code: @Override
      public void setUserName(String userName) throws JMSException {
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
              SibTr.entry(this, tc, "setUserName", userName);
          jcaManagedConnectionFactory.setUserName(userName);
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
              SibTr.exit(this, tc, "setUserName");
      }
docs: /*
  default user name is null.