hadoop - 较新 api 中 hadoop 中的 MultipleOutputs

Question

我写了一个简单的字数统计程序并试图得到输出
基于较新API格式的Multipleoutputs，我得到了输出
输出文件中的数据(带有键的名称):

import java.io.IOException; 
import java.util.StringTokenizer;

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.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper; 
import org.apache.hadoop.mapreduce.Mapper.Context; 
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.mapreduce.lib.output.MultipleOutputs;
import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;


public class word  {

    public static class wordmapper extends
        Mapper<LongWritable,Text,Text,IntWritable>  {

            Text x = new Text(); 
            IntWritable z =new IntWritable(1);
            String str1=null;

            public void map(LongWritable key, Text value,Context con)
                throws IOException, InterruptedException        {           

                StringTokenizer str = new StringTokenizer(value.toString());

                while(str.hasMoreTokens()) {
                    str1=str.nextToken();
                    x.set(str1);
                    con.write(x, z);            
                }

           }
    }


    public static class wordreducer extends Reducer<Text,
           IntWritable,Text, IntWritable>   {

           String generateFilename(Text k) { return k.toString(); }

           private MultipleOutputs mos;
           public void setup(Context context) { 
               mos =new MultipleOutputs(context);       
           }        

           String m=null;
           IntWritable num=new IntWritable(); 

           public void reduce(Text key,Iterable<IntWritable> value,Context con) 
               throws IOException, InterruptedException {

               int sum=0;
               for(IntWritable k :value) {
                   sum=sum+k.get();
               }
               num.set(sum);
               m=generateFilename(key);
               //mos.write(key, num, "text");
               //mos.write("text", key, num);
               mos.write("text", key, value, generateFilename(key));
               //con.write(key,num);
           }    
    }

    public static  void main(String args[]) 
        throws IOException, InterruptedException, ClassNotFoundException  {         

        Configuration con = new Configuration();        
        Job j= new Job(con,"word");
        j.setJarByClass(word.class);

        j.setMapperClass(wordmapper.class);
        j.setReducerClass(wordreducer.class);
        //j.setNumReduceTasks(0);

        j.setOutputKeyClass(Text.class);
        j.setOutputValueClass(IntWritable.class);

        MultipleOutputs.addNamedOutput(j,"text",TextOutputFormat.class,Text.class,IntWritable.class);

        //MultipleOutputs.addNamedOutput(j, namedOutput, outputFormatClass, keyClass, valueClass);

        FileInputFormat.addInputPath(j, new Path(args[0]));
        FileOutputFormat.setOutputPath(j, new Path(args[1]));

        System.exit(j.waitForCompletion(true)?0:1);     

    } 
}

我在文件中得到了输出，文件中没有任何数据，并且文件没有打开:

-rw-r--r--   1 root supergroup          0 2014-09-15 03:00 /user/root/listouput/world9/_SUCCESS 
drwxr-xr-x   - root supergroup          0 2014-09-15 03:00 /user/root/listouput/world9/_logs
-rw-r--r--   1 root supergroup          0 2014-09-15 03:00 /user/root/listouput/world9/best-r-00000
-rw-r--r--   1 root supergroup          0 2014-09-15 03:00 /user/root/listouput/world9/good-r-00000
-rw-r--r--   1 root supergroup          0 2014-09-15 03:00 /user/root/listouput/world9/hadoop-r-00000
-rw-r--r--   1 root supergroup          0 2014-09-15 03:00 /user/root/listouput/world9/hello-r-00000
-rw-r--r--   1 root supergroup          0 2014-09-15 03:00 /user/root/listouput/world9/is-r-00000
-rw-r--r--   1 root supergroup          0 2014-09-15 03:00 /user/root/listouput/world9/part-r-00000
-rw-r--r--   1 root supergroup          0 2014-09-15 03:00 /user/root/listouput/world9/rule-r-00000
-rw-r--r--   1 root supergroup          0 2014-09-15 03:00 /user/root/listouput/world9/the-r-00000
-rw-r--r--   1 root supergroup          0 2014-09-15 03:00 /user/root/listouput/world9/we-r-00000
-rw-r--r--   1 root supergroup          0 2014-09-15 03:00 /user/root/listouput/world9/world-r-00000
root@ubuntu:/home/mrinmoy/Desktop/PracticeJar files# hadoop fs -cat
/user/root/listouput/world9/best-r-00000

Answer 1

输出文件为空，因为您忘记关闭 mos ，您需要覆盖 cleanup你的 reducer 的方法:

@Override
protected void cleanup(Context context) throws IOException, InterruptedException {
    mos.close();
}