code: public String getServletPath(HttpServerRequest<I> request, HttpKeyEvaluationContext context) {
          String requestUriPath = context.getRequestUriPath(request);
          if (null != requestUriPath) {
              return matcher.getServletPath(requestUriPath);
          }
          return "";
      }
docs: This must be called if and only if {@link #apply(HttpServerRequest, HttpKeyEvaluationContext)}
  returned for the same request.
  
  @param request Request which satisfies this key.
  @param context The key evaluation context.
  
  @return The servlet path.