/**
   * Initialize the event queue.
   *
   * @param props A container of configuration properties.
   * @exception FrameworkException Thrown if configuration is invalid.
   */
  public void initialize(Map props) throws FrameworkException {
    String temp = (String) props.get(LOAD_EVENT_BATCH_SIZE_PROP);

    if (StringUtils.hasValue(temp)) {
      maxDatabaseEventLoadSize = StringUtils.getInteger(temp);

      if (Debug.isLevelEnabled(Debug.SYSTEM_CONFIG))
        Debug.log(
            Debug.SYSTEM_CONFIG,
            "QUEUE OPERATION: Initializing: Maximum-database-event-batch-load-size is ["
                + maxDatabaseEventLoadSize
                + "] rows.");
    }
  }
  /**
   * Reset any events meeting the given criteria so that they can be retried.
   *
   * @param criteria An event containing the event-selection criteria.
   * @return The number of events reset.
   * @exception FrameworkException Thrown on errors.
   */
  protected static int reset(Event criteria) throws FrameworkException {
    Debug.log(
        Debug.MSG_STATUS, "QUEUE OPERATION: Resetting events in database for database queue ...");

    if (!StringUtils.hasValue(criteria.channelName)) {
      throw new FrameworkException(
          "ERROR: Event channel name is a required queue search criteria.");
    }

    Connection dbConn = null;

    PreparedStatement ps = null;

    long startTime = -1;

    if (Debug.isLevelEnabled(Debug.BENCHMARK)) startTime = System.currentTimeMillis();

    try {
      dbConn = DBConnectionPool.getInstance().acquireConnection();

      if (Debug.isLevelEnabled(Debug.DB_DATA))
        Debug.log(
            Debug.DB_DATA, "Criteria used to reset events in database:\n" + criteria.describe());

      // If no identifier was given that uniquely identifies a single event ...
      if (criteria.id == 0) {
        // Use last error time and error count, if available.
        if (Debug.isLevelEnabled(Debug.DB_DATA))
          Debug.log(Debug.DB_DATA, "\n" + LINE + "\nExecuting SQL:\n" + UPDATE_EVENT_RETRY_SQL);

        ps = dbConn.prepareStatement(UPDATE_EVENT_RETRY_SQL);

        ps.setString(1, criteria.channelName);

        if (criteria.lastErrorTime == null) ps.setNull(2, Types.DATE);
        else ps.setTimestamp(2, criteria.lastErrorTime);

        if (criteria.errorCount < 1) ps.setNull(3, Types.INTEGER);
        else ps.setInt(3, criteria.errorCount);
      } else {
        // An Id was given which should uniquely identify a single event, so we should
        // skip using any other qualifying criteria, if present.
        if (Debug.isLevelEnabled(Debug.DB_DATA))
          Debug.log(
              Debug.DB_DATA, "\n" + LINE + "\nExecuting SQL:\n" + UPDATE_EVENT_RETRY_BY_ID_SQL);

        ps = dbConn.prepareStatement(UPDATE_EVENT_RETRY_BY_ID_SQL);

        ps.setString(1, criteria.channelName);

        ps.setInt(2, criteria.id);
      }

      int numRows = ps.executeUpdate();

      DBConnectionPool.getInstance().commit(dbConn);

      if (Debug.isLevelEnabled(Debug.DB_DATA))
        Debug.log(
            Debug.DB_DATA, "Committed SQL execution affected [" + numRows + "] rows.\n" + LINE);

      return numRows;
    } catch (SQLException sqle) {
      throw new DatabaseException(
          "ERROR: Could not execute SQL statement:\n" + DBInterface.getSQLErrorMessage(sqle));
    } catch (Exception e) {
      throw new DatabaseException("ERROR: Could not execute SQL statement:\n" + e.toString());
    } finally {
      releaseDatabaseResources(dbConn, ps);

      if (Debug.isLevelEnabled(Debug.BENCHMARK) && (startTime > 0)) {
        long stopTime = System.currentTimeMillis();

