org.apache.hadoop.mapred.lib
Class DelegatingMapper<K1,V1,K2,V2>

java.lang.Object
  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

DelegatingMapper()

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

DelegatingMapper

public DelegatingMapper()

Method Detail

map

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>

Parameters:

key - the input key.

value - the input value.

outputCollector - collects mapped keys and values.

reporter - facility to report progress.

Throws:

IOException

configure

public void configure(JobConf conf)

Description copied from interface: JobConfigurable

Initializes a new instance from a JobConf.

Specified by:

configure in interface JobConfigurable

Parameters:

conf - the configuration

close

public void close()
           throws IOException

Specified by:

close in interface Closeable

Throws:

IOException