5 Replies Latest reply on Feb 29, 2016 4:53 PM by kdolan1

Class loading problems with library version different from Wildfly version - help!

kdolan1 Jan 28, 2016 2:39 PM

I suspect we should be able to do what we want to do but obviously we are missing something. Any and all help to uncover what that may be or point us in a direction to look is greatly appreciated.

We want to use Xalan 2.7.2, not the version provided by Wildfly.
We put Xalan in our EAR and modified jboss-deployment-structure.xml to exclude the org.apache.xalan and org.apache.xerces modules (even though we shouldn't need to given documented class loading rules)
We wrote some code to confirm certain Xalan classes are loaded from our copy of Xalan - all is well, until....
We hit code that involves XPath classes (e.g., XPathImpl, XPathFactory) resulting in exceptions. Using the same confirmation technique, we confirmed these classes are loaded from the Wildfly Xalan module and must not be compatible with those loaded from other JARs.
If we modify the Wildfly Xalan JAR by removing "javax.xml.xpath.XPathFactory" from META-INF\services, our problems go away. Our code confirms the XPath classes are now loaded from the JRE. Not sure why the JRE. We would expect them to come from Xalan in our EAR.

What we don't want to do because we suspect it is the wrong thing to do is

Modify the Wildfly Xalan JAR as described above.
Replace the Wildfly Xalan JAR w/ Apache's version of 2.7.2.

Any ideas? What are we missing? Are our assumptions correct? We're pretty much at a standstill.

Many thanks in advance,

Kelly

1. Re: Class loading problems with library version different from Wildfly version - help!

ctomc Jan 28, 2016 2:51 PM (in response to kdolan1)

jdk version? WildFly version?
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2. Re: Class loading problems with library version different from Wildfly version - help!

kdolan1 Jan 28, 2016 2:53 PM (in response to ctomc)

Sorry, I should have included that.

Java 8. Wildfly 9.0.2 Final
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3. Re: Class loading problems with library version different from Wildfly version - help!

jaikiran Jan 28, 2016 10:54 PM (in response to kdolan1)

Can you post the entire exception stacktrace, the output of:

jar -tf yourear.ear

and if possible attach the application which reproduces this? The snippet of the code from your application, which triggers this will help too.
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4. Re: Class loading problems with library version different from Wildfly version - help!

kdolan1 Jan 29, 2016 5:04 PM (in response to jaikiran)
Thanks for the request. Unfortunately, it is impossible to attach our application due to its size but I tried creating a Sample App to demonstrate the problem. Please find it attached. Deploy it and enter "http://localhost:8080/SampleWar" in a browser window.

With the Sample App, I could not get exceptions thrown like we're seeing in our application. But the output shows that org.apache.xml classes are loaded from the Xalan/Xerces JARs in the WAR's lib folder but the XPath classes are loaded from the JRE rt.jar. The XPath classes also seem to be in the Xalan/Xerces JARs (specifically xml-apis.jar) in our WAR's lib folder as well and that is where I think we need them to come from in our application's environment to ensure compatibility. Puzzling... If I can get the Sample App to throw an exception I'll update it here.

jar -tf SampleEar.ear produces:
META-INF/
META-INF/jboss-deployment-structure.xml
SampleWar.war/
SampleWar.war/index.jsp
SampleWar.war/WEB-INF/
SampleWar.war/WEB-INF/lib/
SampleWar.war/WEB-INF/lib/serializer-2.7.2.jar
SampleWar.war/WEB-INF/lib/xalan-2.7.2.jar
SampleWar.war/WEB-INF/lib/xercesImpl-2.11.0.jar
SampleWar.war/WEB-INF/lib/xml-apis.jar

I'm working on getting the output of "jar -tf" from our application if I'm able to post it.

Thanks,
Kelly

SampleEar.ear 4.4 MB
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5. Re: Class loading problems with library version different from Wildfly version - help!

kdolan1 Feb 29, 2016 4:53 PM (in response to kdolan1)

We finally figured out our problem. The root cause was a copy of the Xalan 2.6 classes combined into an application JAR. We removed these classes and no longer had issues.

Thanks everyone.
Kelly
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