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 import org.apache.kafka.streams.kstream.Materialized;
  11 import org.apache.kafka.streams.state.KeyValueBytesStoreSupplier;
  12
  13 import java.util.Properties;
  14
  15
  16 @Slf4j
  17 public class CounterStreamProcessor
  18 {
  19         public final KafkaStreams streams;
  20
  21
  22         public CounterStreamProcessor(
  23                         String inputTopic,
  24                         String outputTopic,
  25                         Properties properties,
  26                         KeyValueBytesStoreSupplier storeSupplier,
  27                         ObjectMapper mapper)
  28         {
  29                 StreamsBuilder builder = new StreamsBuilder();
  30
  31                 KStream<String, String> source = builder.stream(inputTopic);
  32                 source
  33                                 .map((username, word) ->
  34                                 {
  35                                         try
  36                                         {
  37                                                 String key = mapper.writeValueAsString(Key.of(username, word));
  38                                                 return new KeyValue<>(key, word);
  39                                         }
  40                                         catch (JsonProcessingException e)
  41                                         {
  42                                                 throw new RuntimeException(e);
  43                                         }
  44                                 })
  45                                 .groupByKey()
  46                                 .count(Materialized.as(storeSupplier))
  47                                 .mapValues(value->Long.toString(value))
  48                                 .toStream()
  49                                 .to(outputTopic);
  50
  51                 streams = new KafkaStreams(builder.build(), properties);
  52         }
  53
  54         public void start()
  55         {
  56                 log.info("Starting Stream-Processor");
  57                 streams.start();
  58         }
  59
  60         public void stop()
  61         {
  62                 log.info("Stopping Stream-Processor");
  63                 streams.close();
  64         }
  65 }