hbase-server/src/main/java/org/apache/hadoop/hbase/mapreduce/IdentityTableMapper.java

/**
 *
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.hadoop.hbase.mapreduce;

import java.io.IOException;

import org.apache.hadoop.hbase.classification.InterfaceAudience;
import org.apache.hadoop.hbase.classification.InterfaceStability;
import org.apache.hadoop.hbase.client.Result;
import org.apache.hadoop.hbase.client.Scan;
import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
import org.apache.hadoop.mapreduce.Job;

/**
 * Pass the given key and record as-is to the reduce phase.
 */
@InterfaceAudience.Public
@InterfaceStability.Stable
public class IdentityTableMapper
extends TableMapper<ImmutableBytesWritable, Result> {

  /**
   * Use this before submitting a TableMap job. It will appropriately set up
   * the job.
   *
   * @param table  The table name.
   * @param scan  The scan with the columns to scan.
   * @param mapper  The mapper class.
   * @param job  The job configuration.
   * @throws IOException When setting up the job fails.
   */
  @SuppressWarnings("rawtypes")
  public static void initJob(String table, Scan scan,
    Class<? extends TableMapper> mapper, Job job) throws IOException {
    TableMapReduceUtil.initTableMapperJob(table, scan, mapper,
      ImmutableBytesWritable.class, Result.class, job);
  }

  /**
   * Pass the key, value to reduce.
   *
   * @param key  The current key.
   * @param value  The current value.
   * @param context  The current context.
   * @throws IOException When writing the record fails.
   * @throws InterruptedException When the job is aborted.
   */
  public void map(ImmutableBytesWritable key, Result value, Context context)
  throws IOException, InterruptedException {
    context.write(key, value);
  }

}