转：http://blog.csdn.net/jediael_lu/article/details/38705371

以下程序在hadoop1.2.1上测试成功。

本例先将源代码呈现，然后详细说明执行步骤，最后对源代码及执行过程进行分析。

一、源代码

1 package org.jediael.hadoopdemo.wordcount;   2    3 import java.io.IOException;   4 import java.util.StringTokenizer;   5    6 import org.apache.hadoop.conf.Configuration;   7 import org.apache.hadoop.fs.Path;   8 import org.apache.hadoop.io.IntWritable;   9 import org.apache.hadoop.io.LongWritable;  10 import org.apache.hadoop.io.Text;  11 import org.apache.hadoop.mapreduce.Job;  12 import org.apache.hadoop.mapreduce.Mapper;  13 import org.apache.hadoop.mapreduce.Reducer;  14 import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;  15 import org.apache.hadoop.mapreduce.lib.input.TextInputFormat;  16 import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;  17 import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;  18   19 public class WordCount {  20   21     public static class WordCountMap extends  22             Mapper
     
       {  23   24         private final IntWritable one = new IntWritable(1);  25         private Text word = new Text();  26   27         public void map(LongWritable key, Text value, Context context)  28                 throws IOException, InterruptedException {  29             String line = value.toString();  30             StringTokenizer token = new StringTokenizer(line);  31             while (token.hasMoreTokens()) {  32                 word.set(token.nextToken());  33                 context.write(word, one);  34             }  35         }  36     }  37   38     public static class WordCountReduce extends  39             Reducer
      
        {  40   41         public void reduce(Text key, Iterable
       
         values,  42                 Context context) throws IOException, InterruptedException {  43             int sum = 0;  44             for (IntWritable val : values) {  45                 sum += val.get();  46             }  47             context.write(key, new IntWritable(sum));  48         }  49     }  50   51     public static void main(String[] args) throws Exception {  52         Configuration conf = new Configuration();  53         Job job = new Job(conf);  54         job.setJarByClass(WordCount.class);  55         job.setJobName("wordcount");  56   57         job.setOutputKeyClass(Text.class);  58         job.setOutputValueClass(IntWritable.class);  59   60         job.setMapperClass(WordCountMap.class);  61         job.setReducerClass(WordCountReduce.class);  62   63         job.setInputFormatClass(TextInputFormat.class);  64         job.setOutputFormatClass(TextOutputFormat.class);  65   66         FileInputFormat.addInputPath(job, new Path(args[0]));  67         FileOutputFormat.setOutputPath(job, new Path(args[1]));  68   69         job.waitForCompletion(true);  70     }  71 }
       
      
     

 

               [root@jediael conf]# hadoop fs -mkdir wcinput  [root@jediael conf]# hadoop fs -copyFromLocal * wcinput   [root@jediael conf]# hadoop fs -ls wcinput   Found 26 items   -rw-r--r-- 1 root supergroup 1524 2014-08-20 12:29 /user/root/wcinput/automaton-urlfilter.txt   -rw-r--r-- 1 root supergroup 1311 2014-08-20 12:29 /user/root/wcinput/configuration.xsl   -rw-r--r-- 1 root supergroup 131090 2014-08-20 12:29 /user/root/wcinput/domain-suffixes.xml   -rw-r--r-- 1 root supergroup 4649 2014-08-20 12:29 /user/root/wcinput/domain-suffixes.xsd   -rw-r--r-- 1 root supergroup 824 2014-08-20 12:29 /user/root/wcinput/domain-urlfilter.txt   -rw-r--r-- 1 root supergroup 3368 2014-08-20 12:29 /user/root/wcinput/gora-accumulo-mapping.xml   -rw-r--r-- 1 root supergroup 3279 2014-08-20 12:29 /user/root/wcinput/gora-cassandra-mapping.xml   -rw-r--r-- 1 root supergroup 3447 2014-08-20 12:29 /user/root/wcinput/gora-hbase-mapping.xml   -rw-r--r-- 1 root supergroup 2677 2014-08-20 12:29 /user/root/wcinput/gora-sql-mapping.xml   -rw-r--r-- 1 root supergroup 2993 2014-08-20 12:29 /user/root/wcinput/gora.properties   -rw-r--r-- 1 root supergroup 983 2014-08-20 12:29 /user/root/wcinput/hbase-site.xml   -rw-r--r-- 1 root supergroup 3096 2014-08-20 12:29 /user/root/wcinput/httpclient-auth.xml   -rw-r--r-- 1 root supergroup 3948 2014-08-20 12:29 /user/root/wcinput/log4j.properties   -rw-r--r-- 1 root supergroup 511 2014-08-20 12:29 /user/root/wcinput/nutch-conf.xsl   -rw-r--r-- 1 root supergroup 42610 2014-08-20 12:29 /user/root/wcinput/nutch-default.xml   -rw-r--r-- 1 root supergroup 753 2014-08-20 12:29 /user/root/wcinput/nutch-site.xml   -rw-r--r-- 1 root supergroup 347 2014-08-20 12:29 /user/root/wcinput/parse-plugins.dtd   -rw-r--r-- 1 root supergroup 3016 2014-08-20 12:29 /user/root/wcinput/parse-plugins.xml   -rw-r--r-- 1 root supergroup 857 2014-08-20 12:29 /user/root/wcinput/prefix-urlfilter.txt   -rw-r--r-- 1 root supergroup 2484 2014-08-20 12:29 /user/root/wcinput/regex-normalize.xml   -rw-r--r-- 1 root supergroup 1736 2014-08-20 12:29 /user/root/wcinput/regex-urlfilter.txt   -rw-r--r-- 1 root supergroup 18969 2014-08-20 12:29 /user/root/wcinput/schema-solr4.xml   -rw-r--r-- 1 root supergroup 6020 2014-08-20 12:29 /user/root/wcinput/schema.xml   -rw-r--r-- 1 root supergroup 1766 2014-08-20 12:29 /user/root/wcinput/solrindex-mapping.xml   -rw-r--r-- 1 root supergroup 1044 2014-08-20 12:29 /user/root/wcinput/subcollections.xml   -rw-r--r-- 1 root supergroup 1411 2014-08-20 12:29 /user/root/wcinput/suffix-urlfilter.txt
               root@jediael project]# hadoop fs -ls wcoutput3   Found 3 items   -rw-r--r-- 1 root supergroup 0 2014-08-20 12:52 /user/root/wcoutput3/_SUCCESS   drwxr-xr-x - root supergroup 0 2014-08-20 12:50 /user/root/wcoutput3/_logs   -rw-r--r-- 1 root supergroup 123950 2014-08-20 12:52 /user/root/wcoutput3/part-r-00000   [root@jediael project]# hadoop fs -cat wcoutput3/part-r-00000  !!      2  !ci.*.*.us      1  !co.*.*.us      1  !town.*.*.us    1  "AS     22  "Accept"        1  "Accept-Language"       1  "License");     22  "NOW"   1  "WiFi"  1  "Z"     1  "all"   1  "content"       1  "delete 1  "delimiter"     1