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.mapred.lib;
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.io.LongWritable;
028import org.apache.hadoop.io.Text;
029import org.apache.hadoop.mapred.JobConf;
030import org.apache.hadoop.mapred.MapReduceBase;
031import org.apache.hadoop.mapred.Mapper;
032import org.apache.hadoop.mapred.OutputCollector;
033import org.apache.hadoop.mapred.Reporter;
034
035
036/** 
037 * A {@link Mapper} that extracts text matching a regular expression.
038 */
039@InterfaceAudience.Public
040@InterfaceStability.Stable
041public class RegexMapper<K> extends MapReduceBase
042    implements Mapper<K, Text, Text, LongWritable> {
043
044  private Pattern pattern;
045  private int group;
046
047  public void configure(JobConf job) {
048    pattern = Pattern.compile(job.get(org.apache.hadoop.mapreduce.lib.map.
049                RegexMapper.PATTERN));
050    group = job.getInt(org.apache.hadoop.mapreduce.lib.map.
051              RegexMapper.GROUP, 0);
052  }
053
054  public void map(K key, Text value,
055                  OutputCollector<Text, LongWritable> output,
056                  Reporter reporter)
057    throws IOException {
058    String text = value.toString();
059    Matcher matcher = pattern.matcher(text);
060    while (matcher.find()) {
061      output.collect(new Text(matcher.group(group)), new LongWritable(1));
062    }
063  }
064
065}