1 /**
2 *
3 * Licensed to the Apache Software Foundation (ASF) under one
4 * or more contributor license agreements. See the NOTICE file
5 * distributed with this work for additional information
6 * regarding copyright ownership. The ASF licenses this file
7 * to you under the Apache License, Version 2.0 (the
8 * "License"); you may not use this file except in compliance
9 * with the License. You may obtain a copy of the License at
10 *
11 * http://www.apache.org/licenses/LICENSE-2.0
12 *
13 * Unless required by applicable law or agreed to in writing, software
14 * distributed under the License is distributed on an "AS IS" BASIS,
15 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16 * See the License for the specific language governing permissions and
17 * limitations under the License.
18 */
19 package org.apache.hadoop.hbase.mapreduce;
20
21 import org.apache.hadoop.hbase.classification.InterfaceAudience;
22 import org.apache.hadoop.hbase.classification.InterfaceStability;
23 import org.apache.hadoop.hbase.client.Mutation;
24 import org.apache.hadoop.mapreduce.Reducer;
25
26 /**
27 * Extends the basic <code>Reducer</code> class to add the required key and
28 * value input/output classes. While the input key and value as well as the
29 * output key can be anything handed in from the previous map phase the output
30 * value <u>must</u> be either a {@link org.apache.hadoop.hbase.client.Put Put}
31 * or a {@link org.apache.hadoop.hbase.client.Delete Delete} instance when
32 * using the {@link TableOutputFormat} class.
33 * <p>
34 * This class is extended by {@link IdentityTableReducer} but can also be
35 * subclassed to implement similar features or any custom code needed. It has
36 * the advantage to enforce the output value to a specific basic type.
37 *
38 * @param <KEYIN> The type of the input key.
39 * @param <VALUEIN> The type of the input value.
40 * @param <KEYOUT> The type of the output key.
41 * @see org.apache.hadoop.mapreduce.Reducer
42 */
43 @InterfaceAudience.Public
44 @InterfaceStability.Stable
45 public abstract class TableReducer<KEYIN, VALUEIN, KEYOUT>
46 extends Reducer<KEYIN, VALUEIN, KEYOUT, Mutation> {
47 }