<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>cn.edu.ruc.dbiir</groupId><artifactId>mrtest</artifactId><version>0.0.1-SNAPSHOT</version><packaging>jar</packaging><name>mrtest</name><url>http://maven.apache.org</url><properties><project.build.sourceEncoding>UTF-8</project.build.sourceEncoding><hadoop.version>2.6.5</hadoop.version></properties><dependencies><dependency><groupId>log4j</groupId><artifactId>log4j</artifactId><version>1.2.17</version>
</dependency><dependency><groupId>org.apache.hadoop</groupId><artifactId>hadoop-client</artifactId><version>${hadoop.version}</version>
</dependency><dependency><groupId>org.apache.hadoop</groupId><artifactId>hadoop-common</artifactId><version>${hadoop.version}</version>
</dependency><dependency><groupId>org.apache.hadoop</groupId><artifactId>hadoop-hdfs</artifactId><version>${hadoop.version}</version>
</dependency><dependency><groupId>junit</groupId><artifactId>junit</artifactId><version>3.8.1</version><scope>test</scope></dependency></dependencies>
</project>

nnpackage cn.edu.ruc.dbiir.mrtest;import java.io.IOException;import org.apache.hadoop.classification.InterfaceAudience.Public;
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.mapred.JobConf;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.Mapper.Context;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.log4j.BasicConfigurator;
import org.apache.log4j.Logger;public class WordCount {public static class WCMapper extends Mapper<LongWritable, Text, Text, IntWritable>{@Overrideprotected void map(LongWritable key, Text value,Context context)throws IOException, InterruptedException {// TODO Auto-generated method stub
//          super.map(key, value, context);String data = value.toString();String [] words = data.split(" ");Logger logger = Logger.getLogger(WCMapper.class);      logger.error("Map-key:"+key+"|"+"Map-value:"+value);for(String w:words) {context.write(new Text(w), new IntWritable(1));}}}public static class WCReducer extends Reducer<Text, IntWritable, Text, IntWritable>{@Overrideprotected void reduce(Text key, Iterable<IntWritable> value,Context context) throws IOException, InterruptedException {// TODO Auto-generated method stub
//          super.reduce(arg0, arg1, arg2);int total =0;Logger logger = Logger.getLogger(WordCount.class);logger.error("Map-key:"+key+"|"+"Map-value:"+value);for(IntWritable v:value) {total+=v.get();}context.write(key, new IntWritable(total));}}public static void main(String[] args) throws Exception{BasicConfigurator.configure();Configuration conf = new Configuration();conf.set("fs.defaultFS", "hdfs://db-01:9000");conf.set("mapreduce.framework.name", "yarn");conf.set("yarn.resourcemanager.hostname", "db-01");//1.创建一个job和任务入口Job job = Job.getInstance(conf);//        Job job = Job.getInstance(new Configuration());job.setJarByClass(WordCount.class);((JobConf)job.getConfiguration()).setJar("Your own path by maven install/mrtest/target/mrtest-0.0.1-SNAPSHOT.jar");//2.指定job的mapper和输出的类型<k2,v2>job.setMapperClass(WCMapper.class);job.setMapOutputKeyClass(Text.class);job.setMapOutputValueClass(IntWritable.class);//3.指定job的reducer和输出类型<k4,v4>job.setReducerClass(WCReducer.class);job.setOutputKeyClass(Text.class);job.setOutputValueClass(IntWritable.class);//4指定job的输入和输出FileInputFormat.setInputPaths(job, new Path(args[0]));FileOutputFormat.setOutputPath(job, new Path(args[1]));//5封装参数job.setNumReduceTasks(2);//6.提交job给yarnboolean res=job.waitForCompletion(true);}}