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## org.apache.hadoop.mapreduce
Class TaskInputOutputContext<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>

Type Parameters:
  `KEYIN` - the input key type for the task
  `VALUEIN` - the input value type for the task
  `KEYOUT` - the output key type for the task
  `VALUEOUT` - the output value type for the task

All Implemented Interfaces:
  Progressable

Direct Known Subclasses:
  MapContext, ReduceContext

    public abstract class TaskInputOutputContext<KEYIN,VALUEIN,KEYOUT,VALUEOUT>

extends TaskAttemptContext
implements Progressable

A context object that allows input and output from the task. It is only supplied to the `Mapper` or `Reducer`.

Field Summary

Fields inherited from class 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`

Constructor Summary
`TaskInputOutputContext(Configuration conf, TaskAttemptID taskid, RecordWriter<KEYOUT,VALUEOUT> output, OutputCommitter committer, StatusReporter reporter)`

Method Summary
`Counter` | `getCounter(Enum<?> counterName)`
`Counter` | `getCounter(String groupName, String counterName)`
`abstract KEYIN` | `getCurrentKey()` Get the current key.
`abstract VALUEIN` | `getCurrentValue()` Get the current value.
`OutputCommitter` | `getOutputCommitter()`
`abstract boolean` | `nextKeyValue()` Advance to the next key, value pair, returning null if at end.
`void` | `progress()` Report progress.
`void` | `setStatus(String status)` Set the current status of the task to the given string.
`void` | `write(KEYOUT key, VALUEOUT value)` Generate an output key/value pair.

Methods inherited from class org.apache.hadoop.mapreduce.TaskAttemptContext
`getStatus, getTaskAttemptID`

Methods inherited from class org.apache.hadoop.mapreduce.JobContext
`getCombinerClass, getConfiguration, getCredentials, getGroupingComparator, getInputFormatClass, getJar, getJobID, getJobName, getMapOutputKeyClass, getMapOutputValueClass, getMapperClass, getNumReduceTasks, getOutputFormatClass, getOutputKeyClass, getOutputValueClass, getPartitionerClass, getReducerClass, getSortComparator, getWorkingDirectory`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### TaskInputOutputContext

    public TaskInputOutputContext(Configuration conf,
                                  TaskAttemptID taskid,
                                  RecordWriter<KEYOUT,VALUEOUT> output,
                                  OutputCommitter committer,
                                  StatusReporter reporter)

Method Detail

### nextKeyValue

    public abstract boolean nextKeyValue()
                                  throws IOException,
                                         InterruptedException

  Advance to the next key, value pair, returning null if at end.

  Returns:
    the key object that was read into, or null if no more
  Throws:
    `IOException`
    `InterruptedException`

### getCurrentKey

    public abstract KEYIN getCurrentKey()
                                 throws IOException,
                                        InterruptedException

  Get the current key.

  Returns:
    the current key object or null if there isn't one
  Throws:
    `IOException`
    `InterruptedException`

### getCurrentValue

    public abstract VALUEIN getCurrentValue()
                                     throws IOException,
                                            InterruptedException

  Get the current value.

  Returns:
    the value object that was read into
  Throws:
    `IOException`
    `InterruptedException`

### write

    public void write(KEYOUT key,
                      VALUEOUT value)
               throws IOException,
                      InterruptedException

  Generate an output key/value pair.

  Throws:
    `IOException`
    `InterruptedException`

### getCounter

    public Counter getCounter(Enum<?> counterName)

### getCounter

    public Counter getCounter(String groupName,
                              String counterName)

### progress

    public void progress()

  Description copied from class: `TaskAttemptContext`
  Report progress. The subtypes actually do work in this method.

  Specified by:
    `progress` in interface `Progressable`
  Overrides:
    `progress` in class `TaskAttemptContext`

### setStatus

    public void setStatus(String status)

  Description copied from class: `TaskAttemptContext`
  Set the current status of the task to the given string.

  Overrides:
    `setStatus` in class `TaskAttemptContext`

### getOutputCommitter

    public OutputCommitter getOutputCommitter()

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Copyright © 2009 The Apache Software Foundation