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From: Olaf Otto <olaf.otto@unic.com>
To: "users@felix.apache.org" <users@felix.apache.org>
Subject: RE: Classloading issue for XML with Apache CXF in Felix
Thread-Topic: Classloading issue for XML with Apache CXF in Felix
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Date: Thu, 11 Feb 2016 12:02:23 +0000
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Hi Marc

This looks very familiar. We've had a couple of projects with CXF integrati=
on. Basically, the uber-bundle they are providing introduces classloading i=
ssues beyond repair. We've got it to work for a customer by modifying the m=
anifest of the uber bundle. But eventually, we had to upgrade to a more rec=
ent 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 t=
he JDK. For this, modify the sling.properties to expose the relevant packag=
es via the system class loader, as mentioned here: https://helpx.adobe.com/=
experience-manager/using/creating-cq-bundles-consume-web.html / https://hel=
px.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/downloa=
d/r5/osgi.enterprise-5.0.0.pdf).

Good luck!
- Olaf


-----Original Message-----
From: marc.schlegel@sdv-it.de [mailto:marc.schlegel@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 configura=
tion is working and simple webservice-calls are running fine.
However, when I am accessing some other services CXF is running into classl=
oading-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 impleme=
ntation 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 ar=
e actually optional which is why I am running into runtime-classloader-prob=
lems. 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.bundl=
es.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=3Dorg.w3c.dom.traversal)
Unresolved requirements: [[org.apache.servicemix.bundles.xalan [53](R 53.0)=
] osgi.wiring.package; (osgi.wiring.package=3Dorg.w3c.dom.traversal)]

A lot of the xml-apis have been moved to the JDK, but not all. So I've adde=
d
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=3D4 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 res=
ource org.ops4j.pax.web.pax-web-jsp [org.ops4j.pax.web.pax-web-jsp [77](R 7=
7.0)] because it is exposed to package 'org.w3c.dom' from resources org.apa=
che.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=3Dorg.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=3Dorg.w3c.dom.traversal)
     |
    export: osgi.wiring.package: org.w3c.dom.traversal; uses:=3Dorg.w3c.dom
    export: osgi.wiring.package=3Dorg.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 poi=
nt. 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 t=
o do.

The problem is that due to its xml-history [2], the JDK is not providing al=
l classes or packages CXF needs to work. Despite the missing org.w3c.dom.tr=
aversal 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 nee=
d to get full xml-processing within OSGI/Felix for CXF?

I have tried setting "org.osgi.framework.system.packages" to the list provi=
ded 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/def=
ault.properties
(in my case section jre-1.8 )
[2]
http://stackoverflow.com/questions/11677572/dealing-with-xerces-hell-in-jav=
a-maven

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