public class RecordMapper
extends Object

This takes data from a specified RecordReader and writes the data out with the specified RecordWriter. The setup is as follows: Specify a RecordReader as the data source Specify a RecordWriter as the destination. When setting up the locations, use 2 different InputSplit callling RecordWriter.initialize(InputSplit, Partitioner) and RecordReader.initialize(InputSplit) respectively to configure the locations of where the data will be read from and written to. When writing the data, you need to specify a link Partitioner to determine how to slice up the data being written (say in to number of lines per record per file per NumberOfRecordsPartitioner among other implementations. Finally, you may specify a batch size for batch read and write if the record reader and writer support it. Of note, is you can also specify multiple readers. In which case, it will read from every stream jointly and write out the specified writer accordingly. copy() will work the same with the following exceptions, you must specify splitPerReader (one split per reader) readersToConcat and the readers which will be read from writing to the same record writer. See copy() for more information here.