code: protected String[] getCacheDomains(Method method) {
          if (null == method.getData().get(Domain.CACHE_DOMAIN_KEY)) {
              return null;
          }
  
          JSONValue jsonValue = JSONParser.parseStrict(method.getData().get(Domain.CACHE_DOMAIN_KEY));
          if (null == jsonValue) {
              return null;
          }
  
          JSONArray jsonArray = jsonValue.isArray();
          if (null != jsonArray) {
              String[] dd = new String[jsonArray.size()];
              for (int i = 0; i < jsonArray.size(); ++i) {
                  dd[i] = jsonArray.get(i).isString().stringValue();
              }
  
              return dd;
          }
          return null;
      }
docs: when using the {@link Domain} annotation on services, we are able to group responses
  of a service to invalidate them later on more fine grained. this method resolves a
  possible ``domain`` to allow grouping.
  
  @return array of names of cache domains