protected String resolveRelativeDirectoryPathString(File resourcesDir, String directoryName, String stack, String service) {
    File dir = resolveDirectory(directoryName, stack, service);
    if (dir != null) {
      return dir.getPath().substring(resourcesDir.getPath().length() + 1);
    }
    return null;
  }
@param directoryName
@param stack
@param service
@return the relative path of the directory if it exists and is not empty
ambari-server/src/main/java/org/apache/ambari/server/stack/ServiceDirectory.java