OurSimpleTopology.java

package packagename

// …
  
public class OurSimpleTopology { 
 
  public static void main(String[] args) throws Exception
  {
    // Create the topology
    TopologyBuilder builder = new TopologyBuilder();
    
    // Attach the random digit spout to the topology.
    // Use just 1 thread for the spout.
    builder.setSpout("random-digit-spout", new RandomDigitSpout());
    
    // Connect the even digit bolt to our spout. 
    // The bolt will use 2 threads and the digits will be randomly
    // shuffled/distributed among the 2 threads.
    // The third parameter is formally called the parallelism hint.
    builder.setBolt("even-digit-bolt", new EvenDigitBolt(), 2)
           .shuffleGrouping("random-digit-spout");
 
    // Connect the multiply-by-10 bolt to our even digit bolt.
    // This bolt will use 4 threads, among which data from the
    // even digit bolt will be shuffled/distributed randomly.
    builder.setBolt("multiplied-by-ten-bolt", new MultiplyByTenBolt(), 4)
           .shuffleGrouping("even-digit-bolt");
    
    // Create a configuration object.
    Config conf = new Config();
    
    // The number of independent JVM processes this topology will use.
    conf.setNumWorkers(2);
    
    // Submit our topology with the configuration.
    StormSubmitter.submitTopology("our-simple-topology", conf, builder.createTopology());
  }
}