RandomSentenceSpout.java

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package com.abinash.example;

/**
 *
 * @author Abinash
 * 
 */

import org.apache.storm.spout.SpoutOutputCollector;
import org.apache.storm.task.TopologyContext;
import org.apache.storm.topology.OutputFieldsDeclarer;
import org.apache.storm.topology.base.BaseRichSpout;
import org.apache.storm.tuple.Fields;
import org.apache.storm.tuple.Values;
import org.apache.storm.utils.Utils;

import java.util.Map;
import java.util.Random;

//This spout randomly emits sentences
public class RandomSentenceSpout extends BaseRichSpout {
    //Collector used to emit output
    SpoutOutputCollector _collector;
    //Used to generate a random number
    Random _rand;
      
    //Open is called when an instance of the class is created
    @Override
    public void open(Map conf, TopologyContext context, SpoutOutputCollector collector) {
    //Set the instance collector to the one passed in
    _collector = collector;
    //For randomness
    _rand = new Random();
    } 
    
    //Emit data to the stream
    @Override
    public void nextTuple() {
    //Sleep for a bit
    Utils.sleep(100);
    //The sentences that are randomly emitted
    String[] sentences = new String[]{"the cow jumped over the moon", "an apple a day keeps the doctor away","four score and seven years ago", "snow white and the seven dwarfs", "i am at two with nature" };
    //Randomly pick a sentence
    String sentence  = sentences[_rand.nextInt(sentences.length)];
    //Emit the sentence
    _collector.emit(new Values(sentence));
    }
    
    //Ack is not implemented since this is a basic example 
    @Override 
    public void ack(Object id) {
    }
    
    //Fail is not implemented since this is a basic example
    @Override
    public void fail(Object id) {
    }
    
    //Declare the output fields . In this case, an sentence 
    @Override 
    public void declareOutputFields(OutputFieldsDeclarer declarer) {
        declarer.declare(new Fields("sentence"));
    }
}