Class TokenCountMapper<K>

  extended by org.apache.hadoop.mapred.MapReduceBase
      extended by org.apache.hadoop.mapred.lib.TokenCountMapper<K>
All Implemented Interfaces:
Closeable, JobConfigurable, Mapper<K,Text,Text,LongWritable>

public class TokenCountMapper<K>
extends MapReduceBase
implements Mapper<K,Text,Text,LongWritable>

A Mapper that maps text values into pairs. Uses StringTokenizer to break text into tokens.

Constructor Summary
Method Summary
 void map(K key, Text value, OutputCollector<Text,LongWritable> output, Reporter reporter)
          Maps a single input key/value pair into an intermediate key/value pair.
Methods inherited from class org.apache.hadoop.mapred.MapReduceBase
close, configure
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
Methods inherited from interface org.apache.hadoop.mapred.JobConfigurable
Methods inherited from interface

Constructor Detail


public TokenCountMapper()
Method Detail


public void map(K key,
                Text value,
                OutputCollector<Text,LongWritable> output,
                Reporter reporter)
         throws IOException
Description copied from interface: Mapper
Maps a single input key/value pair into an intermediate key/value pair.

Output pairs need not be of the same types as input pairs. A given input pair may map to zero or many output pairs. Output pairs are collected with calls to OutputCollector.collect(Object,Object).

Applications can use the Reporter provided to report progress or just indicate that they are alive. In scenarios where the application takes an insignificant amount of time to process individual key/value pairs, this is crucial since the framework might assume that the task has timed-out and kill that task. The other way of avoiding this is to set mapred.task.timeout to a high-enough value (or even zero for no time-outs).

Specified by:
map in interface Mapper<K,Text,Text,LongWritable>
key - the input key.
value - the input value.
output - collects mapped keys and values.
reporter - facility to report progress.

Copyright © 2009 The Apache Software Foundation