I made a little progress on this issue. Looks like the endorsed mechanism has been replaced with jigsaw / modules. Not 100% certain of this and would be grateful if somebody could confirm my suspicion.

So I tried to create a custom module and declare a dependency in my application

Added jboss-deployment-structure.xml to the META-INF folder of my EAR

<?xml version="1.0" encoding="UTF-8"?>

<jboss-deployment-structure>

  <ear-subdeployments-isolated>true</ear-subdeployments-isolated>

  <deployment>

    <dependencies>

      <module name="com.abc.additional" export="true"/>

      <module name="com.abc.dependencies" export="true" />

    </dependencies>

  </deployment>

</jboss-deployment-structure>

And added a new module folder and descriptor

<?xml version="1.0" encoding="UTF-8"?>

<module xmlns="urn:jboss:module:1.1" name="com.thunderhead.additional">

    <resources>

      <resource-root path="ABC-serializer-2.7.0.jar"/>

      <resource-root path="ABC-xalan-2.7.0.jar"/>

      <resource-root path="resolver.jar"/>

  </resources>

</module>

This didn't help resolve the issue. Any suggestion on how to specify / override the default XML libraries for either a single application EAR or the entire JBoss installation.

This looks a little better, however now I am getting : NoClassDefFoundError: javax/naming/InitialContext. I already posted about this issue on a separate thread as a different part of the application is also running in to the same issue. Any idea where this class is. I can't find it in any of the modules or jar files.