code: protected Map<String, Object> preProcess(final String target, final Request baseRequest, final HttpServletRequest request,
  	        final HttpServletResponse response) throws IOException, ServletException {
  		return Collections.emptyMap();
  	}
docs: Validate the request and extract any data from the HTTP request that will be required to process the request asynchronously.
  
  If the request is invalid, then handle the request appropriately.
  
  *** NOTE: to indicate that this method handled the request, set Request.handled to true: <code>baseRequest.setHandled(true);</code>
  
  @param target
  @param baseRequest
  @param request
  @param response
  @return