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.Topology;
  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                         ObjectMapper mapper)
  29         {
  30                 Topology topology = CounterStreamProcessor.buildTopology(
  31                                 inputTopic,
  32                                 outputTopic,
  33                                 storeSupplier,
  34                                 mapper);
  35
  36                 streams = new KafkaStreams(topology, properties);
  37         }
  38
  39         static Topology buildTopology(
  40                         String inputTopic,
  41                         String outputTopic,
  42                         KeyValueBytesStoreSupplier storeSupplier,
  43                         ObjectMapper mapper)
  44         {
  45                 StreamsBuilder builder = new StreamsBuilder();
  46
  47                 KStream<String, String> source = builder.stream(inputTopic);
  48                 source
  49                                 .map((username, word) ->
  50                                 {
  51                                         try
  52                                         {
  53                                                 String key = mapper.writeValueAsString(Key.of(username, word));
  54                                                 return new KeyValue<>(key, word);
  55                                         }
  56                                         catch (JsonProcessingException e)
  57                                         {
  58                                                 throw new RuntimeException(e);
  59                                         }
  60                                 })
  61                                 .groupByKey()
  62                                 .count(Materialized.as(storeSupplier))
  63                                 .mapValues(value->Long.toString(value))
  64                                 .toStream()
  65                                 .to(outputTopic);
  66
  67                 return builder.build();
  68         }
  69
  70         public void start()
  71         {
  72                 log.info("Starting Stream-Processor");
  73                 streams.start();
  74         }
  75
  76         public void stop()
  77         {
  78                 log.info("Stopping Stream-Processor");
  79                 streams.close();
  80         }
  81 }