content: package mrdp.ch1;
  
  import java.io.IOException;
  import java.util.StringTokenizer;
  import java.util.Map;
  
  import mrdp.utils.MRDPUtils;
  
  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.util.GenericOptionsParser;
  
  import org.apache.commons.lang.StringEscapeUtils;
  
  public class CommentWordCount {
  
  	public static class SOWordCountMapper extends
  			Mapper<Object, Text, Text, IntWritable> {
  
  		private final static IntWritable one = new IntWritable(1);
  		private Text word = new Text();
  
  		public void map(Object key, Text value, Context context)
  				throws IOException, InterruptedException {
  
  			// Parse the input string into a nice map
  			Map<String, String> parsed = MRDPUtils.transformXmlToMap(value
  					.toString());
  
  			// Grab the "Text" field, since that is what we are counting over
  			String txt = parsed.get("Text");
  
  			// .get will return null if the key is not there
  			if (txt == null) {
  				// skip this record
  				return;
  			}
  
  			// Unescape the HTML because the SO data is escaped.
  			txt = StringEscapeUtils.unescapeHtml(txt.toLowerCase());
  
  			// Remove some annoying punctuation
  			txt = txt.replaceAll("'", ""); // remove single quotes (e.g., can't)
  			txt = txt.replaceAll("[^a-zA-Z]", " "); // replace the rest with a
  													// space
  
  			// Tokenize the string, then send the tokens away
  			StringTokenizer itr = new StringTokenizer(txt);
  			while (itr.hasMoreTokens()) {
  				word.set(itr.nextToken());
  				context.write(word, one);
  			}
  		}
  	}
  
  	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();
  		String[] otherArgs = new GenericOptionsParser(conf, args)
  				.getRemainingArgs();
  		if (otherArgs.length != 2) {
  			System.err.println("Usage: CommentWordCount <in> <out>");
  			System.exit(2);
  		}
  		Job job = new Job(conf, "StackOverflow Comment Word Count");
  		job.setJarByClass(CommentWordCount.class);
  		job.setMapperClass(SOWordCountMapper.class);
  		job.setCombinerClass(IntSumReducer.class);
  		job.setReducerClass(IntSumReducer.class);
  		job.setOutputKeyClass(Text.class);
  		job.setOutputValueClass(IntWritable.class);
  		FileInputFormat.addInputPath(job, new Path(otherArgs[0]));
  		FileOutputFormat.setOutputPath(job, new Path(otherArgs[1]));
  		System.exit(job.waitForCompletion(true) ? 0 : 1);
  	}
  }
  