code: private Set<String> validateURL(ValidationHelper helper, Context context, String url) {
          String pathToCheck = url;
          Set<String> serverVariables = new HashSet<String>();
  
          while (pathToCheck.contains("{")) {
              if (!pathToCheck.contains("}")) {
                  final String message = Tr.formatMessage(tc, "serverInvalidURL", pathToCheck);
                  helper.addValidationEvent(new ValidationEvent(ValidationEvent.Severity.ERROR, context.getLocation("url"), message));
                  return serverVariables;
              }
              int firstIndex = pathToCheck.indexOf("{");
              int lastIndex = pathToCheck.indexOf("}");
  
              if (firstIndex > lastIndex) {
                  final String message = Tr.formatMessage(tc, "serverInvalidURL", pathToCheck);
                  helper.addValidationEvent(new ValidationEvent(ValidationEvent.Severity.ERROR, context.getLocation("url"), message));
                  return serverVariables;
              }
  
              String variable = pathToCheck.substring(firstIndex + 1, lastIndex);
  
              if (variable.isEmpty() || variable.contains("{") || variable.contains("/")) {
                  final String message = Tr.formatMessage(tc, "serverInvalidURL", pathToCheck);
                  helper.addValidationEvent(new ValidationEvent(ValidationEvent.Severity.ERROR, context.getLocation("url"), message));
                  return serverVariables;
              }
  
              serverVariables.add(variable);
              pathToCheck = pathToCheck.substring(lastIndex + 1);
          }
  
          if (pathToCheck.contains("}")) {
              final String message = Tr.formatMessage(tc, "serverInvalidURL", pathToCheck);
              helper.addValidationEvent(new ValidationEvent(ValidationEvent.Severity.ERROR, context.getLocation("url"), message));
              return serverVariables;
          }
  
          return serverVariables;
      }
docs: Validate the url and extract server variables parameters