/** * Copyright 2005 The Apache Software Foundation * * Licensed 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.examples;import org.apache.hadoop.mapred.JobConf;import org.apache.hadoop.mapred.JobClient;import org.apache.hadoop.mapred.SequenceFileOutputFormat;import org.apache.hadoop.mapred.SequenceFileInputFormat;import org.apache.hadoop.mapred.lib.RegexMapper;import org.apache.hadoop.mapred.lib.InverseMapper;import org.apache.hadoop.mapred.lib.LongSumReducer;import org.apache.hadoop.io.UTF8;import org.apache.hadoop.io.LongWritable;import org.apache.hadoop.conf.Configuration;import java.io.File;import java.util.Random;/* Extracts matching regexs from input files and counts them. */public class Grep {  private Grep() {}                               // singleton  public static void main(String[] args) throws Exception {    if (args.length < 3) {      System.out.println("Grep <inDir> <outDir> <regex> [<group>]");      System.exit(-1);    }    Configuration defaults = new Configuration();    File tempDir =      new File("grep-temp-"+               Integer.toString(new Random().nextInt(Integer.MAX_VALUE)));    JobConf grepJob = new JobConf(defaults, Grep.class);    grepJob.setJobName("grep-search");    grepJob.setInputDir(new File(args[0]));    grepJob.setMapperClass(RegexMapper.class);    grepJob.set("mapred.mapper.regex", args[2]);    if (args.length == 4)      grepJob.set("mapred.mapper.regex.group", args[3]);        grepJob.setCombinerClass(LongSumReducer.class);    grepJob.setReducerClass(LongSumReducer.class);    grepJob.setOutputDir(tempDir);    grepJob.setOutputFormat(SequenceFileOutputFormat.class);    grepJob.setOutputKeyClass(UTF8.class);    grepJob.setOutputValueClass(LongWritable.class);    JobClient.runJob(grepJob);    JobConf sortJob = new JobConf(defaults, Grep.class);    sortJob.setJobName("grep-sort");    sortJob.setInputDir(tempDir);    sortJob.setInputFormat(SequenceFileInputFormat.class);    sortJob.setInputKeyClass(UTF8.class);    sortJob.setInputValueClass(LongWritable.class);    sortJob.setMapperClass(InverseMapper.class);    sortJob.setNumReduceTasks(1);                 // write a single file    sortJob.setOutputDir(new File(args[1]));    sortJob.setOutputKeyComparatorClass           // sort by decreasing freq      (LongWritable.DecreasingComparator.class);    JobClient.runJob(sortJob);    new JobClient(defaults).getFs().delete(tempDir);  }}