public VisitorResponse getNext() {
        throw new UnsupportedOperationException("This datahandler doesn't support polling");
    }
Returns the next response of this session. This method returns
immediately.

@return the next response, or null if no response is ready at this time
@throws UnsupportedOperationException if data handler does not support
                                      the operation
documentapi/src/main/java/com/yahoo/documentapi/VisitorDataHandler.java