code: public static String getBestRelativeURI(HttpServletRequest httpServletRequest) {
  
          String requestURI = httpServletRequest.getRequestURI();
          if (null == requestURI) return null;
  
          // "/petclinic" -> 10
          int bestBaseURILength = httpServletRequest.getContextPath().length();
  
          String servletPath = httpServletRequest.getServletPath();
          if (null != servletPath) {
  
              String pathInfo = httpServletRequest.getPathInfo();
  
              if (null != pathInfo && !pathInfo.isEmpty()) {
                  bestBaseURILength += servletPath.length(); // like "/petclinic/servlet" -> 18
                  if (servletPath.endsWith("/")) bestBaseURILength--; // like "/petclinic/servlet/" -> 18
              } else {
                  ServletContext servletContext = httpServletRequest.getServletContext();
                  for (String mapping : ServletRegistrationUtil.getServletMappings(servletContext)) {
                      if (mapping.equals(servletPath) || (mapping.endsWith("/*") && mapping.substring(0, mapping.length() - 2).equals(servletPath))) {
                          bestBaseURILength += servletPath.length(); // like "/petclinic/servlet" -> 18
                          if (servletPath.endsWith("/")) bestBaseURILength--; // like "/petclinic/servlet/" -> 18
                          break;
                      }
                  }
              }
  
          }
  
          return requestURI.substring(bestBaseURILength);
      }
docs: 12.2 Specification of Mappings In the Web application deployment descriptor, the following syntax is used to define mappings:
  A string beginning with a ‘/’ character and ending with a ‘/*’ suffix is used for path mapping.
  A string beginning with a ‘*.’ prefix is used as an extension mapping.
  The empty string ("") is a special URL pattern that exactly maps to the application's context root, i.e., requests of the form  http://host:port/<contextroot>/. In this case the path info is ’/’ and the servlet path and context path is empty string (““).
  A string containing only the ’/’ character indicates the "default" servlet of the application. In this case the servlet path is the request URI minus the context path and the path info is null.
  All other strings are used for exact matches only
  @param httpServletRequest
  @return