KeyedSummingBatchBolt.java

package backtype.storm.testing;

import backtype.storm.coordination.BatchOutputCollector;
import backtype.storm.task.TopologyContext;
import backtype.storm.topology.OutputFieldsDeclarer;
import backtype.storm.topology.base.BaseBatchBolt;
import backtype.storm.tuple.Fields;
import backtype.storm.tuple.Tuple;
import backtype.storm.tuple.Values;
import backtype.storm.utils.Utils;
import clojure.lang.Numbers;
import java.util.HashMap;
import java.util.Map;

public class KeyedSummingBatchBolt extends BaseBatchBolt {
	BatchOutputCollector _collector;
	Object _id;
	Map<Object, Number> _sums = new HashMap<Object, Number>();

	@Override
	public void prepare(Map conf, TopologyContext context,
			BatchOutputCollector collector, Object id) {
		_collector = collector;
		_id = id;
	}

	@Override
	public void execute(Tuple tuple) {
		Object key = tuple.getValue(1);
		Number curr = Utils.get(_sums, key, 0);
		_sums.put(key, Numbers.add(curr, tuple.getValue(2)));
	}

	@Override
	public void finishBatch() {
		for (Object key : _sums.keySet()) {
			_collector.emit(new Values(_id, key, _sums.get(key)));
		}
	}

	@Override
	public void declareOutputFields(OutputFieldsDeclarer declarer) {
		declarer.declare(new Fields("tx", "key", "sum"));
	}
}