juplo.de Git - demos/kafka/wordcount/blob - src/main/java/de/juplo/kafka/wordcount/top10/Top10StreamProcessor.java

   1 package de.juplo.kafka.wordcount.top10;
   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
  10 import java.util.Properties;
  11
  12
  13 @Slf4j
  14 public class Top10StreamProcessor
  15 {
  16         public final KafkaStreams streams;
  17
  18
  19         public Top10StreamProcessor(
  20                         String inputTopic,
  21                         String outputTopic,
  22                         ObjectMapper mapper,
  23                         Properties props)
  24         {
  25                 StreamsBuilder builder = new StreamsBuilder();
  26
  27                 builder
  28                                 .<String, String>stream(inputTopic)
  29                                 .map((keyJson, countStr) ->
  30                                 {
  31                                         try
  32                                         {
  33                                                 Key key = mapper.readValue(keyJson, Key.class);
  34                                                 Long count = Long.parseLong(countStr);
  35                                                 Entry entry = Entry.of(key.getWord(), count);
  36                                                 String entryJson = mapper.writeValueAsString(entry);
  37                                                 return new KeyValue<>(key.getUsername(), entryJson);
  38                                         }
  39                                         catch (JsonProcessingException e)
  40                                         {
  41                                                 throw new RuntimeException(e);
  42                                         }
  43                                 })
  44                                 .groupByKey()
  45                                 .aggregate(
  46                                                 () -> "{\"entries\"     : []}",
  47                                                 (username, entryJson, rankingJson) ->
  48                                                 {
  49                                                         try
  50                                                         {
  51                                                                 Ranking ranking = mapper.readValue(rankingJson, Ranking.class);
  52                                                                 ranking.add(mapper.readValue(entryJson, Entry.class));
  53                                                                 return mapper.writeValueAsString(ranking);
  54                                                         }
  55                                                         catch (JsonProcessingException e)
  56                                                         {
  57                                                                 throw new RuntimeException(e);
  58                                                         }
  59                                                 }
  60                                 )
  61                                 .toStream()
  62                                 .to(outputTopic);
  63
  64                 streams = new KafkaStreams(builder.build(), props);
  65         }
  66
  67         public void start()
  68         {
  69                 log.info("Starting Stream-Processor");
  70                 streams.start();
  71         }
  72
  73         public void stop()
  74         {
  75                 log.info("Stopping Stream-Processor");
  76                 streams.close();
  77         }
  78 }