Add support for arbitrary producer/consumer Kafka properties

PR #7672 Added support for arbitrary common properties.

However, Kafka emits a warning if a producer configuration contains
properties intended only for consumers, and vice versa.

The documentation showed a sample of how to write code to configure
arbitrary properties but this is inconvenient.

Add arbitrary properties to the consumer and procucer configs.

See gh-9775

Author: garyrussell

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

@@ -63,7 +63,8 @@ public class KafkaProperties {
 	private String clientId;
 
 	/**
-	 * Additional properties used to configure the client.
+	 * Additional properties, common to producers and consumers, used to configure the
+	 * client.
 	 */
 	private Map<String, String> properties = new HashMap<>();
 
@@ -268,6 +269,11 @@ public static class Consumer {
 		 */
 		private Integer maxPollRecords;
 
+		/**
+		 * Additional properties used to configure the client.
+		 */
+		private Map<String, String> properties = new HashMap<>();
+
 		public Ssl getSsl() {
 			return this.ssl;
 		}
@@ -368,6 +374,14 @@ public void setMaxPollRecords(Integer maxPollRecords) {
 			this.maxPollRecords = maxPollRecords;
 		}
 
+		public Map<String, String> getProperties() {
+			return this.properties;
+		}
+
+		public void setProperties(Map<String, String> properties) {
+			this.properties = properties;
+		}
+
 		public Map<String, Object> buildProperties() {
 			Map<String, Object> properties = new HashMap<>();
 			if (this.autoCommitInterval != null) {
@@ -435,6 +449,7 @@ public Map<String, Object> buildProperties() {
 				properties.put(ConsumerConfig.MAX_POLL_RECORDS_CONFIG,
 						this.maxPollRecords);
 			}
+			properties.putAll(this.properties);
 			return properties;
 		}
 
@@ -492,6 +507,11 @@ public static class Producer {
 		 */
 		private Integer retries;
 
+		/**
+		 * Additional properties used to configure the client.
+		 */
+		private Map<String, String> properties = new HashMap<>();
+
 		public Ssl getSsl() {
 			return this.ssl;
 		}
@@ -568,6 +588,14 @@ public void setRetries(Integer retries) {
 			this.retries = retries;
 		}
 
+		public Map<String, String> getProperties() {
+			return this.properties;
+		}
+
+		public void setProperties(Map<String, String> properties) {
+			this.properties = properties;
+		}
+
 		public Map<String, Object> buildProperties() {
 			Map<String, Object> properties = new HashMap<>();
 			if (this.acks != null) {
@@ -621,6 +649,7 @@ public Map<String, Object> buildProperties() {
 				properties.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG,
 						this.valueSerializer);
 			}
+			properties.putAll(this.properties);
 			return properties;
 		}
 

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

@@ -78,16 +78,15 @@ public void consumerProperties() {
 				"spring.kafka.consumer.client-id=ccid", // test override common
 				"spring.kafka.consumer.enable-auto-commit=false",
 				"spring.kafka.consumer.fetch-max-wait=456",
+				"spring.kafka.consumer.properties.fiz.buz=fix.fox",
 				"spring.kafka.consumer.fetch-min-size=789",
 				"spring.kafka.consumer.group-id=bar",
 				"spring.kafka.consumer.heartbeat-interval=234",
 				"spring.kafka.consumer.key-deserializer = org.apache.kafka.common.serialization.LongDeserializer",
 				"spring.kafka.consumer.value-deserializer = org.apache.kafka.common.serialization.IntegerDeserializer");
 		DefaultKafkaConsumerFactory<?, ?> consumerFactory = this.context
 				.getBean(DefaultKafkaConsumerFactory.class);
-		@SuppressWarnings("unchecked")
-		Map<String, Object> configs = (Map<String, Object>) new DirectFieldAccessor(
-				consumerFactory).getPropertyValue("configs");
+		Map<String, Object> configs = consumerFactory.getConfigurationProperties();
 		// common
 		assertThat(configs.get(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG))
 				.isEqualTo(Collections.singletonList("foo:1234"));
@@ -120,17 +119,21 @@ public void consumerProperties() {
 		assertThat(configs.get("foo")).isEqualTo("bar");
 		assertThat(configs.get("baz")).isEqualTo("qux");
 		assertThat(configs.get("foo.bar.baz")).isEqualTo("qux.fiz.buz");
+		assertThat(configs.get("fiz.buz")).isEqualTo("fix.fox");
 	}
 
