Flink DataStream API

public interface FlatMapFunction<T, O> extends Function, Serializable {
    void flatMap(T value, Collector<O> out) throws Exception;
}

public interface Function extends java.io.Serializable {}

@Public
public interface RichFunction extends Function {
    void open(Configuration parameters) throws Exception;
    
    void close() throws Exception;

    RuntimeContext getRuntimeContext();
    
    IterationRuntimeContext getIterationRuntimeContext();
    
    void setRuntimeContext(RuntimeContext t);
}

public class WordCount {

    public static void main(String[] args) throws Exception {
        // 步骤1
        StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
        // 步骤2
        DataStreamSource<String> source = env.fromElements(WORDS);
        // 步骤3
        source.flatMap(new Tokenizer()).keyBy(new KeySelector<Tuple2<String, Integer>, Object>() {

            @Override
            public Object getKey(Tuple2<String, Integer> value) throws Exception {
                return value.f0;
            }
        }).sum(1).addSink(new SinkFunction<Tuple2<String, Integer>>() {
            @Override
            public void invoke(Tuple2<String, Integer> value, Context context) throws Exception {
                System.out.println("单词：" + value.f0 + "，数量:" + value.f1);
            }
        });
        // 步骤4
        env.execute("WordCount Stream");
    }

    private static class Tokenizer extends RichFlatMapFunction<String, Tuple2<String, Integer>> {

        @Override
        public void flatMap(String value, Collector<Tuple2<String, Integer>> out) {
            String[] tokens = value.toLowerCase().split("\\W+");
            for (String token : tokens) {
                if (token.length() > 0) {
                    out.collect(new Tuple2<>(token, 1));
                }
            }
        }
    }

    public static final String[] WORDS =
            new String[] {
                    "To be, or not to be,--that is the question:--",
                    "Whether 'tis nobler in the mind to suffer",
                    "The slings and arrows of outrageous fortune",
                    "Or to take arms against a sea of troubles,",
                    "And by opposing end them?--To die,--to sleep,--",
                    "No more; and by a sleep to say we end",
                    "The heartache, and the thousand natural shocks",
                    "That flesh is heir to,--'tis a consummation",
                    "Devoutly to be wish'd. To die,--to sleep;--",
                    "To sleep! perchance to dream:--ay, there's the rub;",
                    "For in that sleep of death what dreams may come,",
                    "When we have shuffled off this mortal coil,",
                    "Must give us pause: there's the respect",
                    "That makes calamity of so long life;",
                    "For who would bear the whips and scorns of time,",
                    "The oppressor's wrong, the proud man's contumely,",
                    "The pangs of despis'd love, the law's delay,",
                    "The insolence of office, and the spurns",
                    "That patient merit of the unworthy takes,",
                    "When he himself might his quietus make",
                    "With a bare bodkin? who would these fardels bear,",
                    "To grunt and sweat under a weary life,",
                    "But that the dread of something after death,--",
                    "The undiscover'd country, from whose bourn",
                    "No traveller returns,--puzzles the will,",
                    "And makes us rather bear those ills we have",
                    "Than fly to others that we know not of?",
                    "Thus conscience does make cowards of us all;",
                    "And thus the native hue of resolution",
                    "Is sicklied o'er with the pale cast of thought;",
                    "And enterprises of great pith and moment,",
                    "With this regard, their currents turn awry,",
                    "And lose the name of action.--Soft you now!",
                    "The fair Ophelia!--Nymph, in thy orisons",
                    "Be all my sins remember'd."
            };
}