Polish "Add Kafka sample"

Closes gh-11597

spring-boot-samples/README.adoc

@@ -119,6 +119,9 @@ The following sample applications are provided:
 | link:spring-boot-sample-junit-jupiter[spring-boot-sample-junit-jupiter]
 | Demonstrates JUnit Jupiter-based testing
 
+| link:spring-boot-sample-kafka[spring-boot-sample-kafka]
+| consumer and producer using Apache Kafka
+
 | link:spring-boot-sample-liquibase[spring-boot-sample-liquibase]
 | Database migrations with Liquibase
 
@@ -230,6 +233,3 @@ The following sample applications are provided:
 | link:spring-boot-sample-xml[spring-boot-sample-xml]
 | Example show how Spring Boot can be mixed with traditional XML configuration (we
   generally recommend using Java `@Configuration` whenever possible
-  
-| link:spring-boot-sample-kafka[spring-boot-sample-kafka]
-| consumer and producer using Apache Kafka

spring-boot-samples/pom.xml

@@ -57,6 +57,7 @@
 		<module>spring-boot-sample-jta-narayana</module>
 		<module>spring-boot-sample-jta-jndi</module>
 		<module>spring-boot-sample-junit-jupiter</module>
+		<module>spring-boot-sample-kafka</module>
 		<module>spring-boot-sample-liquibase</module>
 		<module>spring-boot-sample-logback</module>
 		<module>spring-boot-sample-oauth2-client</module>
@@ -97,7 +98,6 @@
 		<module>spring-boot-sample-websocket-undertow</module>
 		<module>spring-boot-sample-webservices</module>
 		<module>spring-boot-sample-xml</module>
-		<module>spring-boot-sample-kafka</module>
 	</modules>
 	<!-- No dependencies - otherwise the samples won't work if you change the
 		parent -->

spring-boot-samples/spring-boot-sample-kafka/pom.xml

@@ -20,16 +20,12 @@
 		<!-- Compile -->
 		<dependency>
 			<groupId>org.springframework.boot</groupId>
-			<artifactId>spring-boot-starter</artifactId>
+			<artifactId>spring-boot-starter-json</artifactId>
 		</dependency>
 		<dependency>
 			<groupId>org.springframework.kafka</groupId>
 			<artifactId>spring-kafka</artifactId>
 		</dependency>
-		<dependency>
-			<groupId>org.springframework.boot</groupId>
-			<artifactId>spring-boot-starter-json</artifactId>
-		</dependency>
 		<!-- Test -->
 		<dependency>
 			<groupId>org.springframework.boot</groupId>
@@ -39,6 +35,7 @@
 		<dependency>
 			<groupId>org.springframework.kafka</groupId>
 			<artifactId>spring-kafka-test</artifactId>
+			<scope>test</scope>
 		</dependency>
 	</dependencies>
 

spring-boot-samples/spring-boot-sample-kafka/src/main/java/sample/kafka/Consumer.java

@@ -19,10 +19,11 @@ import org.springframework.kafka.annotation.KafkaListener;
 import org.springframework.stereotype.Component;
 
 @Component
-public class Consumer {
+class Consumer {
 
-	@KafkaListener(topics = "myTopic")
+	@KafkaListener(topics = "testTopic")
 	public void processMessage(SampleMessage message) {
-		System.out.println("consumer has received message : [" + message + "]");
+		System.out.println("Received sample message [" + message + "]");
 	}
+
 }

spring-boot-samples/spring-boot-sample-kafka/src/main/java/sample/kafka/Producer.java

@@ -15,18 +15,21 @@
  */
 package sample.kafka;
 
-import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.kafka.core.KafkaTemplate;
 import org.springframework.stereotype.Component;
 
 @Component
 public class Producer {
 
-	@Autowired
-	private KafkaTemplate kafkaTemplate;
+	private final KafkaTemplate<Object, SampleMessage> kafkaTemplate;
+
+	Producer(KafkaTemplate<Object, SampleMessage> kafkaTemplate) {
+		this.kafkaTemplate = kafkaTemplate;
+	}
 
 	public void send(SampleMessage message) {
-		kafkaTemplate.send("myTopic", message);
-		System.out.println("producer has sent message.");
+		this.kafkaTemplate.send("testTopic", message);
+		System.out.println("Sent sample message [" + message + "]");
 	}
+
 }

spring-boot-samples/spring-boot-sample-kafka/src/main/java/sample/kafka/SampleKafkaApplication.java

@@ -15,8 +15,11 @@
  */
 package sample.kafka;
 
