【跟小嘉学 Apache Flink】二、Flink 快速上手

系列文章目录

【跟小嘉学 Apache Flink】一、Apache Flink 介绍
【跟小嘉学 Apache Flink】二、Flink 快速上手

一、创建工程

1.1、创建 Maven 工程

创建 maven 工程 并且添加如下依赖

<?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>org.xiaojia</groupId>
    <artifactId>flinkdemo</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>jar</packaging>

    <properties>
        <maven.compiler.source>19</maven.compiler.source>
        <maven.compiler.target>19</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <dependencies>
        <!-- https://mvnrepository.com/artifact/org.apache.flink/flink-streaming-java -->
        <dependency>
            <groupId>org.apache.flink</groupId>
            <artifactId>flink-streaming-java</artifactId>
            <version>1.17.1</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/org.apache.flink/flink-clients -->
        <dependency>
            <groupId>org.apache.flink</groupId>
            <artifactId>flink-clients</artifactId>
            <version>1.17.1</version>
        </dependency>


    </dependencies>

</project>

1.2、log4j 配置

在 resource 目录下创建 log4j.properties 文件，写入如下内容

log4j.rootLogger=error,stdout
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%-4r [%t] %-5p %c %x - %m%n

二、批处理单词统计（DataSet API）

2.1、创建 BatchWordCount 类型

package org.xiaojia.demo.wc;

import org.apache.flink.api.common.typeinfo.Types;
import org.apache.flink.api.java.ExecutionEnvironment;
import org.apache.flink.api.java.operators.AggregateOperator;
import org.apache.flink.api.java.operators.DataSource;
import org.apache.flink.api.java.operators.FlatMapOperator;
import org.apache.flink.api.java.operators.UnsortedGrouping;
import org.apache.flink.api.java.tuple.Tuple2;
import org.apache.flink.util.Collector;

public class BatchWordCount {
    public static void main(String[] args) {
        // 1、创建执行环境
        ExecutionEnvironment executionEnvironment = ExecutionEnvironment.getExecutionEnvironment();

        // 2、 从文件读取数据
        DataSource<String> lineDataSource = executionEnvironment.readTextFile("input/words.txt");

        // 3、将每一行数据进行分词，转换为二元组类型
        FlatMapOperator<String, Tuple2<String, Long>>  wordAndOneTuple = lineDataSource.flatMap((String line, Collector<Tuple2<String, Long>> collector) -> {
            String[] words = line.split(" ");
            for (String word : words) {
                collector.collect(Tuple2.of(word, 1L));
            }
        }).returns(Types.TUPLE(Types.STRING, Types.LONG));

        // 4、按照 word 进行分组
        UnsortedGrouping<Tuple2<String, Long>> wordAndOneGroup = wordAndOneTuple.groupBy(0);

        // 5、分组内进行聚合统计
        AggregateOperator<Tuple2<String, Long>> sum = wordAndOneGroup.sum(1);

        try {
            sum.print();
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }
}

2.4、运行结果

实际上在 Flink 里面已经做到流批处理统一，官方推荐使用 DateStream API，在跳任务时通过执行模式设置为 Batch 来进行批处理

bin/fliink run -Dexecution.runtime-mode=BATCH BatchWordCount.jar

三、流处理单词统计（DataSet API）

使用 DataSet API可以很容易实现批处理。对于Flink而言，流处理才是处理逻辑的底层核心，所以流批统一之后的 DataStream API 更加强大，可以直接处理批处理和流处理的所有场景。

在 Flink 的视角里，一切数据都可以认为是流，流数据是无界流，而批数据是有界流。所以批处理，其实可以看作是有界流的处理。

3.1、读取文件流

3.1.1、过时的写法

package org.xiaojia.demo.wc.stream;

import org.apache.flink.api.common.typeinfo.Types;
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;
import org.apache.flink.util.Collector;

public class BoundStreamWordCount {
    public static void main(String[] args) throws Exception {
        // 1、创建流式的执行环境
        StreamExecutionEnvironment streamExecutionEnvironment = StreamExecutionEnvironment.getExecutionEnvironment();

        // 2、读取文件
        DataStreamSource<String> lineDataStreamSource = streamExecutionEnvironment.readTextFile("input/words.txt");

        // 3、将每一行数据进行分词，转换为二元组类型
        SingleOutputStreamOperator<Tuple2<String, Long>> wordAndOneTuple = lineDataStreamSource.flatMap((String line, Collector<Tuple2<String, Long>> collector) -> {
            String[] words = line.split(" ");
            for (String word : words) {
                collector.collect(Tuple2.of(word, 1L));
            }
        }).returns(Types.TUPLE(Types.STRING, Types.LONG));

