WebServiceContext#getUserPrincipal() returns null in JBossWS Metro stack when the user is authenticated

I am using JBossWS metro stack to implement Username Token profile authentication for a web service. The authentication will be triggered, and the credential information in SOAP header can be obtained in a custom realm authenticator.

However, even if the authentication pass and the service operation is performed, the WebServiceContext#getUserPrincipal() always returns null.

I attached a simple maven 2 project (for service implementation) and a SOAP request (sent with SOAP UI), you can use that to reproduce this issue.