The xerces jar is removed from WFLY now, and the JAXP implementation from JDK 11+ is the default one. When the xerces is packaged in the user's deployment , the JDK's JAXP FactoryFinder will always load the service provider and implementation from the user provided xerces jar as the impl class defined by the service provider is org.apache.xerces.jaxp.DocumentBuilderFactoryImpl and this implementation will always be loaded first instead of the jdk's internal jaxp class com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderFactoryImpl.
We should provide some classloader to load the JDK's jaxp implementation for the webservice runtime ,and only used the packaged xerces from user's deployment when invoke the webservice implementation.