import-Package: com.b, com.c         

Bundle B
   -- com.b
      B.java
        bmethod(String className)
        {
            Class clazz = Class.forName(className);
        }

Export-Package: com.b

Bundle C
   -- com.c
      C.java
        c()
        {
            System.out.println("hello i am C");
        }

Export-Package: com.c

To relate to JAXB. class B is JAXBContext and bMethod is newInstance()

If you are familiar with OSGi package restrictions then it must be very clear now that Bundle B is not Importing package com.c i.e class C is not visible to class B hence it cannot instantiate C.

The solution would be to pass a ClassLoader to bMethod. This ClassLoader should come from a bundle that is importing com.c. In this case we can pass A.class.getClassLoader() since bundle A is importing com.c

Hope this was helpful.