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Date: Thu, 8 Nov 2012 10:45:42 +0100
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Subject: Re: java.lang.LinkageError for javax.xml.stream.XMLStreamReader
From: Rupert Westenthaler <rupert.westenthaler@gmail.com>
To: dev@stanbol.apache.org
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Hi Suat,

My experience is regarding the Java XML stuff it that there are two
possibilities that do work

(1) to embed everything in your bundle and exclude those packages from
the imported
(2) to import everything and embed nothing

You should avoid

* exporting XML stuff
* use XML stuff in your interfaces (as this would require to export things)

With the change from Solr 3.2 to 3.6.1 I decided to switch from (2) to
(1) and because of that there are now bundles (from the ServiceMix
project) that provide some of the XML libraries. The XML api, Xerxes
and Xalan is anyway provided by the JDK. Because of that option (1)
should be now fine for most of cases.

The error you encounter seams to be related to two different instances
of "javax/xml/stream/XMLStreamReader" Class loaded from different
Classloaders. AFAIK this class is part of the Java XML apis so one
guess is that your Bundle Classpath does include its own version for
the Java XML apis. If this is the case you should get rid of the
embedded dependency.

An other possibility is that the bootloader instance is initialised by
using the ContextClassloader and those is a different one as the
BundleClassloader. If this is the case you need to replace the context
classloader with the bundle classloader (you can find examples in the
o.a.stanbol.commons.solr.core module as it needs to do the same when
instantiating Solr components).

> As far as I see both "Apache ServiceMix :: Specs :: Stax API 1.0" bundle
> and our "frameworkfragment" injects the javax.xml.stream package into
> the OSGi environment.

Even that this is not the cause for your problem this is indeed an
issue. AFAIK bundles that export packages should also import them,
because then it does not interfere with packages exported by the
system bundle (as it is the case because of the Stanbol
frameworkfragment).

best
Rupert

--=20
| Rupert Westenthaler             rupert.westenthaler@gmail.com
| Bodenlehenstra=C3=9Fe 11                             ++43-699-11108907
| A-5500 Bischofshofen