public static synchronized void deserialize() throws DatabaseException {
    for (String user : UserNodeKeywordsDAO.findUsers()) {
      Map<String, UserNodeKeywords> udkMap = new HashMap<String, UserNodeKeywords>();

      for (UserNodeKeywords udk : UserNodeKeywordsDAO.findByUser(user)) {
        udkMap.put(udk.getNode(), udk);
      }

      userNodeKeywordsMgr.put(user, udkMap);
    }
  }
  public static synchronized void serialize() throws DatabaseException {
    UserNodeKeywordsDAO.clean();

    for (String user : userNodeKeywordsMgr.keySet()) {
      log.info("User: {}", user);

      for (UserNodeKeywords udk : userNodeKeywordsMgr.get(user).values()) {
        log.info("Document: {}", udk);
        UserNodeKeywordsDAO.create(udk);
      }
    }
  }