Building Data Streaming Applications with Apache Kafka by Manish Kumar & Chanchal Singh

Author:Manish Kumar & Chanchal Singh [Kumar, Manish]
Language: eng
Format: azw3
Tags: COM062000 - COMPUTERS / Data Modeling and Design, COM018000 - COMPUTERS / Data Processing, COM051280 - COMPUTERS / Programming Languages / Java
Publisher: Packt Publishing
Published: 2017-08-18T04:00:00+00:00

Wordcount Bolt: Example of Wordcount Bolt is given next:

import org.apache.Storm.task.OutputCollector import org.apache.Storm.task.TopologyContext import org.apache.Storm.topology.IRichBolt import org.apache.Storm.topology.OutputFieldsDeclarer import org.apache.Storm.tuple.Tuple import java.util.HashMap import java.util.Map class WordCountCalculatorBolt extends IRichBolt { var wordCountMap: Map[String, Integer] = _ private var collector: OutputCollector = _ def prepare(StormConf: Map[_, _], context: TopologyContext, collector: OutputCollector): Unit = { this.wordCountMap = new HashMap[String, Integer]() this.collector = collector } def execute(input: Tuple): Unit = { var str: String = input.getString(0) str = str.toLowerCase().trim() if (!wordCountMap.containsKey(str)) { wordCountMap.put(str, 1) } else { val c: java.lang.Integer = wordCountMap.get(str) + 1 wordCountMap.put(str, c) } collector.ack(input) } def cleanup(): Unit = { for ((key, value) <- wordCountMap) { println(key + " : " + value) } } override def declareOutputFields(declarer: OutputFieldsDeclarer): Unit = {} override def getComponentConfiguration(): Map[String, Any] = null }

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