新版API多檔案輸入

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 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
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 * 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
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 * See the License for the specific language governing permissions and
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package org.apache.hadoop.examples;

import java.io.IOException;
import java.util.StringTokenizer;

import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.lib.input.MultipleInputs;
import org.apache.hadoop.mapreduce.lib.input.TextInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;

/**
 * NewMultiFileWordCount is an example to demonstrate the usage of
 * MultipleInputs. This examples counts the occurrences of words in the
 * text files under the given input directory.
 */
public class NewMultiFileWordCount extends Configured implements Tool {
/**
* This Mapper is similar to the one in {@link HadoopTest.MapClass}.
*/
public static class MapClass extends Mapper<LongWritable, Text, Text, LongWritable> {

private final static LongWritable one = new LongWritable(1);
private Text word = new Text();

public void map(LongWritable key, Text value, Context context)  throws IOException, InterruptedException {
String line = value.toString();
StringTokenizer itr = new StringTokenizer(line);
while (itr.hasMoreTokens()) {
word.set(itr.nextToken());
context.write(word, one);
}
}
}

private void printUsage() {
System.out.println("Usage : multifilewc <input_dir> <output>");
}

public int run(String[] args) throws Exception {

if (args.length < 2) {
printUsage();
return 1;
}

Job job = new Job(getConf());
job.setJobName("MultiFileWordCount");
job.setJarByClass(NewMultiFileWordCount.class);
// the keys are words (strings)
job.setOutputKeyClass(Text.class);
// the values are counts (ints)
job.setOutputValueClass(LongWritable.class);

// use the WordCount Reducer
job.setCombinerClass(LongSumReducer.class);
job.setReducerClass(LongSumReducer.class);

MultipleInputs.addInputPath(job, new Path(args[0]), TextInputFormat.class, MapClass.class);

MultipleInputs.addInputPath(job, new Path(args[0]), TextInputFormat.class, MapClass.class);
FileOutputFormat.setOutputPath(job, new Path(args[1]));

System.exit(job.waitForCompletion(true) ? 0 : 1);

return 0;
}

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

}

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