Add support for Kafka batch listener

This commit adds a `spring.kafka.listener.batch-listener` property so
that a batch listener is created automatically.

See gh-9448

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

@@ -68,6 +68,7 @@ public class ConcurrentKafkaListenerContainerFactoryConfigurer {
 		if (container.getConcurrency() != null) {
 			listenerContainerFactory.setConcurrency(container.getConcurrency());
 		}
+		listenerContainerFactory.setBatchListener(container.getBatchListener());
 	}
 
 }

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

@@ -672,6 +672,11 @@ public class KafkaProperties {
 		 */
 		private Long ackTime;
 
+		/**
+		 * If true listener container factory will be configured to create batch listener.
+		 */
+		private boolean batchListener;
+
 		public AckMode getAckMode() {
 			return this.ackMode;
 		}
@@ -712,6 +717,13 @@ public class KafkaProperties {
 			this.ackTime = ackTime;
 		}
 
+		public boolean getBatchListener() {
+			return this.batchListener;
+		}
+
+		public void setBatchListener(boolean batchListener) {
+			this.batchListener = batchListener;
+		}
 	}
 
 	public static class Ssl {

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/kafka/KafkaAutoConfigurationTests.java

@@ -176,6 +176,7 @@ public class KafkaAutoConfigurationTests {
 				"spring.kafka.listener.ack-time=456",
 				"spring.kafka.listener.concurrency=3",
 				"spring.kafka.listener.poll-timeout=2000",
+				"spring.kafka.listener.batch-listener=true",
 				"spring.kafka.jaas.enabled=true", "spring.kafka.jaas.login-module=foo",
 				"spring.kafka.jaas.control-flag=REQUISITE",
 				"spring.kafka.jaas.options.useKeyTab=true");
@@ -198,6 +199,8 @@ public class KafkaAutoConfigurationTests {
 		assertThat(dfa.getPropertyValue("concurrency")).isEqualTo(3);
 		assertThat(dfa.getPropertyValue("containerProperties.pollTimeout"))
 				.isEqualTo(2000L);
+		assertThat(dfa.getPropertyValue("batchListener"))
+				.isEqualTo(true);
 		assertThat(this.context.getBeansOfType(KafkaJaasLoginModuleInitializer.class))
 				.hasSize(1);
 		KafkaJaasLoginModuleInitializer jaas = this.context

spring-boot-docs/src/main/asciidoc/appendix-application-properties.adoc

@@ -986,6 +986,7 @@ content into your application; rather pick only the properties that you need.
 	spring.kafka.listener.ack-time= # Time in milliseconds between offset commits when ackMode is "TIME" or "COUNT_TIME".
 	spring.kafka.listener.concurrency= # Number of threads to run in the listener containers.
 	spring.kafka.listener.poll-timeout= # Timeout in milliseconds to use when polling the consumer.
+	spring.kafka.listener.batch-listener= # If true listener container factory will be configured to create batch listener.
 	spring.kafka.producer.acks= # Number of acknowledgments the producer requires the leader to have received before considering a request complete.
 	spring.kafka.producer.batch-size= # Number of records to batch before sending.
 	spring.kafka.producer.bootstrap-servers= # Comma-delimited list of host:port pairs to use for establishing the initial connection to the Kafka cluster.