@Override
  public int size(final DatabaseTable table) throws DatabaseException {
    preOperationCheck();

    final StringBuilder sb = new StringBuilder();
    sb.append("SELECT COUNT(" + KEY_COLUMN + ") FROM ").append(table.toString());

    PreparedStatement statement = null;
    ResultSet resultSet = null;
    try {
      statement = connection.prepareStatement(sb.toString());
      resultSet = statement.executeQuery();
      if (resultSet.next()) {
        return resultSet.getInt(1);
      }
    } catch (SQLException e) {
      final ErrorInformation errorInformation =
          new ErrorInformation(
              PwmError.ERROR_DB_UNAVAILABLE, "size operation failed: " + e.getMessage());
      lastError = errorInformation;
      throw new DatabaseException(errorInformation);
    } finally {
      close(statement);
      close(resultSet);
    }

    updateStats(true, false);
    return 0;
  }
 private void getNextItem() {
   try {
     if (resultSet.next()) {
       nextValue = resultSet.getString(KEY_COLUMN);
     } else {
       close();
     }
   } catch (SQLException e) {
     finished = true;
     LOGGER.warn("unexpected error during result set iteration: " + e.getMessage());
   }
   updateStats(true, false);
 }
  private boolean isValid(final Connection connection) {
    if (connection == null) {
      return false;
    }

    if (status != PwmService.STATUS.OPEN) {
      return false;
    }

    try {
      final Method getFreeSpaceMethod = File.class.getMethod("isValid");
      final Object rawResult = getFreeSpaceMethod.invoke(connection, 10);
      return (Boolean) rawResult;
    } catch (NoSuchMethodException e) {
      /* no error, pre java 1.6 doesn't have this method */
    } catch (Exception e) {
      LOGGER.debug(
          "error checking for isValid for " + connection.toString() + ",: " + e.getMessage());
    }

    final StringBuilder sb = new StringBuilder();
    sb.append("SELECT * FROM ")
        .append(DatabaseTable.PWM_META.toString())
        .append(" WHERE " + KEY_COLUMN + " = ?");
    PreparedStatement statement = null;
    ResultSet resultSet = null;
    try {
      statement = connection.prepareStatement(sb.toString());
      statement.setString(1, KEY_ENGINE_START_PREFIX + instanceID);
      statement.setMaxRows(1);
      resultSet = statement.executeQuery();
      if (resultSet.next()) {
        resultSet.getString(VALUE_COLUMN);
      }
    } catch (SQLException e) {
      final ErrorInformation errorInformation =
          new ErrorInformation(
              PwmError.ERROR_DB_UNAVAILABLE, "isValid operation failed: " + e.getMessage());
      lastError = errorInformation;
      LOGGER.error(errorInformation.toDebugStr());
      return false;
    } finally {
      close(statement);
      close(resultSet);
    }
    return true;
  }
 private static void close(final ResultSet resultSet) {
   if (resultSet != null) {
     try {
       resultSet.close();
     } catch (SQLException e) {
       LOGGER.error("unexpected error during close resultSet object " + e.getMessage(), e);
     }
   }
 }
  @Override
  public String get(final DatabaseTable table, final String key) throws DatabaseException {
    if (traceLogging) {
      LOGGER.trace("attempting get operation for table=" + table + ", key=" + key);
    }
    preOperationCheck();
    final StringBuilder sb = new StringBuilder();
    sb.append("SELECT * FROM ").append(table.toString()).append(" WHERE " + KEY_COLUMN + " = ?");

    PreparedStatement statement = null;
    ResultSet resultSet = null;
    String returnValue = null;
    try {
      statement = connection.prepareStatement(sb.toString());
      statement.setString(1, key);
      statement.setMaxRows(1);
      resultSet = statement.executeQuery();

      if (resultSet.next()) {
        returnValue = resultSet.getString(VALUE_COLUMN);
      }
    } catch (SQLException e) {
      final ErrorInformation errorInformation =
          new ErrorInformation(
              PwmError.ERROR_DB_UNAVAILABLE, "get operation failed: " + e.getMessage());
      lastError = errorInformation;
      throw new DatabaseException(errorInformation);
    } finally {
      close(statement);
      close(resultSet);
    }

    if (traceLogging) {
      final LinkedHashMap<String, Object> debugOutput = new LinkedHashMap<>();
      debugOutput.put("table", table);
      debugOutput.put("key", key);
      debugOutput.put("result", returnValue);
      LOGGER.trace(
          "get operation result: " + JsonUtil.serializeMap(debugOutput, JsonUtil.Flag.PrettyPrint));
    }

    updateStats(true, false);
    return returnValue;
  }
 public void close() {
   if (resultSet != null) {
     try {
       resultSet.close();
     } catch (SQLException e) {
       LOGGER.error("error closing inner resultset in iterator: " + e.getMessage());
     }
   }
   finished = true;
 }