title: JBoss EAP 6.3 / Castor 1.0 - MappingException: Could not find the class
body: <p>When moving a formerly WebSphere Java EE application to JBoss EAP 6.3, a runtime exception was thrown when invoking the marshall(Object) method of Castor 1.0's org.exolab.castor.xml.Marshaller object:</p>
  
  <p><code>org.exolab.castor.mapping.MappingException: Nested error: org.exolab.castor.mapping.MappingException: Could not find the class
  {fully qualified Java class name}</code></p>
  
  <p>(The Marshaller is trying to serialize an object to XML.)</p>
  
  <p>I see no obvious class path issues. There is seemingly no reason why this application, which compiles fine using JBoss Developer Studio, would fail at runtime.</p>
  
  <p>The problem occurs with the first Java class described in the mapping.xml file -- not with the class that I'm trying to serialize, unless by coincidence it happens to be the first class in the mapping.xml file.</p>
  
  <p>What might be the problem, and what is a solution?</p>