Flink中wordcount写法

import org.apache.flink.api.common.functions.FlatMapFunction;
import org.apache.flink.api.common.typeinfo.TypeHint;
import org.apache.flink.api.common.typeinfo.TypeInformation;
import org.apache.flink.api.java.functions.KeySelector;
import org.apache.flink.api.java.tuple.Tuple2;
import org.apache.flink.streaming.api.datastream.DataStreamSource;
import org.apache.flink.streaming.api.datastream.KeyedStream;
import org.apache.flink.streaming.api.datastream.SingleOutputStreamOperator;
import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;

/**
 * @Author: J
 * @Version: 1.0
 * @CreateTime: 2023/6/13
 * @Description: 测试代码
 **/
public class FlinkWordCountSocket {
    public static void main(String[] args) throws Exception {
        // 创建数据流环境
        StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
        // 以Socket作为数据源
        DataStreamSource<String> socketSource = env.socketTextStream("localhost", 9999);
        //env.setRuntimeMode(RuntimeExecutionMode.BATCH); // 如果想改成批处理就加上这行代码
        // 通过flapMap对数据进行转换
        SingleOutputStreamOperator<Tuple2<String, Integer>> tupleDataStream = socketSource.flatMap((FlatMapFunction<String, Tuple2<String, Integer>>) (s, collector) -> {
            String[] split = s.split(" "); // 切分单词
            for (String word : split) {
                collector.collect(Tuple2.of(word, 1)); // 将单词以Tuple2的形式返回'(word, 1)'
            }
        }).returns(TypeInformation.of(new TypeHint<Tuple2<String, Integer>>() {})); // Tuple2是flink中提供的类型java无法自动推断,所以加上这段代码
        // 根据单词进行分组
        KeyedStream<Tuple2<String, Integer>, String> keyed = tupleDataStream.keyBy((KeySelector<Tuple2<String, Integer>, String>) stringIntegerTuple2 -> stringIntegerTuple2.f0);
        // 根据单词进行聚合
        SingleOutputStreamOperator<Tuple2<String, Integer>> result = keyed.sum("f1"); // 这里的参数填索引或者f1都可,f1可理解为字段名
        result.print();
        env.execute();
    }
}

代码中注释写的很清楚了,这里就不啰嗦代码的内容了,说一下注意点

1. 导包的时候千万要注意不要导成scala的包(如Tuple2等)
2. Socket我这里使用的是本地的socket服务,linux和windows不同,这个自行搜索如何安装相关服务,这里说一下linux中启动一个socket服务的命令nc -lk 端口号
3. 友情提示idea中ctrl+p可快速查看方法中应该传入什么参数.