flink MySql TwoPhaseCommitSink样例

以下是一个使用 Flink 的 `TwoPhaseCommitSinkFunction` 将数据写入 MySQL 数据库的样例代码：

public class MySqlTwoPhaseCommitSink extends TwoPhaseCommitSinkFunction<MyData, Connection, Void> {

    private final String username;
    private final String password;
    private final String drivername;
    private final String dburl;

    public MySqlTwoPhaseCommitSink(String username, String password, String drivername, String dburl) {
        this.username = username;
        this.password = password;
        this.drivername = drivername;
        this.dburl = dburl;
    }

    @Override
    public void invoke(TransactionContext transactionContext, MyData myData, Context context) throws Exception {
        // do nothing in invoke, wait for the prepareTransaction method
    }

    @Override
    public void prepareTransaction(TransactionContext transactionContext) throws Exception {
        // create a new connection
        Connection connection = DriverManager.getConnection(dburl, username, password);
        // set the connection to the transaction context
        transactionContext.setTransactionConnection(connection);
    }

    @Override
    public void commitTransaction(TransactionContext transactionContext) throws Exception {
        // get the connection from the transaction context
        Connection connection = transactionContext.getTransactionConnection();
        // commit the transaction
        connection.commit();
        // close the connection
        connection.close();
    }

    @Override
    public void abortTransaction(TransactionContext transactionContext) throws Exception {
        // get the connection from the transaction context
        Connection connection = transactionContext.getTransactionConnection();
        // rollback the transaction
        connection.rollback();
        // close the connection
        connection.close();
    }

    @Override
    public TypeInformation<Void> getProducedType() {
        // return void as the produced type
        return TypeInformation.of(Void.class);
    }

    @Override
    protected void finalize() throws Throwable {
        // close the connection if it hasn't been closed yet
        DriverManager.getConnection(dburl, username, password).close();
    }
}

在上面的代码中，`MyData` 是需要写入 MySQL 数据库的数据类型。在 `invoke` 方法中，我们不做任何操作，只是等待 `prepareTransaction` 方法。在 `prepareTransaction` 方法中，我们创建一个新的 MySQL 数据库连接并将其设置到事务上下文中。在 `commitTransaction` 和 `abortTransaction` 方法中，我们获取事务上下文中的连接并提交或回滚事务，然后关闭连接。在 `getProducedType` 方法中，我们返回 `void` 类型作为生产类型。在 `finalize` 方法中，我们确保关闭连接。

使用上面的代码，我们可以使用以下方式将数据写入 MySQL 数据库：

StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();

DataStream<MyData> dataStream = ... // get the data stream

MySqlTwoPhaseCommitSink sink = new MySqlTwoPhaseCommitSink(username, password, drivername, dburl);

TwoPhaseCommitSinkFunctionWrapper<MyData, Void> sinkWrapper =
    TwoPhaseCommitSinkFunctionWrapper.newBuilder(sink).build();

dataStream.addSink(sinkWrapper);

env.execute();

在上面的代码中，我们创建了一个 `MySqlTwoPhaseCommitSink` 对象，并使用 `TwoPhaseCommitSinkFunctionWrapper` 将其包装在内。然后，我们将数据流添加到这个包装器中，并执行任务。