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 */
018
019package org.apache.hadoop.mapreduce.lib.map;
020
021import java.io.IOException;
022import java.util.regex.Matcher;
023import java.util.regex.Pattern;
024
025import org.apache.hadoop.classification.InterfaceAudience;
026import org.apache.hadoop.classification.InterfaceStability;
027import org.apache.hadoop.conf.Configuration;
028import org.apache.hadoop.io.LongWritable;
029import org.apache.hadoop.io.Text;
030import org.apache.hadoop.mapreduce.Mapper;
031
032
033/** A {@link Mapper} that extracts text matching a regular expression. */
034@InterfaceAudience.Public
035@InterfaceStability.Stable
036public class RegexMapper<K> extends Mapper<K, Text, Text, LongWritable> {
037
038  public static String PATTERN = "mapreduce.mapper.regex";
039  public static String GROUP = "mapreduce.mapper.regexmapper..group";
040  private Pattern pattern;
041  private int group;
042
043  public void setup(Context context) {
044    Configuration conf = context.getConfiguration();
045    pattern = Pattern.compile(conf.get(PATTERN));
046    group = conf.getInt(GROUP, 0);
047  }
048
049  public void map(K key, Text value,
050                  Context context)
051    throws IOException, InterruptedException {
052    String text = value.toString();
053    Matcher matcher = pattern.matcher(text);
054    while (matcher.find()) {
055      context.write(new Text(matcher.group(group)), new LongWritable(1));
056    }
057  }
058}