Flink WordCount 之lamda版

学习Flink的时候第一个入门程序WordCount，官方给的使用匿名类实现方法，这样看起来代码不简洁。于是想用lamda改写下，踩了不少坑，记录下。

Table of Contents

官方给定版本

Lamda第一版 POJO版

 错误1：Collector无泛型参数错误

错误2： .keyBy("word") 类型不能做key的错误

Lamda第二版 Tuple2版

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flink 版本 1.9 

https://ci.apache.org/projects/flink/flink-docs-release-1.9/getting-started/tutorials/local_setup.html

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官方给定版本

public class SocketWindowWordCount {

    public static void main(String[] args) throws Exception {

        // the port to connect to
        final int port;
        try {
            final ParameterTool params = ParameterTool.fromArgs(args);
            port = params.getInt("port");
        } catch (Exception e) {
            System.err.println("No port specified. Please run 'SocketWindowWordCount --port <port>'");
            return;
        }

        // get the execution environment
        final StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();

        // get input data by connecting to the socket
        DataStream<String> text = env.socketTextStream("localhost", port, "\n");

        // parse the data, group it, window it, and aggregate the counts
        DataStream<WordWithCount> windowCounts = text
            .flatMap(new FlatMapFunction<String, WordWithCount>() {
                @Override
                public void flatMap(String value, Collector<WordWithCount> out) {
                    for (String word : value.split("\\s")) {
                        out.collect(new WordWithCount(word, 1L));
                    }
                }
            })
            .keyBy("word")
            .timeWindow(Time.seconds(5), Time.seconds(1))
            .reduce(new ReduceFunction<WordWithCount>() {
                @Override
                public Word