【Flink】Flink基础之WordCount实例（Java与Scala版本）

简述

WordCount（单词计数）一直是大数据入门的经典案例，下面用java和scala实现Flink的WordCount代码；

采用IDEA + Maven + Flink 环境；文末附 pom 文件和相关技术点总结；

Java实现Flink批处理版本

import org.apache.flink.api.common.functions.FlatMapFunction;
import org.apache.flink.api.java.DataSet;
import org.apache.flink.api.java.ExecutionEnvironment;
import org.apache.flink.api.java.tuple.Tuple2;
import org.apache.flink.util.Collector;

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

        // 创建执行环境
        ExecutionEnvironment env = ExecutionEnvironment.getExecutionEnvironment();

        // 加载或创建源数据
        DataSet<String> text = env.fromElements("this a book", "i love china", "i am chinese");

        // 转化处理数据
        DataSet<Tuple2<String, Integer>> ds = text.flatMap(new LineSplitter()).groupBy(0).sum(1);

        // 输出数据到目的端
        ds.print();

        // 执行任务操作
        // 由于是Batch操作，当DataSet调用print方法时，源码内部已经调用Excute方法，所以此处不再调用，如果调用会出现错误
        //env.execute("Flink Batch Word Count By Java");

    }

    static class LineSplitter implements FlatMapFunction<String, Tuple2<String,Integer>> {
        @Override
        public void flatMap(String line, Collector<Tuple2<String, Integer>> collector) throws Exception {
            for (String word:line.split(" ")) {
                collector.collect(new Tuple2<>(word,1));
            }
        }
    }
}

运行输出结果如下：

(a,1)
(am,1)
(love,1)
(china,1)
(this,1)
(i,2)
(book,1)
(chinese,1)

Java实现Flink流处理版本

import org.apache.flink.api.common.functions.FlatMapFunction;
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 WordCountStreamingByJava {
    public static void main(String[] args) throws Exception {

        // 创建执行环境
        StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
        // 设置socket数据源
        DataStreamSource<String> source = env.socketTextStream("192.168.1.111", 9999, "\n");
        // 转化处理数据
        DataStream<WordWithCount> dataStream = source.flatMap(new FlatMapFunction<String, WordWithCount>() {
            @Override
            public void flatMap(String line, Collector<WordWithCount> collector) throws Exception {
                for (String word : line.split(" ")) {
                    collector.collect(new WordWithCount(word, 1));
                }
            }
        }).keyBy("word")//以key分组统计
                .timeWindow(Time.seconds(2),Time.seconds(2))//设置一个窗口函数，模拟数据流动
                .sum("count");//计算时间窗口内的词语个数

        // 输出数据到目的端
        dataStream.print();

        // 执行任务操作
        env.execute("Flink Streaming Word Count By Java");

    }

    public static class WordWithCount{
        public String word;
        public int count;

        public WordWithCount(){

        }

        public WordWithCount(String word, int count) {
            this.word = word;
            this.count = count;
        }

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

启动一个shell窗口，联通9999端口，输入数据：

[root@spark111 flink-1.6.2]# nc -l 9999
山东 天津 北京 河北 河南 山东 上海 北京
山东 海南 青海 西藏 四川 海南

IDEA 输出结果如下：

4> WordWithCount{word='北京', count=2}
1> WordWithCount{word='上海', count=1}
5> WordWithCount{word='天津', count=1}
4> WordWithCount{word='河南', count=1}
7> WordWithCount{word='山东', count=2}
3> WordWithCount{word='河北', count=1}
------------------------为了区分前后时间窗口结果，手动加的这条线--------------------------
8> WordWithCount{word='海南', count=2}
8> WordWithCount{word='四川', count=1}
7> WordWithCount{word='山东', count=1}
1> WordWithCount{word='西藏', count=1}
5> WordWithCount{word='青海', count=1}

Scala实现Flink批处理版本

import org.apache.flink.api.scala._
import org.apache.flink.api.scala.ExecutionEnvironment

object WordCountBatchByScala {
  def main(args: Array[String]): Unit = {

    //获取执行环境
    val env = ExecutionEnvironment.getExecutionEnvironment

    //加载数据源
    val source = env.fromElements("china is the best country","beijing is the capital of china")

    //转化处理数据
    val ds = source.flatMap(_.split(" ")).map((_,1)).groupBy(0).sum(1)

    //输出至目的端
    ds.print()

    // 执行操作
    // 由于是Batch操作，当DataSet调用print方法时，源码内部已经调用Excute方法，所以此处不再调用，如果调用会出现错误
    //env.execute("Flink Batch Word Count By Scala")

  }
}

运行结果如下：

(is,2)
(beijing,1)
(the,2)
(china,2)
(country,1)
(of,1)
(best,1)
(capital,1)

