Flink-1.9流计算开发：三、flatMap函数

public class StreamTest {
    private static final Logger LOG = LoggerFactory.getLogger(StreamTest.class);
    public static void main(String[] args) throws Exception {
        final StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
        String[] words = {"apple","orange","banana","watermelon"};
        //创建DataSource
        //根据给定的元素创建一个数据流，元素必须是相同的类型，比如全部为String，或者全部为int。
        DataStreamSource<String> ds = env.fromElements(words);
        //Transformations
        //对DataStream应用一个flatMap转换。对DataStream中的每一个元素都会调用FlatMapFunction接口的具体实现类。flatMap方法可以返回任意个元素，当然也可以什么都不返回。
        SingleOutputStreamOperator<String> flatMap = ds.flatMap(new FlatMapFunction<String, String>() {
            @Override
            public void flatMap(String value, Collector<String> out) throws Exception {
                out.collect(value);
                out.collect(value.toUpperCase());
            }
        });
        //sinks打印出信息
        //给DataStream添加一个Sinks
        flatMap.addSink(new SinkFunction<String>() {
            @Override
            public void invoke(String value) throws Exception {
                LOG.info(value);
            }
        });

        env.execute("Flink Streaming Java API Skeleton");
    }
}

15:44:46,305 INFO  fun.cosmozhu.session3.StreamTest                              - watermelon
15:44:46,305 INFO  fun.cosmozhu.session3.StreamTest                              - apple
15:44:46,305 INFO  fun.cosmozhu.session3.StreamTest                              - WATERMELON
15:44:46,305 INFO  fun.cosmozhu.session3.StreamTest                              - banana
15:44:46,305 INFO  fun.cosmozhu.session3.StreamTest                              - BANANA
15:44:46,305 INFO  fun.cosmozhu.session3.StreamTest                              - orange
15:44:46,305 INFO  fun.cosmozhu.session3.StreamTest                              - ORANGE
15:44:46,305 INFO  fun.cosmozhu.session3.StreamTest                              - APPLE

https://github.com/chaoxxx/learn-flink-stream-api/blob/master/src/main/java/fun/cosmozhu/session3/StreamTest.java