apache flink hello world 示例 wordcount

最新推荐文章于 2025-01-16 16:21:06 发布

stonexmx

最新推荐文章于 2025-01-16 16:21:06 发布

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分类专栏： flink 文章标签： flink 实时计算大数据 demo

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本文通过一个简单的'WordCount'示例，介绍如何使用Apache Flink进行实时计算。首先启动监听服务，然后创建一个Maven工程，添加Flink依赖，并编写程序代码。运行main方法后，可以在监听服务端口输入数据，程序会实时处理并每隔5秒更新输出结果，窗口期为20000秒。

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1. 启动服务监听端口

C:\Users\Administrator>nc -L -p 9000

我的是windows，若是linux 则用 nc -l 9000 即可

2. demo工程

maven dependecy


    <dependencies>
        <!-- https://mvnrepository.com/artifact/org.apache.flink/flink-java -->
        <dependency>
            <groupId>org.apache.flink</groupId>
            <artifactId>flink-java</artifactId>
            <version>1.7.2</version>
        </dependency>

        <dependency>
            <groupId>org.apache.flink</groupId>
            <artifactId>flink-streaming-java_2.12</artifactId>
            <version>1.7.2</version>
        </dependency>

        <dependency>
            <groupId>org.apache.flink</groupId>
            <artifactId>flink-clients_2.12</artifactId>
            <version>1.7.2</version>
        </dependency>


    </dependencies>

程序代码

import org.apache.flink.api.common.functions.FlatMapFunction;
import org.apache.flink.api.java.utils.ParameterTool;
import org.apache.flink.streaming.api.datastream.DataStream;
import org.apache.flink.streaming.api.datastream.DataStreamSource;
import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
import org.apache.flink.streaming.api.windowing.time.Time;
import org.apache.flink.util.Collector;

public class WordCount {

    public static void main(String[] args) throws Exception {
        //定义socket的端口号
        int port;
        try{
            ParameterTool parameterTool = ParameterTool.fromArgs(args);
            port = parameterTool.getInt("port");
        }catch (Exception e){
            System.err.println("没有指定port参数，使用默认值9000");
            port = 9000;
        }

        //获取运行环境
        StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();

        //连接socket获取输入的数据
        DataStreamSource<String> text = env.socketTextStream("127.0.0.1", port, "\n");

        //计算数据
        DataStream<WordWithCount> windowCount = text.flatMap(new FlatMapFunction<String, WordWithCount>() {
            public void flatMap(String value, Collector<WordWithCount> out) throws Exception {
                String[] splits = value.split("\\s");
                for (String word:splits) {
                    out.collect(new WordWithCount(word,1L));
                }
            }
        })//打平操作，把每行的单词转为<word,count>类型的数据
                .keyBy("word")//针对相同的word数据进行分组
                .timeWindow(Time.seconds(20000),Time.seconds(5))//指定计算数据的窗口大小和滑动窗口大小
                .sum("count");

        //把数据打印到控制台
        windowCount.print()
                .setParallelism(1);//使用一个并行度
        //注意：因为flink是懒加载的，所以必须调用execute方法，上面的代码才会执行
        env.execute("streaming word count");

    }

    /**
     * 主要为了存储单词以及单词出现的次数
     */
    public static class WordWithCount{
        public String word;
        public long count;
        public WordWithCount(){}
        public WordWithCount(String word, long count) {
            this.word = word;
            this.count = count;
        }

        @Override
        public String toString() {
            return "WordWithCount{" +
                    "word='" + word + '\'' +
                    ", count=" + count +
                    '}';
        }
    }


}

运行 main

"C:\Program Files\Java\jdk1.8.0_172\bin\java.exe" .....
没有指定port参数，使用默认值9000
SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder".
SLF4J: Defaulting to no-operation (NOP) logger implementation
SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further details.

3. 测试

在监听服务端输入

C:\Users\Administrator>nc -L -p 9000
hello flink
what's the flink ?

程序代码的输出结果

WordWithCount{word='flink', count=1}
WordWithCount{word='hello', count=1}

......

WordWithCount{word='flink', count=2}
WordWithCount{word='?', count=1}
WordWithCount{word='the', count=1}
WordWithCount{word='hello', count=1}
WordWithCount{word='what's', count=1}

.......

输出会根据输入不停的刷新

刷新机制是根据代码中的

.timeWindow(Time.seconds(20000),Time.seconds(5))

设定的，这里设定的是在20000秒的窗口期内，每5秒刷新下结果