import lombok.extern.slf4j.Slf4j;
import org.apache.kafka.streams.*;
-import org.apache.kafka.streams.kstream.KStream;
+import org.apache.kafka.streams.kstream.Consumed;
import org.apache.kafka.streams.kstream.Materialized;
+import org.apache.kafka.streams.kstream.Produced;
import org.apache.kafka.streams.state.KeyValueBytesStoreSupplier;
import org.apache.kafka.streams.state.QueryableStoreTypes;
import org.apache.kafka.streams.state.ReadOnlyKeyValueStore;
+import org.springframework.kafka.support.serializer.JsonSerde;
+import org.springframework.kafka.support.serializer.JsonSerializer;
+import java.util.Map;
import java.util.Properties;
+import java.util.stream.Collectors;
@Slf4j
{
StreamsBuilder builder = new StreamsBuilder();
- KStream<User, Word> source = builder.stream(inputTopic);
-
- source
+ builder
+ .stream(inputTopic, Consumed.with(inKeySerde(), inValueSerde()))
.map((key, word) -> new KeyValue<>(word, word))
.groupByKey()
- .count(Materialized.as(storeSupplier))
+ .count(
+ Materialized
+ .<Word, Long>as(storeSupplier)
+ .withKeySerde(new JsonSerde<>(Word.class))) // No headers are present: fixed typing is needed!
.toStream()
.map((word, counter) -> new KeyValue<>(word, WordCounter.of(word, counter)))
- .to(outputTopic);
+ .to(outputTopic, Produced.with(outKeySerde(), outValueSerde()));
Topology topology = builder.build();
log.info("\n\n{}", topology.describe());
log.info("Stopping Stream-Processor");
streams.close();
}
+
+
+
+ public static JsonSerde<User> inKeySerde()
+ {
+ return new JsonSerde<>(User.class);
+ }
+
+ public static JsonSerde<Word> inValueSerde()
+ {
+ return new JsonSerde<>(Word.class);
+ }
+
+ public static JsonSerde<Word> outKeySerde()
+ {
+ return serde(true);
+ }
+
+ public static JsonSerde<WordCounter> outValueSerde()
+ {
+ return serde(false);
+ }
+
+ public static <T> JsonSerde<T> serde(boolean isKey)
+ {
+ JsonSerde<T> serde = new JsonSerde<>();
+ serde.configure(
+ Map.of(JsonSerializer.TYPE_MAPPINGS, typeMappingsConfig()),
+ isKey);
+ return serde;
+ }
+
+ private static String typeMappingsConfig()
+ {
+ return typeMappingsConfig(Word.class, WordCounter.class);
+ }
+
+ public static String typeMappingsConfig(Class wordClass, Class wordCounterClass)
+ {
+ return Map.of(
+ "word", wordClass,
+ "counter", wordCounterClass)
+ .entrySet()
+ .stream()
+ .map(entry -> entry.getKey() + ":" + entry.getValue().getName())
+ .collect(Collectors.joining(","));
+ }
}