Scala实现Flink流处理版本

import org.apache.flink.streaming.api.scala._
import org.apache.flink.streaming.api.scala.StreamExecutionEnvironment
import org.apache.flink.streaming.api.windowing.time.Time

object WordCountStreamingByScala {
  def main(args: Array[String]): Unit = {

    //获取执行环境
    val env = StreamExecutionEnvironment.getExecutionEnvironment

    //加载或创建数据源
    val source = env.socketTextStream("192.168.1.111",9999,'\n')

    //转化处理数据
    val dataStream = source.flatMap(_.split(" "))
      .map((_,1))
      .keyBy(0)
      .timeWindow(Time.seconds(2),Time.seconds(2))
      .sum(1)

    //输出到目的端
    dataStream.print()

    //执行操作
    env.execute("Flink Streaming Word Count By Scala")

  }
}

启动shell窗口，开启9999端口通信，输入词语：

[root@spark111 flink-1.6.2]# nc -l 9999
time is passed what is the time?
time is nine time passed again

运行结果如下：

4> (what,1)
5> (time,1)
8> (is,2)
5> (time?,1)
8> (passed,1)
5> (the,1)
------------------------为了区分前后时间窗口结果，手动加的这条线--------------------------
8> (is,1)
5> (time,2)
8> (passed,1)
7> (nine,1)
6> (again,1)

POM文件

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.ssrs</groupId>
    <artifactId>flinkdemo</artifactId>
    <version>1.0</version>

    <properties>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
        <encoding>UTF-8</encoding>
        <scala.version>2.11.12</scala.version>
        <scala.binary.version>2.11</scala.binary.version>
        <hadoop.version>2.8.4</hadoop.version>
        <flink.version>1.6.1</flink.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.scala-lang</groupId>
            <artifactId>scala-library</artifactId>
            <version>${scala.version}</version>
        </dependency>
        <dependency>
            <groupId>org.apache.flink</groupId>
            <artifactId>flink-java</artifactId>
            <version>${flink.version}</version>
        </dependency>
        <dependency>
            <groupId>org.apache.flink</groupId>
            <artifactId>flink-streaming-java_${scala.binary.version}</artifactId>
            <version>${flink.version}</version>
        </dependency>
        <dependency>
            <groupId>org.apache.flink</groupId>
            <artifactId>flink-scala_${scala.binary.version}</artifactId>
            <version>${flink.version}</version>
        </dependency>
        <dependency>
            <groupId>org.apache.flink</groupId>
            <artifactId>flink-streaming-scala_${scala.binary.version}</artifactId>
            <version>${flink.version}</version>
        </dependency>
        <dependency>
            <groupId>org.apache.flink</groupId>
            <artifactId>flink-table_${scala.binary.version}</artifactId>
            <version>${flink.version}</version>
        </dependency>
        <dependency>
            <groupId>org.apache.flink</groupId>
            <artifactId>flink-clients_${scala.binary.version}</artifactId>
            <version>${flink.version}</version>
        </dependency>
        <dependency>
            <groupId>org.apache.hadoop</groupId>
            <artifactId>hadoop-client</artifactId>
            <version>${hadoop.version}</version>
        </dependency>
    </dependencies>
</project>

总结

1. flink处理任务流程如下：

   ​ ① 获取执行环境 （Environment）

   ​ ② 加载或者创建数据源（source）

   ​ ③ 转化处理数据（transformation）

   ​ ④ 输出目的端（sink）

   ​ ⑤ 执行任务（execute）

2. 在批处理中，如果输出目的端，执行的 print 命令（除此之外，还有count，collect方法），则执行任务Execute不需要调用（因为这些方法内部已经调用了Execute方法）；如果调用，虽然也有正确结果，但是会有错误信息输出；错误如下：

   Exception in thread "main" java.lang.RuntimeException: No new data sinks have been defined since the last execution. The last execution refers to the latest call to 'execute()', 'count()', 'collect()', or 'print()'.
   	at org.apache.flink.api.java.ExecutionEnvironment.createProgramPlan(ExecutionEnvironment.java:940)
   	at org.apache.flink.api.java.ExecutionEnvironment.createProgramPlan(ExecutionEnvironment.java:922)
   	at org.apache.flink.api.java.LocalEnvironment.execute(LocalEnvironment.java:85)
   	at com.ssrs.WordCountBatchByJava.main(WordCountBatchByJava.java:27)
   

3. 如果批处理代码中，输出目的端调用writeAsCsv、writeAsText等其他方法，则后面需要调用Execute；

4. 批处理获取执行环境用ExecutionEnvironment，流处理获取环境用StreamExecutionEnvironment

5. 批处理后的数据是DataSet，流处理后的数据是DataStream.