Counting Hashtags with Hadoop

hadoop-count-hashtags

package org.springframework.xd.examples.hadoop;

import java.io.IOException;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.apache.commons.lang.StringEscapeUtils;
import org.apache.hadoop.conf.Configuration;
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.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.util.GenericOptionsParser;

public class HashtagCount {

  public static class TokenizerMapper extends
			Mapper<Object, Text, Text, LongWritable> {

		final static Pattern TAG_PATTERN = Pattern.compile("\"hashtags\":\\[([^\\]]*)");
		private final static LongWritable ONE = new LongWritable(1L);
		private Text word = new Text();

		public void map(Object key, Text value, Context context)
                throws IOException, InterruptedException {
            Matcher matcher = TAG_PATTERN.matcher(value.toString());
            while (matcher.find()) {
            	String found = matcher.group();
            	String cleanedString = found.replaceFirst("\"hashtags\":\\[\\{\"text\":\"", "");
            	String superPolished = cleanedString.split("\",\"")[0];

            	String useMe = superPolished;
            	if (superPolished.startsWith("\\u")) {
            		useMe = StringEscapeUtils.unescapeJava(superPolished);
            	}

                word.set(useMe.toLowerCase());
                context.write(word, ONE);
            }
		}

	}

	public static class LongSumReducer extends
			Reducer<Text, LongWritable, Text, LongWritable> {
		private LongWritable result = new LongWritable();

		public void reduce(Text key, Iterable<LongWritable> values,
				Context context) throws IOException, InterruptedException {
			int sum = 0;
			for (LongWritable val : values) {
				sum += val.get();
			}
			result.set(sum);
			context.write(key, result);
		}
	}

	public static void main(String[] args) throws Exception {
		Configuration conf = new Configuration();
		String[] otherArgs = new GenericOptionsParser(conf, args)
				.getRemainingArgs();
		if (otherArgs.length != 2) {
			System.err.println("Usage: wordcount <in> <out>");
			System.exit(2);
		}
		Job job = new Job(conf, "hashtag count");
		job.setJarByClass(HashtagCount.class);
		job.setMapperClass(TokenizerMapper.class);
		job.setCombinerClass(LongSumReducer.class);
		job.setReducerClass(LongSumReducer.class);
		job.setOutputKeyClass(Text.class);
		job.setOutputValueClass(LongWritable.class);
		FileInputFormat.addInputPath(job, new Path(otherArgs[0]));
		FileOutputFormat.setOutputPath(job, new Path(otherArgs[1]));
		System.exit(job.waitForCompletion(true) ? 0 : 1);
	}
}