From 9f82f66f1a9ed3194889fee1b69a10287c4b03db Mon Sep 17 00:00:00 2001
From: Kai Moritz <kai@juplo.de>
Date: Sun, 17 Jul 2022 17:11:03 +0200
Subject: [PATCH] splitter: 1.0.0-spring-ingetration - using a
 `message-key-expression`

* The configuration can be simplified
* The `ChannelInterceptor` can be omitted, if a `message-key-expression`
  is specivied for the outbound channel.
---
 .../splitter/SplitterApplication.java         | 40 +++----------------
 1 file changed, 6 insertions(+), 34 deletions(-)

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 d9ba135..246fffd 100644
--- a/src/main/java/de/juplo/kafka/wordcount/splitter/SplitterApplication.java
+++ b/src/main/java/de/juplo/kafka/wordcount/splitter/SplitterApplication.java
@@ -4,23 +4,19 @@ import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
 import org.springframework.context.annotation.Bean;
+import org.springframework.expression.Expression;
+import org.springframework.expression.ExpressionParser;
 import org.springframework.expression.common.LiteralExpression;
+import org.springframework.expression.spel.standard.SpelExpressionParser;
 import org.springframework.integration.annotation.InboundChannelAdapter;
 import org.springframework.integration.annotation.ServiceActivator;
-import org.springframework.integration.channel.DirectChannel;
 import org.springframework.integration.config.EnableIntegration;
 import org.springframework.integration.kafka.inbound.KafkaMessageSource;
 import org.springframework.integration.kafka.outbound.KafkaProducerMessageHandler;
-import org.springframework.integration.support.MessageBuilder;
 import org.springframework.kafka.core.ConsumerFactory;
 import org.springframework.kafka.core.KafkaTemplate;
 import org.springframework.kafka.listener.ConsumerProperties;
-import org.springframework.kafka.support.KafkaHeaders;
-import org.springframework.messaging.Message;
-import org.springframework.messaging.MessageChannel;
 import org.springframework.messaging.MessageHandler;
-import org.springframework.messaging.MessageHeaders;
-import org.springframework.messaging.support.ChannelInterceptor;
 
 
 @SpringBootApplication
@@ -28,33 +24,6 @@ import org.springframework.messaging.support.ChannelInterceptor;
 @EnableIntegration
 public class SplitterApplication
 {
-	@Bean
-	MessageChannel words(ChannelInterceptor keyInterceptor)
-	{
-		DirectChannel words = new DirectChannel();
-		words.addInterceptor(keyInterceptor);
-		return words;
-	}
-
-	@Bean
-	ChannelInterceptor keyInterceptor ()
-	{
-		return new ChannelInterceptor()
-		{
-			@Override
-			public Message<?> preSend(Message<?> message, MessageChannel channel)
-			{
-				MessageHeaders headers = message.getHeaders();
-				Object key = headers.get(KafkaHeaders.RECEIVED_MESSAGE_KEY);
-				return
-						MessageBuilder
-								.fromMessage(message)
-								.setHeader(KafkaHeaders.MESSAGE_KEY, key)
-								.build();
-			}
-		};
-	}
-
 	@InboundChannelAdapter(channel = "recordings")
 	@Bean
 	KafkaMessageSource<String, String> source(
@@ -73,6 +42,9 @@ public class SplitterApplication
 		KafkaProducerMessageHandler<String, String> handler =
 				new KafkaProducerMessageHandler<>(kafkaTemplate);
 		handler.setTopicExpression(new LiteralExpression(properties.getOutputTopic()));
+		final ExpressionParser parser = new SpelExpressionParser();
+		Expression expression = parser.parseExpression("headers['kafka_receivedMessageKey']");
+		handler.setMessageKeyExpression(expression);
 		return handler;
 	}
 
-- 
2.20.1