Hadoop学习笔记——WordCount
Posted tags:
篇首语:本文由小常识网(cha138.com)小编为大家整理,主要介绍了Hadoop学习笔记——WordCount相关的知识,希望对你有一定的参考价值。
1.在IDEA下新建工程,选择from Mevan
GroupId:WordCount
ArtifactId:com.hadoop.1st
Project name:WordCount
2.pom.xml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>WordCount</groupId> <artifactId>com.hadoop.1st</artifactId> <version>1.0-SNAPSHOT</version> <repositories> <repository> <id>apache</id> <url>http://maven.apache.org</url> </repository> </repositories> <dependencies> <dependency> <groupId>org.apache.hadoop</groupId> <artifactId>hadoop-core</artifactId> <version>1.2.1</version> </dependency> <dependency> <groupId>org.apache.hadoop</groupId> <artifactId>hadoop-common</artifactId> <version>2.7.1</version> </dependency> </dependencies> <build> <plugins> <plugin> <artifactId>maven-dependency-plugin</artifactId> <configuration> <excludeTransitive>false</excludeTransitive> <stripVersion>true</stripVersion> <outputDirectory>./lib</outputDirectory> </configuration> </plugin> </plugins> </build> </project>
3.main/java目录下新建WordCount.java文件
import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.fs.Path; import org.apache.hadoop.io.IntWritable; import org.apache.hadoop.io.LongWritable; 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.input.TextInputFormat; import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat; import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat; import java.io.IOException; import java.util.StringTokenizer; /** * Created by common on 17-3-26. */ public class WordCount { public static class WordCountMap extends Mapper<LongWritable, Text, Text, IntWritable> { private final IntWritable one = new IntWritable(1); private Text word = new Text(); public void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException { String line = value.toString(); StringTokenizer token = new StringTokenizer(line); while (token.hasMoreTokens()) { word.set(token.nextToken()); context.write(word, one); } } } public static class WordCountReduce extends Reducer<Text, IntWritable, Text, IntWritable> { public void reduce(Text key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException { int sum = 0; for (IntWritable val : values) { sum += val.get(); } context.write(key, new IntWritable(sum)); } } public static void main(String[] args) throws Exception { Configuration conf = new Configuration(); Job job = new Job(conf); job.setJarByClass(WordCount.class); job.setJobName("wordcount"); job.setOutputKeyClass(Text.class); job.setOutputValueClass(IntWritable.class); job.setMapperClass(WordCountMap.class); job.setReducerClass(WordCountReduce.class); job.setInputFormatClass(TextInputFormat.class); job.setOutputFormatClass(TextOutputFormat.class); FileInputFormat.addInputPath(job, new Path(args[0])); FileOutputFormat.setOutputPath(job, new Path(args[1])); job.waitForCompletion(true); } }
4.在src同级目录下新建input目录,以及下面的test.segmented文件
test.segmented文件内容
aa bb cc dd aa cc ee ff ff gg hh aa
4.在run configuration下设置运行方式为Application
5.运行java文件,将会生成output目录,part-r-00000为运行的结果,下次运行必须删除output目录,否则会报错
以上是关于Hadoop学习笔记——WordCount的主要内容,如果未能解决你的问题,请参考以下文章
hadoop学习笔记:运行wordcount对文件字符串进行统计案例