hadoop 开发---WordCount

参考http://hadoop.apache.org/docs/r2.7.6/hadoop-mapreduce-client/hadoop-mapreduce-client-core/MapReduceTutorial.html

eclipse 新建maven项目

pom 文件内容

<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>hadoop_mapreduce</groupId>

  <artifactId>WordCount</artifactId>

  <version>0.0.1-SNAPSHOT</version>

  <packaging>jar</packaging>

  <name>WordCount</name>

  <url>http://maven.apache.org</url>

  <properties>

    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>

  </properties>

  <dependencies>

  <dependency>

    <groupId>org.apache.hadoop</groupId>

    <artifactId>hadoop-client</artifactId>

    <version>2.8.0</version>

</dependency>

<!--  <dependency>

  <!-- https://mvnrepository.com/artifact/org.apache.phoenix/phoenix-core -->

        <dependency>

            <groupId>jdk.tools</groupId>

            <artifactId>jdk.tools</artifactId>

            <version>1.8</version>

            <scope>system</scope>

            <systemPath>C:\Program Files\Java\jdk1.8.0_151\lib\tools.jar</systemPath>

        </dependency>

  </dependencies>

</project>

注: 只需要hadoop-client包，如果引入hbase相关的包，很可能出现包冲突，运行会出现异常。

WordCount类代码

package hadoop_mapreduce.WordCount;

import java.io.IOException;

import java.io.InterruptedIOException;

import java.util.StringTokenizer;

import org.apache.hadoop.conf.Configuration;

import org.apache.hadoop.fs.Path;

import org.apache.hadoop.io.IntWritable;

import org.apache.hadoop.io.Text;

import org.apache.hadoop.mapreduce.Job;

import org.apache.hadoop.mapreduce.Mapper;

import org.apache.hadoop.mapreduce.Reducer;

import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;

import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

public class WordCount{

}

连接hadoop的配置文件位置如图

eclipse执行运行会报错: HADOOP_HOME and hadoop.home.dir are unset.

编译打包，放入linux系统

mvn clean

mvn compile

mvn pacakge

我将打包生成的WordCount-0.0.1-SNAPSHOT.jar放到了/home/hadoop-user/work目录

在linux 运行 hadoop jar WordCount-0.0.1-SNAPSHOT.jar hadoop_mapreduce.WordCount.WordCount hdfs://192.168.50.107:8020/input hdfs://192.168.50.107:8020/output

注: 我这里如果不带类路径就会报错，找不到WordCount类。把要分析的文件放入hdfs的input目录中，Output目录不用自己创建。最后生成的分析结果会存在于output目录中

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