content: 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 java.util.HashMap;
  import java.util.Map;
  
  public class KeyedSummingBatchBolt extends BaseBatchBolt {
      BatchOutputCollector _collector;
      Object _id;
      Map<Object, Integer> _sums = new HashMap<Object, Integer>();
      
      @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);
          int curr = Utils.get(_sums, key, 0);
          _sums.put(key, curr + tuple.getInteger(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"));
      }    
  }
  