code: public static <X, P extends MessageQueryParameter<X>, R extends RequestBody, M extends MessageParameters> X getQueryParameter(
  			final HandlerRequest<R, M> request,
  			final Class<P> queryParameterClass) throws RestHandlerException {
  
  		return getQueryParameter(request, queryParameterClass, null);
  	}
docs: Returns the value of a query parameter, or {@code null} if the query parameter is not set.
  @throws RestHandlerException If the query parameter is repeated.