public ConnectionFactory(){
        _connectionConfig = ConnectionConfig.getInstance();
        switch(Integer.parseInt(_connectionConfig.getProperty(ConnectionConfig.DRIVER))){
            case 1 :  this._iConnection = new PostgreSqlConnection(_connectionConfig.getProperty(ConnectionConfig.HOST),
                                                                   _connectionConfig.getProperty(ConnectionConfig.PORT),
                                                                   _connectionConfig.getProperty(ConnectionConfig.DATABASE),
                                                                   _connectionConfig.getProperty(ConnectionConfig.USER),
                                                                   _connectionConfig.getProperty(ConnectionConfig.PASSWD),
                                                                   DriverList.PostgreSQL.getDriverName());
                break;
            case 2 : this._iConnection = new OracleConnection(_connectionConfig.getProperty(ConnectionConfig.HOST),
                                                                   _connectionConfig.getProperty(ConnectionConfig.PORT),
                                                                   _connectionConfig.getProperty(ConnectionConfig.DATABASE),
                                                                   _connectionConfig.getProperty(ConnectionConfig.USER),
                                                                   _connectionConfig.getProperty(ConnectionConfig.PASSWD),
                                                                   DriverList.Oracle.getDriverName());
                break;
            case 3 : this._iConnection = new SqlServerConnection(_connectionConfig.getProperty(ConnectionConfig.HOST),
                                                                   _connectionConfig.getProperty(ConnectionConfig.PORT),
                                                                   _connectionConfig.getProperty(ConnectionConfig.DATABASE),
                                                                   _connectionConfig.getProperty(ConnectionConfig.USER),
                                                                   _connectionConfig.getProperty(ConnectionConfig.PASSWD),
                                                                   DriverList.SQLServer.getDriverName());
                break;
            case 4 : this._iConnection = new MySqlConnection(_connectionConfig.getProperty(ConnectionConfig.HOST),
                                                                   _connectionConfig.getProperty(ConnectionConfig.PORT),
                                                                   _connectionConfig.getProperty(ConnectionConfig.DATABASE),
                                                                   _connectionConfig.getProperty(ConnectionConfig.USER),
                                                                   _connectionConfig.getProperty(ConnectionConfig.PASSWD),
                                                                   DriverList.MySQL.getDriverName());
                break;
            default:
                break;
        }        
    }