Created
October 26, 2013 00:49
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WordCount v2.0 for MapReduce Tutorial
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import java.io.BufferedReader; | |
import java.io.FileReader; | |
import java.io.IOException; | |
import java.net.URI; | |
import java.util.ArrayList; | |
import java.util.HashSet; | |
import java.util.List; | |
import java.util.Set; | |
import java.util.StringTokenizer; | |
import org.apache.hadoop.conf.Configuration; | |
import org.apache.hadoop.fs.Path; | |
import org.apache.hadoop.io.IntWritable; | |
import org.apache.hadoop.io.Text; | |
import org.apache.hadoop.mapreduce.Job; | |
import org.apache.hadoop.mapreduce.Mapper; | |
import org.apache.hadoop.mapreduce.Reducer; | |
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat; | |
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat; | |
import org.apache.hadoop.mapreduce.Counter; | |
import org.apache.hadoop.util.GenericOptionsParser; | |
import org.apache.hadoop.util.StringUtils; | |
public class WordCount2 { | |
public static class TokenizerMapper | |
extends Mapper<Object, Text, Text, IntWritable>{ | |
static enum CountersEnum { INPUT_WORDS } | |
private final static IntWritable one = new IntWritable(1); | |
private Text word = new Text(); | |
private boolean caseSensitive; | |
private Set<String> patternsToSkip = new HashSet<String>(); | |
private Configuration conf; | |
private BufferedReader fis; | |
@Override | |
public void setup(Context context) throws IOException, InterruptedException { | |
conf = context.getConfiguration(); | |
caseSensitive = conf.getBoolean("wordcount.case.sensitive", true); | |
if (conf.getBoolean("wordcount.skip.patterns", true)) { | |
URI[] patternsURIs = Job.getInstance(conf).getCacheFiles(); | |
for (URI patternsURI : patternsURIs) { | |
Path patternsPath = new Path(patternsURI.getPath()); | |
String patternsFileName = patternsPath.getName().toString(); | |
parseSkipFile(patternsFileName); | |
} | |
} | |
} | |
private void parseSkipFile(String fileName) { | |
try { | |
fis = new BufferedReader(new FileReader(fileName)); | |
String pattern = null; | |
while ((pattern = fis.readLine()) != null) { | |
patternsToSkip.add(pattern); | |
} | |
} catch (IOException ioe) { | |
System.err.println("Caught exception while parsing the cached file '" | |
+ StringUtils.stringifyException(ioe)); | |
} | |
} | |
@Override | |
public void map(Object key, Text value, Context context | |
) throws IOException, InterruptedException { | |
String line = (caseSensitive) ? | |
value.toString() : value.toString().toLowerCase(); | |
for (String pattern : patternsToSkip) { | |
line = line.replaceAll(pattern, ""); | |
} | |
StringTokenizer itr = new StringTokenizer(line); | |
while (itr.hasMoreTokens()) { | |
word.set(itr.nextToken()); | |
context.write(word, one); | |
Counter counter = context.getCounter(CountersEnum.class.getName(), | |
CountersEnum.INPUT_WORDS.toString()); | |
counter.increment(1); | |
} | |
} | |
} | |
public static class IntSumReducer | |
extends Reducer<Text,IntWritable,Text,IntWritable> { | |
private IntWritable result = new IntWritable(); | |
public void reduce(Text key, Iterable<IntWritable> values, | |
Context context | |
) throws IOException, InterruptedException { | |
int sum = 0; | |
for (IntWritable val : values) { | |
sum += val.get(); | |
} | |
result.set(sum); | |
context.write(key, result); | |
} | |
} | |
public static void main(String[] args) throws Exception { | |
Configuration conf = new Configuration(); | |
GenericOptionsParser optionParser = new GenericOptionsParser(conf, args); | |
String[] remainingArgs = optionParser.getRemainingArgs(); | |
if (!(remainingArgs.length != 2 || remainingArgs.length != 4)) { | |
System.err.println("Usage: wordcount <in> <out> [-skip skipPatternFile]"); | |
System.exit(2); | |
} | |
Job job = Job.getInstance(conf, "word count"); | |
job.setJarByClass(WordCount2.class); | |
job.setMapperClass(TokenizerMapper.class); | |
job.setCombinerClass(IntSumReducer.class); | |
job.setReducerClass(IntSumReducer.class); | |
job.setOutputKeyClass(Text.class); | |
job.setOutputValueClass(IntWritable.class); | |
List<String> otherArgs = new ArrayList<String>(); | |
for (int i=0; i < remainingArgs.length; ++i) { | |
if ("-skip".equals(remainingArgs[i])) { | |
job.addCacheFile(new Path(remainingArgs[++i]).toUri()); | |
job.getConfiguration().setBoolean("wordcount.skip.patterns", true); | |
} else { | |
otherArgs.add(remainingArgs[i]); | |
} | |
} | |
FileInputFormat.addInputPath(job, new Path(otherArgs.get(0))); | |
FileOutputFormat.setOutputPath(job, new Path(otherArgs.get(1))); | |
System.exit(job.waitForCompletion(true) ? 0 : 1); | |
} | |
} |
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