MapReduce编程：数字排序

问题描述

将乱序数字按照升序排序。
思路描述

按照mapreduce的默认排序，依次输出key值。
代码

 1 package org.apache.hadoop.examples;
 2 
 3 import java.io.IOException;
 4 import java.util.Iterator;
 5 import java.util.StringTokenizer;
 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.Text;
10 import org.apache.hadoop.mapreduce.Job;
11 import org.apache.hadoop.mapreduce.Mapper;
12 import org.apache.hadoop.mapreduce.Reducer;
13 import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
14 import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
15  
16 public class sort {
17     public sort() {
18     }
19  
20     public static void main(String[] args) throws Exception {
21         Configuration conf = new Configuration();
22         
23         String fileAddress = "hdfs://localhost:9000/user/hadoop/";
24         
25         //String[] otherArgs = (new GenericOptionsParser(conf, args)).getRemainingArgs();
26         String[] otherArgs = new String[]{fileAddress+"number.txt", fileAddress+"output"};
27         if(otherArgs.length < 2) {
28             System.err.println("Usage: sort <in> [<in>...] <out>");
29             System.exit(2);
30         }
31  
32         Job job = Job.getInstance(conf, "sort");
33         job.setJarByClass(sort.class);
34         job.setMapperClass(sort.TokenizerMapper.class);
35         //job.setCombinerClass(sort.SortReducer.class);
36         job.setReducerClass(sort.SortReducer.class);
37         job.setOutputKeyClass(IntWritable.class);
38         job.setOutputValueClass(IntWritable.class);
39  
40         for(int i = 0; i < otherArgs.length - 1; ++i) {
41             FileInputFormat.addInputPath(job, new Path(otherArgs[i]));
42         }
43  
44         FileOutputFormat.setOutputPath(job, new Path(otherArgs[otherArgs.length - 1]));
45         System.exit(job.waitForCompletion(true)?0:1);
46     }
47     
48     
49     public static class TokenizerMapper extends Mapper<Object, Text, IntWritable, IntWritable> {
50          
51         public TokenizerMapper() {
52         }
53  
54         public void map(Object key, Text value, Context context) throws IOException, InterruptedException {
55             StringTokenizer itr = new StringTokenizer(value.toString());
56  
57             while(itr.hasMoreTokens()) {
58                 context.write(new IntWritable(Integer.parseInt(itr.nextToken())), new IntWritable(1));
59             }
60  
61         }
62     }
63  
64     
65     public static class SortReducer extends Reducer<IntWritable, IntWritable, IntWritable, IntWritable> {
66  
67         private static IntWritable num = new IntWritable(1);
68         
69         public SortReducer() {
70         }
71  
72         public void reduce(IntWritable key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException {
73             
74             for(Iterator<IntWritable> i$ = values.iterator(); i$.hasNext();i$.next()) {
75                 context.write(num, key);
76             }
77            num = new IntWritable(num.get()+1);
78         }
79     }
80  
81 }
注：不能有combiner操作。
不然就会变成