org.apache.hadoop.mapreduce

类 OutputFormat<K,V>

java.lang.Object

org.apache.hadoop.mapreduce.OutputFormat<K,V>

直接已知子类:

DBOutputFormat, FileOutputFormat, FilterOutputFormat, NullOutputFormat

public abstract class OutputFormat<K,V>
extends Object

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.

另请参阅:

RecordWriter

构造器概要

构造器

构造器和说明
OutputFormat()

方法概要

方法

限定符和类型	方法和说明
abstract void	checkOutputSpecs(JobContext context) Check for validity of the output-specification for the job.
abstract OutputCommitter	getOutputCommitter(TaskAttemptContext context) Get the output committer for this output format.
abstract RecordWriter<K,V>	getRecordWriter(TaskAttemptContext context) Get the RecordWriter for the given task.

从类继承的方法 java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

构造器详细资料

OutputFormat

public OutputFormat()

方法详细资料

getRecordWriter

public abstract RecordWriter<K,V> getRecordWriter(TaskAttemptContext context)
                                           throws IOException,
                                                  InterruptedException

Get the RecordWriter for the given task.

参数:

context - the information about the current task.

返回:

a RecordWriter to write the output for the job.

抛出:

IOException

InterruptedException

checkOutputSpecs

public abstract void checkOutputSpecs(JobContext context)
                               throws IOException,
                                      InterruptedException

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.

参数:

context - information about the job

抛出:

IOException - when output should not be attempted

InterruptedException

getOutputCommitter

public abstract OutputCommitter getOutputCommitter(TaskAttemptContext context)
                                            throws IOException,
                                                   InterruptedException

Get the output committer for this output format. This is responsible for ensuring the output is committed correctly.

参数:

context - the task context

返回:

an output committer

抛出:

IOException

InterruptedException