Persistor.java

package stormapplied.heatmap.topology;

import backtype.storm.task.TopologyContext;
import backtype.storm.topology.BasicOutputCollector;
import backtype.storm.topology.OutputFieldsDeclarer;
import backtype.storm.topology.base.BaseBasicBolt;
import backtype.storm.tuple.Tuple;
import com.google.code.geocoder.model.LatLng;
import org.codehaus.jackson.map.ObjectMapper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import redis.clients.jedis.Jedis;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;

public class Persistor extends BaseBasicBolt {
  private final Logger logger = LoggerFactory.getLogger(Persistor.class);

  private Jedis jedis;
  private ObjectMapper objectMapper;

  @Override
  public void prepare(Map stormConf,
                      TopologyContext context) {
    jedis = new Jedis("localhost");
    objectMapper = new ObjectMapper();
  }

  @Override
  public void execute(Tuple tuple,
                      BasicOutputCollector outputCollector) {
    Long timeInterval = tuple.getLongByField("time-interval");
    List<LatLng> hz = (List<LatLng>) tuple.getValueByField("hotzones");
    List<String> hotzones = asListOfStrings(hz);

    try {
      String key = "checkins-" + timeInterval;
      String value = objectMapper.writeValueAsString(hotzones);
      jedis.set(key, value);
    } catch (Exception e) {
      logger.error("Error persisting for time: " + timeInterval, e);
    }
  }

  private List<String> asListOfStrings(List<LatLng> hotzones) {
    List<String> hotzonesStandard = new ArrayList<String>(hotzones.size());
    for (LatLng geoCoordinate : hotzones) {
      hotzonesStandard.add(geoCoordinate.toUrlValue());
    }
    return hotzonesStandard;
  }

  @Override
  public void cleanup() {
    if (jedis.isConnected()) {
      jedis.quit();
    }
  }

  @Override
  public void declareOutputFields(OutputFieldsDeclarer declarer) {
    // No output fields to be declared
  }
}