Polish "Auto-configure Kafka MessageConverter"

Closes gh-10380

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/kafka/ConcurrentKafkaListenerContainerFactoryConfigurer.java

@@ -20,7 +20,7 @@ import org.springframework.boot.autoconfigure.kafka.KafkaProperties.Listener;
 import org.springframework.kafka.config.ConcurrentKafkaListenerContainerFactory;
 import org.springframework.kafka.core.ConsumerFactory;
 import org.springframework.kafka.listener.config.ContainerProperties;
-import org.springframework.kafka.support.converter.MessageConverter;
+import org.springframework.kafka.support.converter.RecordMessageConverter;
 
 /**
  * Configure {@link ConcurrentKafkaListenerContainerFactory} with sensible defaults.
@@ -33,7 +33,7 @@ public class ConcurrentKafkaListenerContainerFactoryConfigurer {
 
 	private KafkaProperties properties;
 
-	private MessageConverter messageConverter;
+	private RecordMessageConverter messageConverter;
 
 	/**
 	 * Set the {@link KafkaProperties} to use.
@@ -44,10 +44,10 @@ public class ConcurrentKafkaListenerContainerFactoryConfigurer {
 	}
 
 	/**
-	 * Set the {@link MessageConverter} to use.
+	 * Set the {@link RecordMessageConverter} to use.
 	 * @param messageConverter the message converter
 	 */
-	public void setMessageConverter(MessageConverter messageConverter) {
+	void setMessageConverter(RecordMessageConverter messageConverter) {
 		this.messageConverter = messageConverter;
 	}
 
@@ -61,10 +61,10 @@ public class ConcurrentKafkaListenerContainerFactoryConfigurer {
 	public void configure(
 			ConcurrentKafkaListenerContainerFactory<Object, Object> listenerContainerFactory,
 			ConsumerFactory<Object, Object> consumerFactory) {
+		listenerContainerFactory.setConsumerFactory(consumerFactory);
 		if (this.messageConverter != null) {
 			listenerContainerFactory.setMessageConverter(this.messageConverter);
 		}
-		listenerContainerFactory.setConsumerFactory(consumerFactory);
 		Listener container = this.properties.getListener();
 		ContainerProperties containerProperties = listenerContainerFactory
 				.getContainerProperties();

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/kafka/KafkaAnnotationDrivenConfiguration.java

@@ -25,7 +25,7 @@ import org.springframework.kafka.annotation.EnableKafka;
 import org.springframework.kafka.config.ConcurrentKafkaListenerContainerFactory;
 import org.springframework.kafka.config.KafkaListenerConfigUtils;
 import org.springframework.kafka.core.ConsumerFactory;
-import org.springframework.kafka.support.converter.MessageConverter;
+import org.springframework.kafka.support.converter.RecordMessageConverter;
 
 /**
  * Configuration for Kafka annotation-driven support.
@@ -40,12 +40,12 @@ class KafkaAnnotationDrivenConfiguration {
 
 	private final KafkaProperties properties;
 
-	private final MessageConverter messageConverter;
+	private final RecordMessageConverter messageConverter;
 
 	KafkaAnnotationDrivenConfiguration(KafkaProperties properties,
-			ObjectProvider<MessageConverter> messageConverter) {
+			ObjectProvider<RecordMessageConverter> messageConverter) {
 		this.properties = properties;
-		this.messageConverter = messageConverter.getIfAvailable();
+		this.messageConverter = messageConverter.getIfUnique();
 	}
 
 	@Bean

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/kafka/KafkaAutoConfiguration.java

@@ -60,7 +60,7 @@ public class KafkaAutoConfiguration {
 	public KafkaAutoConfiguration(KafkaProperties properties,
 			ObjectProvider<RecordMessageConverter> messageConverter) {
 		this.properties = properties;
-		this.messageConverter = messageConverter.getIfAvailable();
+		this.messageConverter = messageConverter.getIfUnique();
 	}
 
 	@Bean

spring-boot-docs/src/main/asciidoc/spring-boot-features.adoc

@@ -4846,6 +4846,8 @@ public class MyBean {
 }
 ----
 
+NOTE: If a `RecordMessageConverter` bean is defined, it is associated automatically to the
+auto-configured `KafkaTemplate`.
 
 
 [[boot-features-kafka-receiving-a-message]]
@@ -4853,7 +4855,8 @@ public class MyBean {
 When the Apache Kafka infrastructure is present, any bean can be annotated with
 `@KafkaListener` to create a listener endpoint. If no `KafkaListenerContainerFactory`
 has been defined, a default one is configured automatically with keys defined in
-`spring.kafka.listener.*`.
+`spring.kafka.listener.*`. Also, if a `RecordMessageConverter` bean is defined, it is
+associated automatically to the default factory.
 
 The following component creates a listener endpoint on the `someTopic` topic: