Polish Kafka properties

Closes gh-7672

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

@@ -33,6 +33,7 @@ import org.apache.kafka.common.serialization.StringSerializer;
 import org.springframework.boot.context.properties.ConfigurationProperties;
 import org.springframework.core.io.Resource;
 import org.springframework.kafka.listener.AbstractMessageListenerContainer.AckMode;
+import org.springframework.util.CollectionUtils;
 
 /**
  * Configuration properties for Spring for Apache Kafka.
@@ -47,18 +48,6 @@ import org.springframework.kafka.listener.AbstractMessageListenerContainer.AckMo
 @ConfigurationProperties(prefix = "spring.kafka")
 public class KafkaProperties {
 
-	private final Consumer consumer = new Consumer();
-
-	private final Producer producer = new Producer();
-
-	private final Listener listener = new Listener();
-
-	private final Template template = new Template();
-
-	private final Ssl ssl = new Ssl();
-
-	// Apache Kafka Common Properties
-
 	/**
 	 * Comma-delimited list of host:port pairs to use for establishing the initial
 	 * connection to the Kafka cluster.
@@ -76,25 +65,15 @@ public class KafkaProperties {
 	 */
 	private Map<String, String> properties = new HashMap<String, String>();
 
-	public Consumer getConsumer() {
-		return this.consumer;
-	}
+	private final Consumer consumer = new Consumer();
 
-	public Producer getProducer() {
-		return this.producer;
-	}
+	private final Producer producer = new Producer();
 
-	public Listener getListener() {
-		return this.listener;
-	}
+	private final Listener listener = new Listener();
 
-	public Ssl getSsl() {
-		return this.ssl;
-	}
+	private final Ssl ssl = new Ssl();
 
-	public Template getTemplate() {
-		return this.template;
-	}
+	private final Template template = new Template();
 
 	public List<String> getBootstrapServers() {
 		return this.bootstrapServers;
@@ -120,6 +99,26 @@ public class KafkaProperties {
 		this.properties = properties;
 	}
 
+	public Consumer getConsumer() {
+		return this.consumer;
+	}
+
+	public Producer getProducer() {
+		return this.producer;
+	}
+
+	public Listener getListener() {
+		return this.listener;
+	}
+
+	public Ssl getSsl() {
+		return this.ssl;
+	}
+
+	public Template getTemplate() {
+		return this.template;
+	}
+
 	private Map<String, Object> buildCommonProperties() {
 		Map<String, Object> properties = new HashMap<String, Object>();
 		if (this.bootstrapServers != null) {
@@ -148,7 +147,7 @@ public class KafkaProperties {
 			properties.put(SslConfigs.SSL_TRUSTSTORE_PASSWORD_CONFIG,
 					this.ssl.getTruststorePassword());
 		}
-		if (this.properties != null && this.properties.size() > 0) {
+		if (!CollectionUtils.isEmpty(this.properties)) {
 			properties.putAll(this.properties);
 		}
 		return properties;
@@ -163,9 +162,9 @@ public class KafkaProperties {
 	 * instance
 	 */
 	public Map<String, Object> buildConsumerProperties() {
-		Map<String, Object> props = buildCommonProperties();
-		props.putAll(this.consumer.buildProperties());
-		return props;
+		Map<String, Object> properties = buildCommonProperties();
+		properties.putAll(this.consumer.buildProperties());
+		return properties;
 	}
 
 	/**
@@ -177,9 +176,9 @@ public class KafkaProperties {
 	 * instance
 	 */
 	public Map<String, Object> buildProducerProperties() {
-		Map<String, Object> props = buildCommonProperties();
-		props.putAll(this.producer.buildProperties());
-		return props;
+		Map<String, Object> properties = buildCommonProperties();
+		properties.putAll(this.producer.buildProperties());
+		return properties;
 	}
 
 	private static String resourceToPath(Resource resource) {
@@ -425,7 +424,8 @@ public class KafkaProperties {
 						this.valueDeserializer);
 			}
 			if (this.maxPollRecords != null) {
-				properties.put(ConsumerConfig.MAX_POLL_RECORDS_CONFIG, this.maxPollRecords);
+				properties.put(ConsumerConfig.MAX_POLL_RECORDS_CONFIG,
+						this.maxPollRecords);
 			}
 			return properties;
 		}

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

@@ -60,8 +60,7 @@ public class KafkaAutoConfigurationTests {
 
 	@Test
 	public void consumerProperties() {
-		load("spring.kafka.bootstrap-servers=foo:1234",
-				"spring.kafka.properties.foo=bar",
+		load("spring.kafka.bootstrap-servers=foo:1234", "spring.kafka.properties.foo=bar",
 				"spring.kafka.properties.baz=qux",
 				"spring.kafka.properties.foo.bar.baz=qux.fiz.buz",
 				"spring.kafka.ssl.key-password=p1",
@@ -113,8 +112,7 @@ public class KafkaAutoConfigurationTests {
 				.isEqualTo(LongDeserializer.class);
 		assertThat(configs.get(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG))
 				.isEqualTo(IntegerDeserializer.class);
-		assertThat(configs.get(ConsumerConfig.MAX_POLL_RECORDS_CONFIG))
-				.isEqualTo(42);
+		assertThat(configs.get(ConsumerConfig.MAX_POLL_RECORDS_CONFIG)).isEqualTo(42);
 		assertThat(configs.get("foo")).isEqualTo("bar");
 		assertThat(configs.get("baz")).isEqualTo("qux");
 		assertThat(configs.get("foo.bar.baz")).isEqualTo("qux.fiz.buz");

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

@@ -4646,9 +4646,12 @@ Only a subset of the properties supported by Kafka are available via the `KafkaP
 class. If you wish to configure the producer or consumer with additional properties that
 are not directly supported, use the following:
 
-`spring.kafka.properties.foo.bar=baz`
+[source,properties,indent=0]
+----
+	spring.kafka.properties.foo.bar=baz
+----
 
-This sets the common `foo.bar` kafka property to `baz`.
+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
@@ -4659,6 +4662,8 @@ different metrics reader for each, you can override the bean definitions, as fol
 include::{code-examples}/kafka/KafkaSpecialProducerConsumerConfigExample.java[tag=configuration]
 ----
 
+
+
 [[boot-features-restclient]]
 == Calling REST services
 If you need to call remote REST services from your application, you can use Spring

spring-boot-docs/src/main/java/org/springframework/boot/kafka/KafkaSpecialProducerConsumerConfigExample.java

@@ -32,12 +32,11 @@ import org.springframework.kafka.core.DefaultKafkaProducerFactory;
 import org.springframework.kafka.core.ProducerFactory;
 
 /**
- * Example custom kafka configuration beans used when the user wants to
- * apply different common properties to the producer and consumer.
+ * Example custom kafka configuration beans used when the user wants to apply different
+ * common properties to the producer and consumer.
  *
  * @author Gary Russell
  * @since 1.5
- *
  */
 public class KafkaSpecialProducerConsumerConfigExample {
 
@@ -65,7 +64,8 @@ public class KafkaSpecialProducerConsumerConfigExample {
 		 */
 		@Bean
 		public ConsumerFactory<?, ?> kafkaConsumerFactory(KafkaProperties properties) {
-			Map<String, Object> consumererProperties = properties.buildConsumerProperties();
+			Map<String, Object> consumererProperties = properties
+					.buildConsumerProperties();
 			consumererProperties.put(CommonClientConfigs.METRIC_REPORTER_CLASSES_CONFIG,
 					MyConsumerMetricsReporter.class);
 			return new DefaultKafkaConsumerFactory<Object, Object>(consumererProperties);