1 /** 2 * Copyright 2007 The Apache Software Foundation 3 * 4 * Licensed to the Apache Software Foundation (ASF) under one 5 * or more contributor license agreements. See the NOTICE file 6 * distributed with this work for additional information 7 * regarding copyright ownership. The ASF licenses this file 8 * to you under the Apache License, Version 2.0 (the 9 * "License"); you may not use this file except in compliance 10 * with the License. You may obtain a copy of the License at 11 * 12 * http://www.apache.org/licenses/LICENSE-2.0 13 * 14 * Unless required by applicable law or agreed to in writing, software 15 * distributed under the License is distributed on an "AS IS" BASIS, 16 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 17 * See the License for the specific language governing permissions and 18 * limitations under the License. 19 */ 20 package org.apache.hadoop.hbase.mapreduce; 21 22 import org.apache.hadoop.io.Writable; 23 import org.apache.hadoop.mapreduce.Reducer; 24 25 /** 26 * Extends the basic <code>Reducer</code> class to add the required key and 27 * value input/output classes. While the input key and value as well as the 28 * output key can be anything handed in from the previous map phase the output 29 * value <u>must</u> be either a {@link org.apache.hadoop.hbase.client.Put Put} 30 * or a {@link org.apache.hadoop.hbase.client.Delete Delete} instance when 31 * using the {@link TableOutputFormat} class. 32 * <p> 33 * This class is extended by {@link IdentityTableReducer} but can also be 34 * subclassed to implement similar features or any custom code needed. It has 35 * the advantage to enforce the output value to a specific basic type. 36 * 37 * @param <KEYIN> The type of the input key. 38 * @param <VALUEIN> The type of the input value. 39 * @param <KEYOUT> The type of the output key. 40 * @see org.apache.hadoop.mapreduce.Reducer 41 */ 42 public abstract class TableReducer<KEYIN, VALUEIN, KEYOUT> 43 extends Reducer<KEYIN, VALUEIN, KEYOUT, Writable> { 44 }