package de.juplo.kafka.wordcount.top10;
-import com.fasterxml.jackson.core.JsonProcessingException;
-import com.fasterxml.jackson.databind.ObjectMapper;
import lombok.extern.slf4j.Slf4j;
import org.apache.kafka.streams.KafkaStreams;
import org.apache.kafka.streams.KeyValue;
import org.apache.kafka.streams.StreamsBuilder;
+import org.apache.kafka.streams.Topology;
import java.util.Properties;
public Top10StreamProcessor(
String inputTopic,
String outputTopic,
- ObjectMapper mapper,
Properties props)
+ {
+ Topology topology = Top10StreamProcessor.buildTopology(
+ inputTopic,
+ outputTopic);
+
+ streams = new KafkaStreams(topology, props);
+ }
+
+ static Topology buildTopology(
+ String inputTopic,
+ String outputTopic)
{
StreamsBuilder builder = new StreamsBuilder();
builder
- .<String, String>stream(inputTopic)
- .map((keyJson, countStr) ->
- {
- try
- {
- Key key = mapper.readValue(keyJson, Key.class);
- Long count = Long.parseLong(countStr);
- Entry entry = Entry.of(key.getWord(), count);
- String entryJson = mapper.writeValueAsString(entry);
- return new KeyValue<>(key.getUsername(), entryJson);
- }
- catch (JsonProcessingException e)
- {
- throw new RuntimeException(e);
- }
- })
+ .<Key, Entry>stream(inputTopic)
+ .map((key, entry) -> new KeyValue<>(key.getUser(), entry))
.groupByKey()
.aggregate(
- () -> "{\"entries\" : []}",
- (username, entryJson, rankingJson) ->
- {
- try
- {
- Ranking ranking = mapper.readValue(rankingJson, Ranking.class);
- ranking.add(mapper.readValue(entryJson, Entry.class));
- return mapper.writeValueAsString(ranking);
- }
- catch (JsonProcessingException e)
- {
- throw new RuntimeException(e);
- }
- }
- )
+ () -> new Ranking(),
+ (user, entry, ranking) -> ranking.add(entry))
.toStream()
.to(outputTopic);
- streams = new KafkaStreams(builder.build(), props);
+ Topology topology = builder.build();
+ log.info("\n\n{}", topology.describe());
+
+ return topology;
}
public void start()