WordCount.java

/**
 * Word Count Bolt counts the occurrences of each word that it receives.
 *
 *
 * @author Tarun Sharma
 * @version 1.0
 * @see <a href="http://www.dream-lab.in/">DREAM:Lab</a>
 *
 * Copyright 2014 DREAM:Lab, Indian Institute of Science, 2014
 *
 * Licensed 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 mypackage.bolts;

import java.util.HashMap;
import java.util.Map;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import backtype.storm.task.OutputCollector;
import backtype.storm.task.TopologyContext;
import backtype.storm.topology.OutputFieldsDeclarer;
import backtype.storm.topology.base.BaseRichBolt;
import backtype.storm.tuple.Fields;
import backtype.storm.tuple.Tuple;
import backtype.storm.tuple.Values;

public class WordCount extends BaseRichBolt{
	/**
	 * 
	 */
	private static final long serialVersionUID = -4782405675667761922L;
	private static Logger LOG = LoggerFactory.getLogger(WordCount.class);
	OutputCollector collector;
	Map<String, Integer> counts = new HashMap<String, Integer>();

	@Override
	public void prepare(Map stormConf, TopologyContext context,
			OutputCollector collector) {
		// TODO Auto-generated method stub
		this.collector = collector;
	}
	
    @Override
    public void execute(Tuple tuple) {
      String word = tuple.getString(0);
      Integer count = counts.get(word);
      LOG.info("Inside WordCount anchors to ids is " + tuple.getMessageId().getAnchorsToIds());
      if (count == null)
        count = 0;
      count++;
      counts.put(word, count);
      collector.emit(tuple, new Values(word, count));
      collector.ack(tuple);
    }

    @Override
    public void declareOutputFields(OutputFieldsDeclarer declarer) {
      declarer.declare(new Fields("word", "count"));
    }

}