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 lombok.extern.slf4j.Slf4j;
   4 import org.apache.kafka.common.serialization.Serdes;
   5 import org.apache.kafka.streams.KafkaStreams;
   6 import org.apache.kafka.streams.KeyValue;
   7 import org.apache.kafka.streams.StreamsBuilder;
   8 import org.apache.kafka.streams.Topology;
   9 import org.apache.kafka.streams.kstream.Consumed;
  10 import org.apache.kafka.streams.kstream.KStream;
  11 import org.apache.kafka.streams.kstream.Materialized;
  12 import org.apache.kafka.streams.state.KeyValueBytesStoreSupplier;
  13
  14 import java.util.Properties;
  15
  16
  17 @Slf4j
  18 public class CounterStreamProcessor
  19 {
  20         public final KafkaStreams streams;
  21
  22
  23         public CounterStreamProcessor(
  24                         String inputTopic,
  25                         String outputTopic,
  26                         Properties properties,
  27                         KeyValueBytesStoreSupplier storeSupplier)
  28         {
  29                 Topology topology = CounterStreamProcessor.buildTopology(
  30                                 inputTopic,
  31                                 outputTopic,
  32                                 storeSupplier);
  33
  34                 streams = new KafkaStreams(topology, properties);
  35         }
  36
  37         static Topology buildTopology(
  38                         String inputTopic,
  39                         String outputTopic,
  40                         KeyValueBytesStoreSupplier storeSupplier)
  41         {
  42                 StreamsBuilder builder = new StreamsBuilder();
  43
  44                 KStream<String, Word> source = builder.stream(
  45                                 inputTopic,
  46                                 Consumed.with(Serdes.String(), null));
  47
  48                 source
  49                                 .map((key, word) -> new KeyValue<>(word, word))
  50                                 .groupByKey()
  51                                 .count(Materialized.as(storeSupplier))
  52                                 .toStream()
  53                                 .map((word, counter) -> new KeyValue<>(word, WordCounter.of(word, counter)))
  54                                 .to(outputTopic);
  55
  56                 Topology topology = builder.build();
  57                 log.info("\n\n{}", topology.describe());
  58
  59                 return topology;
  60         }
  61
  62         public void start()
  63         {
  64                 log.info("Starting Stream-Processor");
  65                 streams.start();
  66         }
  67
  68         public void stop()
  69         {
  70                 log.info("Stopping Stream-Processor");
  71                 streams.close();
  72         }
  73 }