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    
019    package org.apache.hadoop.mapred;
020    
021    import java.io.IOException;
022    
023    import org.apache.hadoop.classification.InterfaceAudience;
024    import 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
037    public 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    }