MapReduce中数据去重
输入如下的数据,统计其中的地址信息,并对输出的地址信息进行去重
实现方法:Map阶段输出的信息K2为想要去重的内容,利用Reduce阶段的聚合特点,对K2进行聚合,去重。在两阶段中,V2,V3,V4为Null
distinct.csv
bash
John,30,New York
Jane,25,Los Angeles
Tom,33,New York
Doe,45,Chicago
Sam,26,Los Angeles
- main
bash
package com.hadoop;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.streaming.io.InputWriter;
public class Main {
public static void main(String[] args) throws Exception {
Job job =Job.getInstance(new Configuration());
job.setJarByClass(Main.class);
job.setMapperClass(Map.class);
job.setMapOutputKeyClass(Text.class);//k2
job.setMapOutputValueClass(NullWritable.class);//v2
job.setReducerClass(Reduce.class);
job.setOutputKeyClass(Text.class);//k4
job.setOutputValueClass(NullWritable.class);//v4
FileInputFormat.setInputPaths(job,new Path(args[0]));
FileOutputFormat.setOutputPath(job,new Path(args[1]));
job.waitForCompletion(true);
}
}
- Map
bash
package com.hadoop;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;
import java.io.IOException;
//Los Angeles
public class Map extends Mapper<LongWritable, Text,Text, NullWritable> {
//Jane,25,Los Angeles
@Override
protected void map(LongWritable k1, Text v1,Context context)
throws IOException, InterruptedException {
String data =v1.toString();
String words[]=data.split(",");
context.write(new Text(words[2]),NullWritable.get());
}
}
- Reduce
bash
package com.hadoop;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Reducer;
import java.io.IOException;
public class Reduce extends Reducer<Text, NullWritable,Text,NullWritable> {
@Override
protected void reduce(Text k3, Iterable<NullWritable> v3,Context context)
throws IOException, InterruptedException {
context.write(k3,NullWritable.get());
}
}
- pom
bash
<?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.hadoop</groupId>
<artifactId>Mapreduce_Distinct</artifactId>
<version>1.0-SNAPSHOT</version>
<name>Mapreduce_Distinct</name>
<description>wunaiieq</description>
<properties>
<maven.compiler.source>8</maven.compiler.source>
<maven.compiler.target>8</maven.compiler.target>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<!--版本控制-->
<hadoop.version>2.7.3</hadoop.version>
</properties>
<dependencies>
<dependency>
<groupId>org.apache.hadoop</groupId>
<artifactId>hadoop-common</artifactId>
<version>${hadoop.version}</version>
</dependency>
<dependency>
<groupId>org.apache.hadoop</groupId>
<artifactId>hadoop-hdfs</artifactId>
<version>${hadoop.version}</version>
</dependency>
<dependency>
<groupId>org.apache.hadoop</groupId>
<artifactId>hadoop-mapreduce-client-core</artifactId>
<version>${hadoop.version}</version>
</dependency>
<dependency>
<groupId>org.apache.hadoop</groupId>
<artifactId>hadoop-client</artifactId>
<version>${hadoop.version}</version>
</dependency>
<dependency>
<groupId>org.apache.hadoop</groupId>
<artifactId>hadoop-yarn-api</artifactId>
<version>${hadoop.version}</version>
</dependency>
<dependency>
<groupId>org.apache.hadoop</groupId>
<artifactId>hadoop-streaming</artifactId>
<version>${hadoop.version}</version>
</dependency>
</dependencies>
<!--构建配置-->
<build>
<plugins>
<plugin>
<!--声明-->
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-assembly-plugin</artifactId>
<version>3.3.0</version>
<!--具体配置-->
<configuration>
<archive>
<manifest>
<!--jar包的执行入口-->
<mainClass>com.hadoop.Main</mainClass>
</manifest>
</archive>
<descriptorRefs>
<!--描述符,此处为预定义的,表示创建一个包含项目所有依赖的可执行 JAR 文件;
允许自定义生成jar文件内容-->
<descriptorRef>jar-with-dependencies</descriptorRef>
</descriptorRefs>
</configuration>
<!--执行配置-->
<executions>
<execution>
<!--执行配置ID,可修改-->
<id>make-assembly</id>
<!--执行的生命周期-->
<phase>package</phase>
<goals>
<!--执行的目标,single表示创建一个分发包-->
<goal>single</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
</project>
- 效果