        // 4、按照 word 进行分组
        KeyedStream<Tuple2<String, Long>, String> wordAndOneKeyStream = wordAndOneTuple.keyBy((data) -> data.f0);

        // 5、求和
        SingleOutputStreamOperator<Tuple2<String, Long>> sum = wordAndOneKeyStream.sum(1);

        // 6、打印
        sum.print();

        // 7、执行等待
        streamExecutionEnvironment.execute();

    }
}

3.1.2、执行错误的处理

Unable to make field private final byte[] java.lang.String.value accessible: module java.base does not "opens java.lang" to unnamed module
    @7ce6a65d

如果出现上述类似错误，解决方案，通过添加 VM参数打开对应模块的对应模块包

--add-opens java.base/java.lang=ALL-UNNAMED 
--add-opens java.base/java.util=ALL-UNNAMED

3.1.3、执行结果

3.1.4、readTextFile 过时问题

解决方案可以按照提示给出的 使用 FileSource（需要用到Flink的连接器）

<dependency>
  <groupId>org.apache.flink</groupId>
  <artifactId>flink-connector-files</artifactId>
  <version>${flink.version}</version>
</dependency>

3.2、读取 socket 网络流

3.2.1、读取socket 流代码

package org.xiaojia.demo.wc.stream;

import org.apache.flink.api.common.typeinfo.Types;
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;
import org.apache.flink.util.Collector;

public class StreamWordCount {
    public static void main(String[] args) throws Exception {
        // 1、创建流式的执行环境
        StreamExecutionEnvironment streamExecutionEnvironment = StreamExecutionEnvironment.getExecutionEnvironment();

        // 2、读取socket流
        String hostname = "127.0.0.1";
        int port = 8888;
        DataStreamSource<String> lineDataStreamSource = streamExecutionEnvironment.socketTextStream(hostname, port);

        // 3、将每一行数据进行分词，转换为二元组类型
        SingleOutputStreamOperator<Tuple2<String, Long>> wordAndOneTuple = lineDataStreamSource.flatMap((String line, Collector<Tuple2<String, Long>> collector) -> {
            String[] words = line.split(" ");
            for (String word : words) {
                collector.collect(Tuple2.of(word, 1L));
            }
        }).returns(Types.TUPLE(Types.STRING, Types.LONG));

        // 4、按照 word 进行分组
        KeyedStream<Tuple2<String, Long>, String> wordAndOneKeyStream = wordAndOneTuple.keyBy((data) -> data.f0);

        // 5、求和
        SingleOutputStreamOperator<Tuple2<String, Long>> sum = wordAndOneKeyStream.sum(1);

        // 6、打印
        sum.print();

        // 7、执行等待
        streamExecutionEnvironment.execute();
    }
}

3.2.2、使用 nc 监听端口

(base) xiaojiadeMacBook-Pro:~ xiaojia$ nc -lk 8888
hello java
hello flink
hello world

3.2.3、执行结果

此时，只要有数据进来，就会统计

3.2.4、从命令行参数获取主机名和端口号

package org.xiaojia.demo.wc.stream;

import org.apache.flink.api.common.typeinfo.Types;
import org.apache.flink.api.java.tuple.Tuple2;
import org.apache.flink.api.java.utils.ParameterTool;
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;
import org.apache.flink.util.Collector;

public class StreamWordCount {
    public static void main(String[] args) throws Exception {
        // 1、创建流式的执行环境
        StreamExecutionEnvironment streamExecutionEnvironment = StreamExecutionEnvironment.getExecutionEnvironment();

        // 2、读取socket流

        ParameterTool parameterTool = ParameterTool.fromArgs(args);

        String hostname = parameterTool.get("host");
        int port = parameterTool.getInt("port");
        DataStreamSource<String> lineDataStreamSource = streamExecutionEnvironment.socketTextStream(hostname, port);

        // 3、将每一行数据进行分词，转换为二元组类型
        SingleOutputStreamOperator<Tuple2<String, Long>> wordAndOneTuple = lineDataStreamSource.flatMap((String line, Collector<Tuple2<String, Long>> collector) -> {
            String[] words = line.split(" ");
            for (String word : words) {
                collector.collect(Tuple2.of(word, 1L));
            }
        }).returns(Types.TUPLE(Types.STRING, Types.LONG));

        // 4、按照 word 进行分组
        KeyedStream<Tuple2<String, Long>, String> wordAndOneKeyStream = wordAndOneTuple.keyBy((data) -> data.f0);

        // 5、求和
        SingleOutputStreamOperator<Tuple2<String, Long>> sum = wordAndOneKeyStream.sum(1);

        // 6、打印
        sum.print();

        // 7、执行等待
        streamExecutionEnvironment.execute();
    }
}

命令行参数传递
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