org.apache.hadoop.mapreduce

类 ReduceContext<KEYIN,VALUEIN,KEYOUT,VALUEOUT>

java.lang.Object

org.apache.hadoop.mapreduce.JobContext

org.apache.hadoop.mapreduce.TaskAttemptContext

org.apache.hadoop.mapreduce.TaskInputOutputContext<KEYIN,VALUEIN,KEYOUT,VALUEOUT>

org.apache.hadoop.mapreduce.ReduceContext<KEYIN,VALUEIN,KEYOUT,VALUEOUT>

类型参数:

KEYIN - the class of the input keys

VALUEIN - the class of the input values

KEYOUT - the class of the output keys

VALUEOUT - the class of the output values

所有已实现的接口:

Progressable

直接已知子类:

Reducer.Context

public class ReduceContext<KEYIN,VALUEIN,KEYOUT,VALUEOUT>
extends TaskInputOutputContext<KEYIN,VALUEIN,KEYOUT,VALUEOUT>

The context passed to the Reducer.

嵌套类概要

嵌套类

限定符和类型	类和说明
protected class	ReduceContext.ValueIterable
protected class	ReduceContext.ValueIterator

字段概要

字段

限定符和类型	字段和说明
protected Progressable	reporter

从类继承的字段 org.apache.hadoop.mapreduce.JobContext

CACHE_ARCHIVES_VISIBILITIES, CACHE_FILE_VISIBILITIES, COMBINE_CLASS_ATTR, conf, credentials, INPUT_FORMAT_CLASS_ATTR, JOB_ACL_MODIFY_JOB, JOB_ACL_VIEW_JOB, JOB_CANCEL_DELEGATION_TOKEN, JOB_NAMENODES, MAP_CLASS_ATTR, OUTPUT_FORMAT_CLASS_ATTR, PARTITIONER_CLASS_ATTR, REDUCE_CLASS_ATTR, ugi, USER_LOG_RETAIN_HOURS

构造器概要

构造器

构造器和说明
ReduceContext(Configuration conf, TaskAttemptID taskid, RawKeyValueIterator input, Counter inputKeyCounter, Counter inputValueCounter, RecordWriter<KEYOUT,VALUEOUT> output, OutputCommitter committer, StatusReporter reporter, RawComparator<KEYIN> comparator, Class<KEYIN> keyClass, Class<VALUEIN> valueClass)

方法概要

方法

限定符和类型	方法和说明
KEYIN	getCurrentKey() Get the current key.
VALUEIN	getCurrentValue() Get the current value.
Iterable<VALUEIN>	getValues() Iterate through the values for the current key, reusing the same value object, which is stored in the context.
boolean	nextKey() Start processing next unique key.
boolean	nextKeyValue() Advance to the next key/value pair.

从类继承的方法 org.apache.hadoop.mapreduce.TaskInputOutputContext

getCounter, getCounter, getOutputCommitter, getProgress, progress, setStatus, write

从类继承的方法 org.apache.hadoop.mapreduce.TaskAttemptContext

getStatus, getTaskAttemptID

从类继承的方法 org.apache.hadoop.mapreduce.JobContext

getCombinerClass, getConfiguration, getCredentials, getGroupingComparator, getInputFormatClass, getJar, getJobID, getJobName, getMapOutputKeyClass, getMapOutputValueClass, getMapperClass, getNumReduceTasks, getOutputFormatClass, getOutputKeyClass, getOutputValueClass, getPartitionerClass, getReducerClass, getSortComparator, getWorkingDirectory

从类继承的方法 java.lang.Object

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

字段详细资料

reporter

protected Progressable reporter

构造器详细资料

ReduceContext

public ReduceContext(Configuration conf,
             TaskAttemptID taskid,
             RawKeyValueIterator input,
             Counter inputKeyCounter,
             Counter inputValueCounter,
             RecordWriter<KEYOUT,VALUEOUT> output,
             OutputCommitter committer,
             StatusReporter reporter,
             RawComparator<KEYIN> comparator,
             Class<KEYIN> keyClass,
             Class<VALUEIN> valueClass)
              throws InterruptedException,
                     IOException

抛出:

InterruptedException

IOException

方法详细资料

nextKey

public boolean nextKey()
                throws IOException,
                       InterruptedException

Start processing next unique key.

抛出:

IOException

InterruptedException

nextKeyValue

public boolean nextKeyValue()
                     throws IOException,
                            InterruptedException

Advance to the next key/value pair.

指定者:

nextKeyValue 在类中 TaskInputOutputContext<KEYIN,VALUEIN,KEYOUT,VALUEOUT>

返回:

the key object that was read into, or null if no more

抛出:

IOException

InterruptedException

getCurrentKey

public KEYIN getCurrentKey()

从类复制的说明: TaskInputOutputContext

Get the current key.

指定者:

getCurrentKey 在类中 TaskInputOutputContext<KEYIN,VALUEIN,KEYOUT,VALUEOUT>

返回:

the current key object or null if there isn't one

getCurrentValue

public VALUEIN getCurrentValue()

从类复制的说明: TaskInputOutputContext

Get the current value.

指定者:

getCurrentValue 在类中 TaskInputOutputContext<KEYIN,VALUEIN,KEYOUT,VALUEOUT>

返回:

the value object that was read into

getValues

public Iterable<VALUEIN> getValues()
                            throws IOException,
                                   InterruptedException

Iterate through the values for the current key, reusing the same value object, which is stored in the context.

返回:

the series of values associated with the current key. All of the objects returned directly and indirectly from this method are reused.

抛出:

IOException

InterruptedException