Question

我已经编写了一个DB单例类来提供单个数据库连接，我接受另一个类中的连接如果它是null我必须为null检查条件请解释告诉我最佳做法

class TransferToBigQuery(GoogleCloudStorageToBigQueryOperator): 
    """Class to transfer data from Google cloud storage to Big Query""" 
    def __init__( 
        self, id, bucket, destination_project_dataset_table, source_objects=None, 
        schema_fields=None, schema_object=None, source_format='CSV', 
        create_disposition='CREATE_IF_NEEDED', 
        skip_leading_rows=0, write_disposition='WRITE_EMPTY', 
        field_delimiter=',', max_id_key=None, file_xcom=None, 
        bigquery_conn_id='bigquery_default', 
        google_cloud_storage_conn_id='google_cloud_storage_default', 
        delegate_to=None, schema_update_options=(), *args, **kwargs): 
        super(GoogleCloudStorageToBigQueryOperator, self).__init__(*args, 
                                                               **kwargs)

另一个班级

public class DBSingleton {
    private static final DBSingleton ONLY_ONE = new DBSingleton();
    private Connection connection = null;
    private DBSingleton() {
        try {
            Class.forName("com.mysql.jdbc.Driver");
            connection = DriverManager.getConnection("url", "username","pwd");// SQLException
        } catch (ClassNotFoundException | SQLException e) {
            e.printStackTrace();
        }
    }

    public static DBSingleton getInstance() {
        return ONLY_ONE;
    }

    public Connection getcon() {
        return connection;
    }
}

Answer 1

你可以尝试

public class BDConnection {
private static final Logger LOGGER = LoggerFactory.getLogger(BDConnection.class);
private static Connection connection = null;

public static Connection getConnection() {
    if(connection == null){
        createConnection();
    }
    return connection;
}

private static void createConnection() {
    try {
        Class.forName(ImportExportFilesUtils.getResourceMessage("driver.name")).newInstance();
        connection = DriverManager.getConnection(ImportExportFilesUtils.getResourceMessage("database.test.url"), ImportExportFilesUtils.getResourceMessage("database.test.username"),
                ImportExportFilesUtils.getResourceMessage("database.test.password"));
    } catch (Exception ex) {
        LOGGER.error("Cannot load the driver for ojdbc", ex);
    }
}

public static void closeConnection() {
    if (connection != null) {
        try {
            connection.close();
        } catch (SQLException e) {
            LOGGER.error("Cannot close the connection with the database", e);
        }
    }
}

}

空单检查DB单例

1 个答案: