public void invoke(MessageContext msgContext)
            throws AxisFault

Invoke is called to do the actual work of the Handler object. If there is a fault during the processing of this method it is invoke's job to catch the exception and undo any partial work that has been completed. Once we leave 'invoke' if a fault is thrown, this classes 'onFault' method will be called. Invoke should rethrow any exceptions it catches, wrapped in an AxisFault.