Third-party libraries cannot access META-INF/filename resources

[AndreiJuan <An...@gmail.com>]

Some third-party libraries rely on files placed under META-INF in "the
classpath" for configuration -- Jersey and Hibernate, for example.  However,
"the classpath" in an OSGi context does not exist any more in its "classic"
(pre-OSGi) acceptance.

With Jersey, copying the files under my own bundle proved to be a usable
workaround and Jersey manages to load those files properly.  However,
Hibernate (more exactly, org.hibernate.ejb.Ejb3Configuration) follows a
different strategy: it asks the current thread's context classloader what
the URL to the resource is, then it attempts to read from that URL itself.

Although I'm setting the current thread's context class loader to be my
bundle's classloader (in a static block at the top of my bundle activator),
Ejb3Configuration fails to read that file when running in Felix, because the
URL returned by the classloader is something like "bundle://...", which it
does not know how to process.

Is there a "Felix-recommended" (or perhaps better, OSGi-recommended) way of
placing those "META-INF" resources?  (I cannot wait until all third-party
bundles become OSGi-friendly, sorry.)

The only thing I could think of was to set the current thread's context
class loader not directly to my bundle's (Felix) class loader, but to a
custom one that I write, and that for a certain (configurable) set of
resources it returns "file://..." URLs to a custom directory within the
container, and for everything else it defers to the Felix class loader.

Any better idea would be appreciated.



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Re: Third-party libraries cannot access META-INF/filename resources

[Stuart McCulloch <mc...@gmail.com>]

2009/5/8 AndreiJuan <An...@gmail.com>

>
> Some third-party libraries rely on files placed under META-INF in "the
> classpath" for configuration -- Jersey and Hibernate, for example.
>  However,
> "the classpath" in an OSGi context does not exist any more in its "classic"
> (pre-OSGi) acceptance.
>
> With Jersey, copying the files under my own bundle proved to be a usable
> workaround and Jersey manages to load those files properly.  However,
> Hibernate (more exactly, org.hibernate.ejb.Ejb3Configuration) follows a
> different strategy: it asks the current thread's context classloader what
> the URL to the resource is, then it attempts to read from that URL itself.
>
> Although I'm setting the current thread's context class loader to be my
> bundle's classloader (in a static block at the top of my bundle activator),
> Ejb3Configuration fails to read that file when running in Felix, because
> the
> URL returned by the classloader is something like "bundle://...", which it
> does not know how to process.
>
> Is there a "Felix-recommended" (or perhaps better, OSGi-recommended) way of
> placing those "META-INF" resources?  (I cannot wait until all third-party
> bundles become OSGi-friendly, sorry.)
>
> The only thing I could think of was to set the current thread's context
> class loader not directly to my bundle's (Felix) class loader, but to a
> custom one that I write, and that for a certain (configurable) set of
> resources it returns "file://..." URLs to a custom directory within the
> container, and for everything else it defers to the Felix class loader.
>
> Any better idea would be appreciated.
>

you might want to look into using the "extender" pattern:

   http://www.osgi.org/blog/2007/06/osgi-and-hibernate.html

basically have one bundle that watches for other bundles - it scans
their META-INF contents and programmatically registers them with
the hibernate bundle

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> View this message in context:
> http://www.nabble.com/Third-party-libraries-cannot-access-META-INF-filename-resources-tp23431881p23431881.html
> Sent from the Apache Felix - Users mailing list archive at Nabble.com.
>

-- 
Cheers, Stuart