001/**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018
019package org.apache.hadoop.mapred;
020
021import java.io.IOException;
022
023import org.apache.hadoop.classification.InterfaceAudience;
024import org.apache.hadoop.classification.InterfaceStability;
025
026/**
027 * Collects the <code>&lt;key, value&gt;</code> pairs output by {@link Mapper}s
028 * and {@link Reducer}s.
029 *  
030 * <p><code>OutputCollector</code> is the generalization of the facility 
031 * provided by the Map-Reduce framework to collect data output by either the 
032 * <code>Mapper</code> or the <code>Reducer</code> i.e. intermediate outputs 
033 * or the output of the job.</p>  
034 */
035@InterfaceAudience.Public
036@InterfaceStability.Stable
037public interface OutputCollector<K, V> {
038  
039  /** Adds a key/value pair to the output.
040   *
041   * @param key the key to collect.
042   * @param value to value to collect.
043   * @throws IOException
044   */
045  void collect(K key, V value) throws IOException;
046}