org.apache.hadoop.examples.Grep.java Source code

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Here is the source code for org.apache.hadoop.examples.Grep.java

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/**
 * 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.examples;

import java.util.Random;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.*;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.input.SequenceFileInputFormat;
import org.apache.hadoop.mapreduce.lib.map.InverseMapper;
import org.apache.hadoop.mapreduce.lib.map.RegexMapper;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.mapreduce.lib.output.SequenceFileOutputFormat;
import org.apache.hadoop.mapreduce.lib.reduce.LongSumReducer;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;

/* Extracts matching regexs from input files and counts them. */
public class Grep extends Configured implements Tool {
    private Grep() {
    } // singleton

    public int run(String[] args) throws Exception {
        if (args.length < 3) {
            System.out.println("Grep <inDir> <outDir> <regex> [<group>]");
            ToolRunner.printGenericCommandUsage(System.out);
            return 2;
        }

        Path tempDir = new Path("grep-temp-" + Integer.toString(new Random().nextInt(Integer.MAX_VALUE)));

        Configuration conf = getConf();
        conf.set(RegexMapper.PATTERN, args[2]);
        if (args.length == 4)
            conf.set(RegexMapper.GROUP, args[3]);

        Job grepJob = Job.getInstance(conf);

        try {

            grepJob.setJobName("grep-search");
            grepJob.setJarByClass(Grep.class);

            FileInputFormat.setInputPaths(grepJob, args[0]);

            grepJob.setMapperClass(RegexMapper.class);

            grepJob.setCombinerClass(LongSumReducer.class);
            grepJob.setReducerClass(LongSumReducer.class);

            FileOutputFormat.setOutputPath(grepJob, tempDir);
            grepJob.setOutputFormatClass(SequenceFileOutputFormat.class);
            grepJob.setOutputKeyClass(Text.class);
            grepJob.setOutputValueClass(LongWritable.class);

            grepJob.waitForCompletion(true);

            Job sortJob = Job.getInstance(conf);
            sortJob.setJobName("grep-sort");
            sortJob.setJarByClass(Grep.class);

            FileInputFormat.setInputPaths(sortJob, tempDir);
            sortJob.setInputFormatClass(SequenceFileInputFormat.class);

            sortJob.setMapperClass(InverseMapper.class);

            sortJob.setNumReduceTasks(1); // write a single file
            FileOutputFormat.setOutputPath(sortJob, new Path(args[1]));
            sortJob.setSortComparatorClass( // sort by decreasing freq
                    LongWritable.DecreasingComparator.class);

            sortJob.waitForCompletion(true);
        } finally {
            FileSystem.get(conf).delete(tempDir, true);
        }
        return 0;
    }

    public static void main(String[] args) throws Exception {
        int res = ToolRunner.run(new Configuration(), new Grep(), args);
        System.exit(res);
    }

}