/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.hadoop.mapreduce;
import java.io.IOException;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
/**
* A context object that allows input and output from the task. It is only
* supplied to the {@link Mapper} or {@link Reducer}.
* @param <KEYIN> the input key type for the task
* @param <VALUEIN> the input value type for the task
* @param <KEYOUT> the output key type for the task
* @param <VALUEOUT> the output value type for the task
*/
@InterfaceAudience.Public
@InterfaceStability.Evolving
public interface TaskInputOutputContext<KEYIN,VALUEIN,KEYOUT,VALUEOUT>
extends TaskAttemptContext {
/**
* Advance to the next key, value pair, returning null if at end.
* @return the key object that was read into, or null if no more
*/
public boolean nextKeyValue() throws IOException, InterruptedException;
/**
* Get the current key.
* @return the current key object or null if there isn't one
* @throws IOException
* @throws InterruptedException
*/
public KEYIN getCurrentKey() throws IOException, InterruptedException;
/**
* Get the current value.
* @return the value object that was read into
* @throws IOException
* @throws InterruptedException
*/
public VALUEIN getCurrentValue() throws IOException, InterruptedException;
/**
* Generate an output key/value pair.
*/
public void write(KEYOUT key, VALUEOUT value)
throws IOException, InterruptedException;
/**
* Get the {@link OutputCommitter} for the task-attempt.
* @return the <code>OutputCommitter</code> for the task-attempt
*/
public OutputCommitter getOutputCommitter();
}