Polish Kafka transaction support property

Closes gh-11076

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

@@ -96,11 +96,12 @@ public class KafkaAutoConfiguration {
 	@Bean
 	@ConditionalOnMissingBean(ProducerFactory.class)
 	public ProducerFactory<?, ?> kafkaProducerFactory() {
-		DefaultKafkaProducerFactory<Object, Object> factory = new DefaultKafkaProducerFactory<>(
+		DefaultKafkaProducerFactory<?, ?> factory = new DefaultKafkaProducerFactory<>(
 				this.properties.buildProducerProperties());
-		KafkaProperties.Producer producer = this.properties.getProducer();
+		String transactionIdPrefix = this.properties.getProducer()
-		if (producer.getTransactionIdPrefix() != null) {
+				.getTransactionIdPrefix();
-			factory.setTransactionIdPrefix(producer.getTransactionIdPrefix());
+		if (transactionIdPrefix != null) {
+			factory.setTransactionIdPrefix(transactionIdPrefix);
 		}
 		return factory;
 	}
@@ -108,7 +109,8 @@ public class KafkaAutoConfiguration {
 	@Bean
 	@ConditionalOnProperty(name = "spring.kafka.producer.transaction-id-prefix")
 	@ConditionalOnMissingBean
-	public KafkaTransactionManager<?, ?> kafkaTransactionManager(ProducerFactory<?, ?> producerFactory) {
+	public KafkaTransactionManager<?, ?> kafkaTransactionManager(
+			ProducerFactory<?, ?> producerFactory) {
 		return new KafkaTransactionManager<>(producerFactory);
 	}
 

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

@@ -521,7 +521,7 @@ public class KafkaProperties {
 		private Integer retries;
 
 		/**
-		 * When non empty, enables transactional support for producer.
+		 * When non empty, enables transaction support for producer.
 		 */
 		private String transactionIdPrefix;
 

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

@@ -200,9 +200,8 @@ public class KafkaAutoConfigurationTests {
 					assertThat(
 							context.getBeansOfType(KafkaJaasLoginModuleInitializer.class))
 									.isEmpty();
-					assertThat(
+					assertThat(context.getBeansOfType(KafkaTransactionManager.class))
-							context.getBeansOfType(KafkaTransactionManager.class))
+							.isEmpty();
-									.isEmpty();
 					assertThat(configs.get("foo.bar.baz")).isEqualTo("qux.fiz.buz");
 					assertThat(configs.get("fiz.buz")).isEqualTo("fix.fox");
 				});
@@ -303,8 +302,7 @@ public class KafkaAutoConfigurationTests {
 					assertThat(dfa.getPropertyValue("loginModule")).isEqualTo("foo");
 					assertThat(dfa.getPropertyValue("controlFlag")).isEqualTo(
 							AppConfigurationEntry.LoginModuleControlFlag.REQUISITE);
-					assertThat(
+					assertThat(context.getBeansOfType(KafkaTransactionManager.class))
-							context.getBeansOfType(KafkaTransactionManager.class))
 							.hasSize(1);
 					assertThat(((Map<String, String>) dfa.getPropertyValue("options")))
 							.containsExactly(entry("useKeyTab", "true"));

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

@@ -998,6 +998,7 @@ content into your application; rather pick only the properties that you need.
 	spring.kafka.producer.ssl.keystore-password= # Store password for the key store file.
 	spring.kafka.producer.ssl.truststore-location= # Location of the trust store file.
 	spring.kafka.producer.ssl.truststore-password= # Store password for the trust store file.
+	spring.kafka.producer.transaction-id-prefix= # When non empty, enables transaction support for producer.
 	spring.kafka.producer.value-serializer= # Serializer class for values.
 	spring.kafka.properties.*= # Additional properties, common to producers and consumers, used to configure the client.
 	spring.kafka.ssl.key-password= # Password of the private key in the key store file.