《从 0 到 1 学习 Flink》—— Data Sink 介绍

@PublicEvolving
public class PrintSinkFunction<IN> extends RichSinkFunction<IN> {
	private static final long serialVersionUID = 1L;
	private static final boolean STD_OUT = false;
	private static final boolean STD_ERR = true;
	private boolean target;
	private transient PrintStream stream;
	private transient String prefix;
	/**
	 * Instantiates a print sink function that prints to standard out.
	 */
	public PrintSinkFunction() {}
	/**
	 * Instantiates a print sink function that prints to standard out.
	 *
	 * @param stdErr True, if the format should print to standard error instead of standard out.
	 */
	public PrintSinkFunction(boolean stdErr) {
		target = stdErr;
	}
	public void setTargetToStandardOut() {
		target = STD_OUT;
	}
	public void setTargetToStandardErr() {
		target = STD_ERR;
	}
	@Override
	public void open(Configuration parameters) throws Exception {
		super.open(parameters);
		StreamingRuntimeContext context = (StreamingRuntimeContext) getRuntimeContext();
		// get the target stream
		stream = target == STD_OUT ? System.out : System.err;
		// set the prefix if we have a >1 parallelism
		prefix = (context.getNumberOfParallelSubtasks() > 1) ?
				((context.getIndexOfThisSubtask() + 1) + "> ") : null;
	}
	@Override
	public void invoke(IN record) {
		if (prefix != null) {
			stream.println(prefix + record.toString());
		}
		else {
			stream.println(record.toString());
		}
	}
	@Override
	public void close() {
		this.stream = null;
		this.prefix = null;
	}
	@Override
	public String toString() {
		return "Print to " + (target == STD_OUT ? "System.out" : "System.err");
	}
}

SingleOutputStreamOperator.addSink(new PrintSinkFunction<>();