org.apache.hadoop.mapreduce

类 RecordReader<KEYIN,VALUEIN>

java.lang.Object

org.apache.hadoop.mapreduce.RecordReader<KEYIN,VALUEIN>

类型参数:

KEYIN -

VALUEIN -

所有已实现的接口:

Closeable, AutoCloseable

直接已知子类:

CombineFileRecordReader, DBRecordReader, DelegatingRecordReader, DynamicRecordReader, KeyValueLineRecordReader, LineRecordReader, SequenceFileAsBinaryInputFormat.SequenceFileAsBinaryRecordReader, SequenceFileAsTextRecordReader, SequenceFileRecordReader

public abstract class RecordReader<KEYIN,VALUEIN>
extends Object
implements Closeable

The record reader breaks the data into key/value pairs for input to the Mapper.

构造器概要

构造器

构造器和说明
RecordReader()

方法概要

方法

限定符和类型	方法和说明
abstract void	close() Close the record reader.
abstract KEYIN	getCurrentKey() Get the current key
abstract VALUEIN	getCurrentValue() Get the current value.
abstract float	getProgress() The current progress of the record reader through its data.
abstract void	initialize(InputSplit split, TaskAttemptContext context) Called once at initialization.
abstract boolean	nextKeyValue() Read the next key, value pair.

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

RecordReader

public RecordReader()

方法详细资料

initialize

public abstract void initialize(InputSplit split,
              TaskAttemptContext context)
                         throws IOException,
                                InterruptedException

Called once at initialization.

参数:

split - the split that defines the range of records to read

context - the information about the task

抛出:

IOException

InterruptedException

nextKeyValue

public abstract boolean nextKeyValue()
                              throws IOException,
                                     InterruptedException

Read the next key, value pair.

返回:

true if a key/value pair was read

抛出:

IOException

InterruptedException

getCurrentKey

public abstract KEYIN getCurrentKey()
                             throws IOException,
                                    InterruptedException

Get the current key

返回:

the current key or null if there is no current key

抛出:

IOException

InterruptedException

getCurrentValue

public abstract VALUEIN getCurrentValue()
                                 throws IOException,
                                        InterruptedException

Get the current value.

返回:

the object that was read

抛出:

IOException

InterruptedException

getProgress

public abstract float getProgress()
                           throws IOException,
                                  InterruptedException

The current progress of the record reader through its data.

返回:

a number between 0.0 and 1.0 that is the fraction of the data read

抛出:

IOException

InterruptedException

close

public abstract void close()
                    throws IOException

Close the record reader.

指定者:

close 在接口中 Closeable

指定者:

close 在接口中 AutoCloseable

抛出:

IOException