splitter: 1.0.0-spring-ingetration - extract the key on the inbound channel

* The key of the Kafka-Message is extracted on the inbound channel with
  a `HeaderEnricher`.
* This way, the key is propagated to dreived messages automatically.

diff --git a/src/main/java/de/juplo/kafka/wordcount/splitter/SplitterApplication.java b/src/main/java/de/juplo/kafka/wordcount/splitter/SplitterApplication.java
index 3828050..8bd928b 100644 (file)
--- a/src/main/java/de/juplo/kafka/wordcount/splitter/SplitterApplication.java
+++ b/src/main/java/de/juplo/kafka/wordcount/splitter/SplitterApplication.java
@@ -9,16 +9,23 @@ import org.springframework.expression.ExpressionParser;
 import org.springframework.expression.common.LiteralExpression;
 import org.springframework.expression.spel.standard.SpelExpressionParser;
 import org.springframework.integration.annotation.ServiceActivator;
+import org.springframework.integration.annotation.Transformer;
 import org.springframework.integration.config.EnableIntegration;
 import org.springframework.integration.core.MessageProducer;
 import org.springframework.integration.kafka.inbound.KafkaMessageDrivenChannelAdapter;
 import org.springframework.integration.kafka.outbound.KafkaProducerMessageHandler;
+import org.springframework.integration.transformer.HeaderEnricher;
+import org.springframework.integration.transformer.support.ExpressionEvaluatingHeaderValueMessageProcessor;
+import org.springframework.integration.transformer.support.HeaderValueMessageProcessor;
 import org.springframework.kafka.core.ConsumerFactory;
 import org.springframework.kafka.core.KafkaTemplate;
 import org.springframework.kafka.listener.ContainerProperties;
 import org.springframework.kafka.listener.KafkaMessageListenerContainer;
 import org.springframework.messaging.MessageHandler;
 
+import java.util.HashMap;
+import java.util.Map;
+
 
 @SpringBootApplication
 @EnableConfigurationProperties(SplitterApplicationProperties.class)
@@ -31,10 +38,24 @@ public class SplitterApplication
        {
                KafkaMessageDrivenChannelAdapter<String, String> adapter =
                                new KafkaMessageDrivenChannelAdapter(messageListenerContainer);
-               adapter.setOutputChannelName("recordings");
+               adapter.setOutputChannelName("kafka-in");
                return adapter;
        }
 
+       @Bean
+       @Transformer(inputChannel = "kafka-in", outputChannel = "recordings")
+       public HeaderEnricher kafkaInHeaderEnricher()
+       {
+               Map<String, HeaderValueMessageProcessor<?>> headersToAdd = new HashMap<>();
+               Expression expression =
+                               new SpelExpressionParser().parseExpression("headers['kafka_receivedMessageKey']");
+               headersToAdd.put(
+                               "key",
+                               new ExpressionEvaluatingHeaderValueMessageProcessor<>(expression, String.class));
+               HeaderEnricher enricher = new HeaderEnricher(headersToAdd);
+               return enricher;
+       }
+
        @Bean
        KafkaMessageListenerContainer<String, String> messageListenerContainer(
                        ConsumerFactory<String,String> consumerFactory,
@@ -56,7 +77,7 @@ public class SplitterApplication
                                new KafkaProducerMessageHandler<>(kafkaTemplate);
                handler.setTopicExpression(new LiteralExpression(properties.getOutputTopic()));
                final ExpressionParser parser = new SpelExpressionParser();
-               Expression expression = parser.parseExpression("headers['kafka_receivedMessageKey']");
+               Expression expression = parser.parseExpression("headers['key']");
                handler.setMessageKeyExpression(expression);
                return handler;
        }