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}