private void closeConnection() {
   try {
     if (statement != null) statement.close();
     if (connection != null) {
       JDBCExceptionReporter.logWarnings(connection.getWarnings());
       connection.clearWarnings();
       connectionProvider.closeConnection(connection);
       connectionProvider.close();
     }
   } catch (Exception e) {
     System.err.println("Could not close connection");
     e.printStackTrace();
   }
 }