org.apache.hadoop.mapred
Interface Mapper

All Superinterfaces:

Closeable, JobConfigurable

All Known Implementing Classes:

CopyFiles.FSCopyFilesMapper, CopyFiles.HTTPCopyFilesMapper, DataJoinMapperBase, DataJoinReducerBase, FieldSelectionMapReduce, IdentityMapper, InverseMapper, JobBase, Logalyzer.LogRegexMapper, PiEstimator.PiMapper, PipeMapper, RegexMapper, TokenCountMapper, ValueAggregatorCombiner, ValueAggregatorJobBase, ValueAggregatorMapper, ValueAggregatorReducer, WordCount.MapClass

public interface Mapper
extends JobConfigurable, Closeable

Maps input key/value pairs to a set of intermediate key/value pairs. All intermediate values associated with a given output key are subsequently grouped by the map/reduce system, and passed to a Reducer to determine the final output..

Method Summary

void	map(WritableComparable key, Writable value, OutputCollector output, Reporter reporter) Maps a single input key/value pair into intermediate key/value pairs.

Methods inherited from interface org.apache.hadoop.mapred.JobConfigurable

configure

Methods inherited from interface org.apache.hadoop.io.Closeable

close

Method Detail

map

void map(WritableComparable key,
         Writable value,
         OutputCollector output,
         Reporter reporter)
         throws IOException

Maps a single input key/value pair into intermediate key/value pairs. 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(WritableComparable,Writable).

Parameters:

key - the key

value - the values

output - collects mapped keys and values

Throws:

IOException