View Javadoc

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 java.io.IOException;
22  
23  import org.apache.hadoop.classification.InterfaceAudience;
24  import org.apache.hadoop.classification.InterfaceStability;
25  import org.apache.hadoop.hbase.client.Result;
26  import org.apache.hadoop.hbase.client.Scan;
27  import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
28  import org.apache.hadoop.mapreduce.Job;
29  
30  /**
31   * Pass the given key and record as-is to the reduce phase.
32   */
33  @InterfaceAudience.Public
34  @InterfaceStability.Stable
35  public class IdentityTableMapper
36  extends TableMapper<ImmutableBytesWritable, Result> {
37  
38    /**
39     * Use this before submitting a TableMap job. It will appropriately set up
40     * the job.
41     *
42     * @param table  The table name.
43     * @param scan  The scan with the columns to scan.
44     * @param mapper  The mapper class.
45     * @param job  The job configuration.
46     * @throws IOException When setting up the job fails.
47     */
48    @SuppressWarnings("rawtypes")
49    public static void initJob(String table, Scan scan,
50      Class<? extends TableMapper> mapper, Job job) throws IOException {
51      TableMapReduceUtil.initTableMapperJob(table, scan, mapper,
52        ImmutableBytesWritable.class, Result.class, job);
53    }
54  
55    /**
56     * Pass the key, value to reduce.
57     *
58     * @param key  The current key.
59     * @param value  The current value.
60     * @param context  The current context.
61     * @throws IOException When writing the record fails.
62     * @throws InterruptedException When the job is aborted.
63     */
64    public void map(ImmutableBytesWritable key, Result value, Context context)
65    throws IOException, InterruptedException {
66      context.write(key, value);
67    }
68  
69  }