Class DelegatingMapper<K1,V1,K2,V2>

  extended by org.apache.hadoop.mapred.lib.DelegatingMapper<K1,V1,K2,V2>
All Implemented Interfaces:
Closeable, JobConfigurable, Mapper<K1,V1,K2,V2>

public class DelegatingMapper<K1,V1,K2,V2>
extends Object
implements Mapper<K1,V1,K2,V2>

An Mapper that delegates behaviour of paths to multiple other mappers.

See Also:
MultipleInputs.addInputPath(JobConf, Path, Class, Class)

Constructor Summary
Method Summary
 void close()
 void configure(JobConf conf)
          Initializes a new instance from a JobConf.
 void map(K1 key, V1 value, OutputCollector<K2,V2> outputCollector, Reporter reporter)
          Maps a single input key/value pair into an intermediate key/value pair.
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail


public DelegatingMapper()
Method Detail


public void map(K1 key,
                V1 value,
                OutputCollector<K2,V2> outputCollector,
                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<K1,V1,K2,V2>
key - the input key.
value - the input value.
outputCollector - collects mapped keys and values.
reporter - facility to report progress.


public void configure(JobConf conf)
Description copied from interface: JobConfigurable
Initializes a new instance from a JobConf.

Specified by:
configure in interface JobConfigurable
conf - the configuration


public void close()
           throws IOException
Specified by:
close in interface Closeable

Copyright © 2009 The Apache Software Foundation