@RequiresSession
  public AlertHistoryEntity findById(long alertId) {
    return m_entityManagerProvider.get().find(AlertHistoryEntity.class, alertId);
  }
Gets an alert with the specified ID.

@param alertId
         the ID of the alert to retrieve.
@return the alert or {@code null} if none exists.
ambari-server/src/main/java/org/apache/ambari/server/orm/dao/AlertsDAO.java