code: @Override
      public List<String> getAvailableTargetIds() {
          String[] availableTargetIds = SiteProperties.getAvailableTargetIds();
          if (ArrayUtils.isNotEmpty(availableTargetIds)) {
              return Arrays.asList(availableTargetIds);
          } else {
              throw new IllegalStateException("No available target IDs specified in the configuration");
          }
      }
docs: Returns the available target IDs defined in the current site configuration. If not defined, and
  {@link IllegalStateException} is thrown.