Interface OutputFormat<K,V>

All Known Implementing Classes:
DBOutputFormat, FileOutputFormat, IndexUpdateOutputFormat, MapFileOutputFormat, MultipleOutputFormat, MultipleSequenceFileOutputFormat, MultipleTextOutputFormat, NullOutputFormat, SequenceFileAsBinaryOutputFormat, SequenceFileOutputFormat, TeraOutputFormat, TextOutputFormat

public interface OutputFormat<K,V>

OutputFormat describes the output-specification for a Map-Reduce job.

The Map-Reduce framework relies on the OutputFormat of the job to:

  1. Validate the output-specification of the job. For e.g. check that the output directory doesn't already exist.
  2. Provide the RecordWriter implementation to be used to write out the output files of the job. Output files are stored in a FileSystem.

See Also:
RecordWriter, JobConf

Method Summary
 void checkOutputSpecs(FileSystem ignored, JobConf job)
          Check for validity of the output-specification for the job.
 RecordWriter<K,V> getRecordWriter(FileSystem ignored, JobConf job, String name, Progressable progress)
          Get the RecordWriter for the given job.

Method Detail


RecordWriter<K,V> getRecordWriter(FileSystem ignored,
                                  JobConf job,
                                  String name,
                                  Progressable progress)
                                  throws IOException
Get the RecordWriter for the given job.

ignored -
job - configuration for the job whose output is being written.
name - the unique name for this part of the output.
progress - mechanism for reporting progress while writing to file.
a RecordWriter to write the output for the job.


void checkOutputSpecs(FileSystem ignored,
                      JobConf job)
                      throws IOException
Check for validity of the output-specification for the job.

This is to validate the output specification for the job when it is a job is submitted. Typically checks that it does not already exist, throwing an exception when it already exists, so that output is not overwritten.

ignored -
job - job configuration.
IOException - when output should not be attempted

Copyright © 2009 The Apache Software Foundation