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.mapreduce.lib.map; 020 021import java.io.IOException; 022 023import org.apache.hadoop.classification.InterfaceAudience; 024import org.apache.hadoop.classification.InterfaceStability; 025import org.apache.hadoop.mapreduce.Mapper; 026 027/** A {@link Mapper} that swaps keys and values. */ 028@InterfaceAudience.Public 029@InterfaceStability.Stable 030public class InverseMapper<K, V> extends Mapper<K,V,V,K> { 031 032 /** The inverse function. Input keys and values are swapped.*/ 033 @Override 034 public void map(K key, V value, Context context 035 ) throws IOException, InterruptedException { 036 context.write(value, key); 037 } 038 039}