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 */
018package org.apache.hadoop.hbase.mapreduce;
019
020import org.apache.hadoop.hbase.client.Mutation;
021import org.apache.hadoop.mapreduce.Reducer;
022import org.apache.yetus.audience.InterfaceAudience;
023
024/**
025 * Extends the basic <code>Reducer</code> class to add the required key and value input/output
026 * classes. While the input key and value as well as the output key can be anything handed in from
027 * the previous map phase the output value <u>must</u> be either a
028 * {@link org.apache.hadoop.hbase.client.Put Put} or a {@link org.apache.hadoop.hbase.client.Delete
029 * Delete} instance when using the {@link TableOutputFormat} class.
030 * <p>
031 * This class is extended by {@link IdentityTableReducer} but can also be subclassed to implement
032 * similar features or any custom code needed. It has the advantage to enforce the output value to a
033 * specific basic type.
034 * @param <KEYIN>   The type of the input key.
035 * @param <VALUEIN> The type of the input value.
036 * @param <KEYOUT>  The type of the output key.
037 * @see org.apache.hadoop.mapreduce.Reducer
038 */
039@InterfaceAudience.Public
040public abstract class TableReducer<KEYIN, VALUEIN, KEYOUT>
041  extends Reducer<KEYIN, VALUEIN, KEYOUT, Mutation> {
042}