juplo.de Git - demos/kafka/wordcount/blob - src/main/java/de/juplo/kafka/wordcount/counter/CounterStreamProcessor.java

   1 package de.juplo.kafka.wordcount.counter;
   2
   3 import com.fasterxml.jackson.core.JsonProcessingException;
   4 import com.fasterxml.jackson.databind.ObjectMapper;
   5 import lombok.extern.slf4j.Slf4j;
   6 import org.apache.kafka.streams.KafkaStreams;
   7 import org.apache.kafka.streams.KeyValue;
   8 import org.apache.kafka.streams.StreamsBuilder;
   9 import org.apache.kafka.streams.kstream.KStream;
  10
  11 import java.util.Properties;
  12
  13
  14 @Slf4j
  15 public class CounterStreamProcessor
  16 {
  17         public final KafkaStreams streams;
  18
  19
  20         public CounterStreamProcessor(
  21                         String inputTopic,
  22                         String outputTopic,
  23                         Properties properties,
  24                         ObjectMapper mapper)
  25         {
  26                 StreamsBuilder builder = new StreamsBuilder();
  27
  28                 KStream<String, String> source = builder.stream(inputTopic);
  29                 source
  30                                 .map((username, word) ->
  31                                 {
  32                                         try
  33                                         {
  34                                                 String key = mapper.writeValueAsString(Key.of(username, word));
  35                                                 return new KeyValue<>(key, word);
  36                                         }
  37                                         catch (JsonProcessingException e)
  38                                         {
  39                                                 throw new RuntimeException(e);
  40                                         }
  41                                 })
  42                                 .groupByKey()
  43                                 .count()
  44                                 .mapValues(value->Long.toString(value))
  45                                 .toStream()
  46                                 .to(outputTopic);
  47
  48                 streams = new KafkaStreams(builder.build(), properties);
  49         }
  50
  51         public void start()
  52         {
  53                 log.info("Starting Stream-Processor");
  54                 streams.start();
  55         }
  56
  57         public void stop()
  58         {
  59                 log.info("Stopping Stream-Processor");
  60                 streams.close();
  61         }
  62 }