package com.ares.hadoop.mr.wordcount;import java.io.IOException;import java.util.StringTokenizer;import org.apache.hadoop.io.LongWritable;import org.apache.hadoop.io.Text;import org.apache.hadoop.mapreduce.Mapper;//Long, String, String, Long --> LongWritable, Text, Text, LongWritablepublic class WordCountMapper extends Mapper<LongWritable, Text, Text, LongWritable> {    private final static LongWritable ONE = new LongWritable(1L) ;    private Text word = new Text();        @Override    protected void map(LongWritable key, Text value,            Mapper<LongWritable, Text, Text, LongWritable>.Context context)            throws IOException, InterruptedException {        // TODO Auto-generated method stub        //super.map(key, value, context);        StringTokenizer itr = new StringTokenizer(value.toString(), " ");        while (itr.hasMoreTokens()) {            //efficiency is not well            //context.write(new Text(itr.nextToken()), new LongWritable(1L));            word.set(itr.nextToken());            context.write(word, ONE);                    }    }}

package com.ares.hadoop.mr.wordcount;import java.io.IOException;import org.apache.hadoop.io.LongWritable;import org.apache.hadoop.io.Text;import org.apache.hadoop.mapreduce.Reducer;public class WordCountReducer extends Reducer<Text, LongWritable, Text, LongWritable>{    private LongWritable result = new LongWritable();        @Override    protected void reduce(Text key, Iterable<LongWritable> vlaues,            Reducer<Text, LongWritable, Text, LongWritable>.Context context)            throws IOException, InterruptedException {        // TODO Auto-generated method stub        //super.reduce(arg0, arg1, arg2);        long sum = 0;        for (LongWritable value : vlaues) {            sum += value.get();        }        result.set(sum);        context.write(key, result);    }}

package com.ares.hadoop.mr.wordcount;import java.io.IOException;import org.apache.hadoop.conf.Configuration;import org.apache.hadoop.fs.Path;import org.apache.hadoop.io.LongWritable;import org.apache.hadoop.io.Text;import org.apache.hadoop.mapreduce.Job;import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;import org.apache.log4j.Logger;public class MRTest {    private static final Logger LOGGER = Logger.getLogger(MRTest.class);        public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {        LOGGER.debug("MRTest: MRTest STARTED...");                if (args.length != 2) {            LOGGER.error("MRTest: ARGUMENTS ERROR");            System.exit(-1);        }                Configuration conf = new Configuration();        Job job = Job.getInstance(conf);                // JOB NAME        job.setJobName("wordcount");                // JOB MAPPER & REDUCER        job.setJarByClass(MRTest.class);        job.setMapperClass(WordCountMapper.class);        job.setReducerClass(WordCountReducer.class);                // MAP & REDUCE        job.setOutputKeyClass(Text.class);        job.setOutputValueClass(LongWritable.class);        // MAP        job.setMapOutputKeyClass(Text.class);        job.setMapOutputValueClass(LongWritable.class);                // JOB INPUT & OUTPUT PATH        //FileInputFormat.addInputPath(job, new Path(args[0]));        FileInputFormat.setInputPaths(job, args[0]);        FileOutputFormat.setOutputPath(job, new Path(args[1]));                // VERBOSE OUTPUT        if (job.waitForCompletion(true)) {            LOGGER.debug("MRTest: MRTest SUCCESSFULLY...");        } else {            LOGGER.debug("MRTest: MRTest FAILED...");        }                LOGGER.debug("MRTest: MRTest COMPLETED...");    }}

hadoop jar wordcount.jar com.ares.hadoop.mr.wordcount.MRTest hdfs://HADOOP-NODE1:9000/word-count/input hdfs://HADOOP-NODE1:9000/word-count/output