Question

我正在尝试使用Hadoop mapReduce对输入的数据进行排序。问题是我只能按键对键值对进行排序，而我试图按值对它们进行排序。每个值的键都是用一个计数器创建的，所以第一个值（234）具有键1，第二个值（944）具有键2，依此类推。关于如何操作并按值对输入进行排序的任何想法吗？ >


import java.io.IOException;
import java.util.StringTokenizer;
import java.util.ArrayList;
import java.util.List;
import java.util.Collections;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

public class Sortt {

  public static class TokenizerMapper
       extends Mapper<Object, Text, Text ,IntWritable >{
    int k=0;
    int v=0;
    int va=0;
    public Text ke = new Text();
   private final static IntWritable val = new IntWritable();

    public void map(Object key, Text value, Context context) throws 
    IOException, InterruptedException 
{
      StringTokenizer itr = new StringTokenizer(value.toString());


        while (itr.hasMoreTokens()) 
{
        val.set(Integer.parseInt(itr.nextToken()));
        v=val.get();
        k=k+1;
        ke.set(Integer.toString(k));

        context.write(ke, new IntWritable(v));}
}


    }


  public static class SortReducer
       extends Reducer<Text,IntWritable,Text,IntWritable> {
        int a=0;
        int v=0;
       private IntWritable va = new IntWritable();
    public void reduce(Text key, Iterable<IntWritable> values,
                       Context context
                       ) throws IOException, InterruptedException {
    List<Integer> sorted = new ArrayList<Integer>();

    for (IntWritable val : values) {
           a= val.get();
          sorted.add(a);

}
    Collections.sort(sorted);
    for(int i=0;i<sorted.size();i++) {
    v=sorted.get(i);
    va.set(v);

     context.write(key, va);
}
    }
  }

  public static void main(String[] args) throws Exception {
   long startTime=0;
   long Time=0;
   long duration=0;
Configuration conf = new Configuration();
    Job job = Job.getInstance(conf, "sort");
    job.setJarByClass(Sortt.class);
    job.setMapperClass(TokenizerMapper.class);
    job.setCombinerClass(SortReducer.class);
    job.setReducerClass(SortReducer.class);
    job.setOutputKeyClass(Text.class);
    job.setOutputValueClass(IntWritable.class);
    FileInputFormat.addInputPath(job, new Path(args[0]));
    FileOutputFormat.setOutputPath(job, new Path(args[1]));
    System.exit(job.waitForCompletion(true) ? 0 : 1);
    Time = System.currentTimeMillis();
  //duration = (endTime-startTime)/1000000;
    System.out.println("time="+Time+"MS");
  }
}

输入：

234

944

241

130

369

470

250

100

250

735

856

659

425

756

123

756

459

754

654

951

753

254

698

741

预期输出：

8100

15 123

4130

1 234

3 241

24 241

7 250

9250

22 254

5 369

13425

17 459

6 470

19 654

12 659

23698

10 735

21 753

18 754

14 756

16 756

11 856

2 944

20 951

当前输出：