code: protected void initExtractors() {
          Parameter[] parameters = controllerMethod.getParameters();
          extractors = new MethodParameterExtractor[parameters.length];
          for (int i = 0; i < parameters.length; i++) {
              MethodParameter parameter = new MethodParameter(controllerMethod, i);
              MethodParameterExtractor extractor = application.getExtractors().stream()
                  .filter(e -> e.isApplicable(parameter))
                  .findFirst()
                  .orElse(null);
  
              if (extractor == null) {
                  throw new PippoRuntimeException(
                      "Method '{}' parameter {} of type '{}' does not specify a extractor",
                      LangUtils.toString(controllerMethod), i + 1, parameter.getParameterType());
              }
  
              extractors[i] = extractor;
          }
      }
docs: Init extractors from controller method.