 	@Test
 	public void producerProperties() {
-		load("spring.kafka.clientId=cid", "spring.kafka.producer.acks=all",
+		load("spring.kafka.clientId=cid",
+				"spring.kafka.properties.foo.bar.baz=qux.fiz.buz",
+				"spring.kafka.producer.acks=all",
 				"spring.kafka.producer.batch-size=20",
 				"spring.kafka.producer.bootstrap-servers=bar:1234", // test override
 				"spring.kafka.producer.buffer-memory=12345",
 				"spring.kafka.producer.compression-type=gzip",
 				"spring.kafka.producer.key-serializer=org.apache.kafka.common.serialization.LongSerializer",
 				"spring.kafka.producer.retries=2",
+				"spring.kafka.producer.properties.fiz.buz=fix.fox",
 				"spring.kafka.producer.ssl.key-password=p4",
 				"spring.kafka.producer.ssl.keystore-location=classpath:ksLocP",
 				"spring.kafka.producer.ssl.keystore-password=p5",
@@ -139,9 +142,7 @@ public void producerProperties() {
 				"spring.kafka.producer.value-serializer=org.apache.kafka.common.serialization.IntegerSerializer");
 		DefaultKafkaProducerFactory<?, ?> producerFactory = this.context
 				.getBean(DefaultKafkaProducerFactory.class);
-		@SuppressWarnings("unchecked")
-		Map<String, Object> configs = (Map<String, Object>) new DirectFieldAccessor(
-				producerFactory).getPropertyValue("configs");
+		Map<String, Object> configs = producerFactory.getConfigurationProperties();
 		// common
 		assertThat(configs.get(ProducerConfig.CLIENT_ID_CONFIG)).isEqualTo("cid");
 		// producer
@@ -166,6 +167,8 @@ public void producerProperties() {
 				.isEqualTo(IntegerSerializer.class);
 		assertThat(this.context.getBeansOfType(KafkaJaasLoginModuleInitializer.class))
 				.isEmpty();
+		assertThat(configs.get("foo.bar.baz")).isEqualTo("qux.fiz.buz");
+		assertThat(configs.get("fiz.buz")).isEqualTo("fix.fox");
 	}
 
 	@SuppressWarnings("unchecked")

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

@@ -968,6 +968,7 @@ content into your application; rather pick only the properties that you need.
 	spring.kafka.consumer.heartbeat-interval= # Expected time in milliseconds between heartbeats to the consumer coordinator.
 	spring.kafka.consumer.key-deserializer= # Deserializer class for keys.
 	spring.kafka.consumer.max-poll-records= # Maximum number of records returned in a single call to poll().
+	spring.kafka.consumer.properties.*= # Additional properties used to configure the client.
 	spring.kafka.consumer.ssl.key-password= # Password of the private key in the key store file.
 	spring.kafka.consumer.ssl.keystore-location= # Location of the key store file.
 	spring.kafka.consumer.ssl.keystore-password= # Store password for the key store file.
@@ -991,14 +992,15 @@ content into your application; rather pick only the properties that you need.
 	spring.kafka.producer.client-id= # Id to pass to the server when making requests; used for server-side logging.
 	spring.kafka.producer.compression-type= # Compression type for all data generated by the producer.
 	spring.kafka.producer.key-serializer= # Serializer class for keys.
+	spring.kafka.producer.properties.*= # Additional properties used to configure the client.
 	spring.kafka.producer.retries= # When greater than zero, enables retrying of failed sends.
 	spring.kafka.producer.ssl.key-password= # Password of the private key in the key store file.
 	spring.kafka.producer.ssl.keystore-location= # Location of the key store file.
 	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.value-serializer= # Serializer class for values.
-	spring.kafka.properties.*= # Additional properties used to configure the client.
+	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.
 	spring.kafka.ssl.keystore-location= # Location of the key store file.
 	spring.kafka.ssl.keystore-password= # Store password for the key store file.

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

@@ -5117,20 +5117,13 @@ are not directly supported, use the following:
 [source,properties,indent=0]
 ----
 	spring.kafka.properties.foo.bar=baz
+	spring.kafka.consumer.properties.fiz.buz=qux
+	spring,kafka.producer.properties.baz.qux=fiz
 ----
 
-This sets the common `foo.bar` Kafka property to `baz`.
-
-These properties will be shared by both the consumer and producer factory beans.
-If you wish to customize these components with different properties, such as to use a
-different metrics reader for each, you can override the bean definitions, as follows:
-
-[source,java,indent=0]
-----
-include::{code-examples}/kafka/KafkaSpecialProducerConsumerConfigExample.java[tag=configuration]
-----
-
+This sets the common `foo.bar` Kafka property to `baz` (applies to both producers and consumers), the consumer `fiz.buz` property to `qux` and the `baz.qux` producer property to `fiz`.
 
+IMPORTANT: Properties set in this way will override properties that are in the subset that boot explicitly supports.
 
 [[boot-features-resttemplate]]
 == Calling REST services with '`RestTemplate`'