Hi Marc

This looks very familiar. We've had a couple of projects with CXF integration. 
Basically, the uber-bundle they are providing introduces classloading issues 
beyond repair. We've got it to work for a customer by modifying the manifest of 
the uber bundle. But eventually, we had to upgrade to a more recent CXF version 
and had to re-do everything. Bottom line, the total cost of ownership was too 
high.

I'd suggest the following solutions (in order of preference):

1.) Don't use CXF at runtime. Instead, use the jax-* support shipped with the 
JDK. For this, modify the sling.properties to expose the relevant packages via 
the system class loader, as mentioned here: 
https://helpx.adobe.com/experience-manager/using/creating-cq-bundles-consume-web.html
 / 
https://helpx.adobe.com/experience-manager/using/creating-cxf-bundles-consume-web.html

2.) Wrap your application along with the CXF uber-bundle in an application 
Subsystem to isolate it (see OSGi enterprise spec: 
https://osgi.org/download/r5/osgi.enterprise-5.0.0.pdf).

Good luck!
- Olaf


-----Original Message-----
From: marc.schle...@sdv-it.de [mailto:marc.schle...@sdv-it.de]
Sent: Donnerstag, 11. Februar 2016 11:26
To: users@felix.apache.org
Subject: Classloading issue for XML with Apache CXF in Felix

Hello everyone

I have set up a test-environment for several frontend-bundles (struts,
jsf) which use our internal webservices via Apache CXF. The basic configuration 
is working and simple webservice-calls are running fine.
However, when I am accessing some other services CXF is running into 
classloading-errors. I guess that the webservice is returning some 
error-response which CXF cannot handle.

Caused by: java.lang.RuntimeException: XPathFactory#newInstance() failed to 
create an XPathFactory for the default object model:
http://java.sun.com/jaxp/xpath/dom with the
XPathFactoryConfigurationException:
javax.xml.xpath.XPathFactoryConfigurationException: No XPathFactory 
implementation found for the object model:
http://java.sun.com/jaxp/xpath/dom

After some research I found out that a lot of imports in the CXF bundles are 
actually optional which is why I am running into runtime-classloader-problems. 
After some more research, I found out that CXF needs Saxon as well as Xerces 
and Xalan...and here the real trouble starts.

Servicemix is providing the required libraries as a bundle, so I add those 
org.apache.servicemix.bundles.saxon (9.7.0.1_1) 
org.apache.servicemix.bundles.xerces (2.11.0.1) 
org.apache.servicemix.bundles.xalan (2.7.2.2)

This also resolves fine in BndTools, so time for another round

Failed to start bundle org.apache.servicemix.bundles.xalan-2.7.2.2,
exception Unable to resolve org.apache.servicemix.bundles.xalan [53](R
53.0): missing requirement [org.apache.servicemix.bundles.xalan [53](R 53.0)] 
osgi.wiring.package; (osgi.wiring.package=org.w3c.dom.traversal)
Unresolved requirements: [[org.apache.servicemix.bundles.xalan [53](R 53.0)] 
osgi.wiring.package; (osgi.wiring.package=org.w3c.dom.traversal)]

A lot of the xml-apis have been moved to the JDK, but not all. So I've added
org.apache.servicemix.specs.jaxp-api-1.4 (2.5.0)

And now I am doomed :-)
At first, it seemed Felix is not booting because nothing happened, but when I 
set felix.log.level=4 I can see endless repetition of this

----------------------------------------------------
DEBUG: Candidate permutation failed due to a conflict between imports; will try 
another if possible. (Uses constraint violation. Unable to resolve resource 
org.ops4j.pax.web.pax-web-jsp [org.ops4j.pax.web.pax-web-jsp [77](R 77.0)] 
because it is exposed to package 'org.w3c.dom' from resources 
org.apache.felix.framework [org.apache.felix.framework [0](R 0)] and
org.apache.servicemix.specs.jaxp-api-1.4
[org.apache.servicemix.specs.jaxp-api-1.4 [56](R 56.0)] via two dependency 
chains.

Chain 1:
  org.ops4j.pax.web.pax-web-jsp [org.ops4j.pax.web.pax-web-jsp [77](R 77.0)]
    import: (osgi.wiring.package=org.w3c.dom)
     |
    export: osgi.wiring.package: org.w3c.dom
  org.apache.felix.framework [org.apache.felix.framework [0](R 0)]

Chain 2:
  org.ops4j.pax.web.pax-web-jsp [org.ops4j.pax.web.pax-web-jsp [77](R 77.0)]
    import: (osgi.wiring.package=org.w3c.dom.traversal)
     |
    export: osgi.wiring.package: org.w3c.dom.traversal; uses:=org.w3c.dom
    export: osgi.wiring.package=org.w3c.dom
  org.apache.servicemix.specs.jaxp-api-1.4
[org.apache.servicemix.specs.jaxp-api-1.4 [56](R 56.0)])
----------------------------------------------------

There are other packages as well, but this should be enough to make the point. 
Despite that Felix seems not to be able to recover from this, Felix is right: 
because the SystemBundle exports the JDK packages [1] which are also included 
in org.apache.servicemix.specs.jaxp-api-1.4 it doesnt know what to do.

The problem is that due to its xml-history [2], the JDK is not providing all 
classes or packages CXF needs to work. Despite the missing 
org.w3c.dom.traversal package, other packages do not inlcude all classes (for 
example org.w3c.dom.ElementTraversal which is also accessed at some point by 
CXF).

Is there any way I can tell Felix which packages it should not export, so I can 
use org.apache.servicemix.specs.jaxp-api-1.4? Or what bundles do I need to get 
full xml-processing within OSGI/Felix for CXF?

I have tried setting "org.osgi.framework.system.packages" to the list provided 
by [1] without the offending packages from jaxp but then the framework 
complains about tons of other problems.

Any help is really appreciated because I am running out of ideas.

regards
Marc

[1]
https://github.com/apache/felix/blob/trunk/framework/src/main/resources/default.properties
(in my case section jre-1.8 )
[2]
http://stackoverflow.com/questions/11677572/dealing-with-xerces-hell-in-java-maven

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