code: public static String getUrl(SlingHttpServletRequest request, String url,
                                  String selectors, String extension) {
          LinkMapper mapper = (LinkMapper) request.getAttribute(LinkMapper.LINK_MAPPER_REQUEST_ATTRIBUTE);
          return getUrl(request, url, selectors, extension, mapper != null ? mapper : LinkMapper.RESOLVER);
      }
docs: Builds a mapped link to the path (resource path) with optional selectors and extension.
  
  @param request   the request context for path mapping (the result is always mapped)
  @param url       the URL to use (complete) or the path to an addressed resource (without any extension)
  @param selectors an optional selector string with all necessary selectors (can be 'null')
  @param extension an optional extension (can be 'null' for extension determination)
  @return the mapped url for the referenced resource