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.lib; 020 021 import java.io.IOException; 022 023 import org.apache.hadoop.classification.InterfaceAudience; 024 import org.apache.hadoop.classification.InterfaceStability; 025 import org.apache.hadoop.mapred.Mapper; 026 import org.apache.hadoop.mapred.OutputCollector; 027 import org.apache.hadoop.mapred.Reporter; 028 import org.apache.hadoop.mapred.MapReduceBase; 029 030 /** 031 * Implements the identity function, mapping inputs directly to outputs. 032 */ 033 @InterfaceAudience.Public 034 @InterfaceStability.Stable 035 public class IdentityMapper<K, V> 036 extends MapReduceBase implements Mapper<K, V, K, V> { 037 038 /** The identify function. Input key/value pair is written directly to 039 * output.*/ 040 public void map(K key, V val, 041 OutputCollector<K, V> output, Reporter reporter) 042 throws IOException { 043 output.collect(key, val); 044 } 045 }