        Debug.log(
            Debug.BENCHMARK,
            "ELAPSED TIME ["
                + (stopTime - startTime)
                + "] msec:  "
                + "SQL: Time to reset event(s) in PersistentEvent database table.");
      }
    }
  }
  /**
   * Load any available events from the database up to the configured maximum.
   *
   * @param criteria An event containing the event-selection criteria.
   * @return The next available event on the queue.
   * @exception FrameworkException Thrown on errors.
   */
  private void loadFromDatabase(Event criteria) throws FrameworkException {
    Debug.log(Debug.MSG_STATUS, "QUEUE OPERATION: Loading events from database into queue ...");

    if (!StringUtils.hasValue(criteria.channelName)) {
      throw new FrameworkException(
          "ERROR: Event channel name is a required queue search criteria.");
    }

    Connection dbConn = null;

    PreparedStatement ps = null;

    long startTime = -1;

    if (Debug.isLevelEnabled(Debug.BENCHMARK)) startTime = System.currentTimeMillis();

    try {
      dbConn = DBConnectionPool.getInstance().acquireConnection();

      if (Debug.isLevelEnabled(Debug.DB_DATA))
        Debug.log(Debug.DB_DATA, "\n" + LINE + "\nExecuting SQL:\n" + QUERY_EVENT_SQL);

      if (Debug.isLevelEnabled(Debug.DB_DATA))
        Debug.log(
            Debug.DB_DATA, "Criteria used in query against database:\n" + criteria.describe());

      ps = dbConn.prepareStatement(QUERY_EVENT_SQL);

      ps.setString(1, criteria.channelName);

      ResultSet rs = ps.executeQuery();

      for (int counter = 0; (counter < maxDatabaseEventLoadSize) && rs.next(); counter++) {
        Event event = new Event();

        event.channelName = rs.getString(CHANNEL_NAME_COL);
        event.id = rs.getInt(ID_COL);

        event.message = DBLOBUtils.getCLOB(rs, MESSAGE_COL);

        if (Debug.isLevelEnabled(Debug.MSG_LIFECYCLE))
          Debug.log(Debug.MSG_LIFECYCLE, "Event contents:\n" + event.message);

        event.arrivalTime = rs.getTimestamp(ARRIVAL_TIME_COL);
        event.errorStatus = rs.getString(ERROR_STATUS_COL);
        event.errorCount = rs.getInt(ERROR_COUNT_COL);
        event.lastErrorMessage = rs.getString(LAST_ERROR_MESSAGE_COL);
        event.lastErrorTime = rs.getTimestamp(LAST_ERROR_TIME_COL);

        // Add item to in-memory buffer.
        if (Debug.isLevelEnabled(Debug.MSG_STATUS))
          Debug.log(
              Debug.MSG_STATUS,
              "Adding event [" + event.describe() + "] to in-memory queue buffer.");

        queue.add(event);

        if (Debug.isLevelEnabled(Debug.MSG_STATUS))
          Debug.log(Debug.MSG_STATUS, "In-memory queue buffer size [" + queue.size() + "].");
      }

      if (Debug.isLevelEnabled(Debug.DB_DATA)) Debug.log(Debug.DB_DATA, "\n" + LINE);
    } catch (SQLException sqle) {
      throw new DatabaseException(
          "ERROR: Could not execute SQL statement:\n" + DBInterface.getSQLErrorMessage(sqle));
    } catch (Exception e) {
      throw new DatabaseException("ERROR: Could not execute SQL statement:\n" + e.toString());
    } finally {
      releaseDatabaseResources(dbConn, ps);

      if (Debug.isLevelEnabled(Debug.BENCHMARK) && (startTime > 0)) {
        long stopTime = System.currentTimeMillis();

        Debug.log(
            Debug.BENCHMARK,
            "ELAPSED TIME ["
                + (stopTime - startTime)
                + "] msec:  "
                + "SQL: Time to load event(s) from PersistentEvent database table.");
      }
    }
  }