+import org.springframework.boot.ApplicationRunner;
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.boot.builder.SpringApplicationBuilder;
+import org.springframework.context.annotation.Bean;
 
 @SpringBootApplication
 public class SampleKafkaApplication {
@@ -24,4 +27,10 @@ public class SampleKafkaApplication {
 	public static void main(String[] args) {
 		SpringApplication.run(SampleKafkaApplication.class, args);
 	}
+
+	@Bean
+	public ApplicationRunner runner(Producer producer) {
+		return args -> producer.send(new SampleMessage(1, "A simple test message"));
+	}
+
 }

spring-boot-samples/spring-boot-sample-kafka/src/main/java/sample/kafka/SampleMessage.java

@@ -15,39 +15,37 @@
  */
 package sample.kafka;
 
-public class SampleMessage {
-	private Integer id;
-	private String message;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonProperty;
 
-	public Integer getId() {
-		return id;
+public class SampleMessage {
+
+	private final Integer id;
+
+	private final String message;
+
+	@JsonCreator
+	public SampleMessage(@JsonProperty("id") Integer id,
+			@JsonProperty("message") String message) {
+		this.id = id;
+		this.message = message;
 	}
 
-	public void setId(Integer id) {
-		this.id = id;
+	public Integer getId() {
+		return this.id;
 	}
 
 	public String getMessage() {
-		return message;
-	}
-
-	public void setMessage(String message) {
-		this.message = message;
-	}
-
-	public SampleMessage() {
-	}
-
-	public SampleMessage(Integer id, String message) {
-		this.id = id;
-		this.message = message;
+		return this.message;
 	}
 
 	@Override
 	public String toString() {
-		return "SampleMessage{" +
-				"id=" + id +
-				", message='" + message + '\'' +
-				'}';
+		final StringBuilder sb = new StringBuilder("SampleMessage{");
+		sb.append("id=").append(this.id);
+		sb.append(", message='").append(this.message).append('\'');
+		sb.append('}');
+		return sb.toString();
 	}
+
 }

spring-boot-samples/spring-boot-sample-kafka/src/main/resources/application.properties

@@ -1,5 +1,6 @@
 spring.kafka.bootstrap-servers=localhost:9092
-spring.kafka.consumer.group-id=myGroup
+spring.kafka.consumer.group-id=testGroup
+spring.kafka.consumer.auto-offset-reset=earliest
 spring.kafka.consumer.value-deserializer=org.springframework.kafka.support.serializer.JsonDeserializer
-spring.kafka.Producer.value-serializer=org.springframework.kafka.support.serializer.JsonSerializer
+spring.kafka.producer.value-serializer=org.springframework.kafka.support.serializer.JsonSerializer
 spring.kafka.consumer.properties.spring.json.trusted.packages=sample.kafka

spring-boot-samples/spring-boot-sample-kafka/src/test/java/sample/kafka/SampleKafkaApplicationTests.java

@@ -15,13 +15,20 @@
  */
 package sample.kafka;
 
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
+
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.runner.RunWith;
+
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.boot.test.context.TestConfiguration;
 import org.springframework.boot.test.rule.OutputCapture;
-import org.springframework.kafka.test.rule.KafkaEmbedded;
+import org.springframework.context.annotation.Bean;
+import org.springframework.kafka.test.context.EmbeddedKafka;
+import org.springframework.test.context.TestPropertySource;
 import org.springframework.test.context.junit4.SpringRunner;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -30,32 +37,41 @@ import static org.assertj.core.api.Assertions.assertThat;
  * Integration tests for demo application.
  *
  * @author hcxin
+ * @author Gary Russell
+ * @author Stephane Nicoll
  */
 @RunWith(SpringRunner.class)
 @SpringBootTest
+@TestPropertySource(properties = "spring.kafka.bootstrap-servers=${spring.embedded.kafka.brokers}")
+@EmbeddedKafka
 public class SampleKafkaApplicationTests {
 
+	private static final CountDownLatch latch = new CountDownLatch(1);
+
 	@Rule
 	public OutputCapture outputCapture = new OutputCapture();
 
-	@Autowired
-	private Producer producer;
-
 	@Test
-	public void sendSimpleMessage() throws Exception {
-		initKafkaEmbedded();
-		SampleMessage message = new SampleMessage(1, "Test message");
-		producer.send(message);
-		Thread.sleep(1000L);
-		assertThat(this.outputCapture.toString().contains("Test message")).isTrue();
+	public void testVanillaExchange() throws Exception {
+		assertThat(latch.await(10, TimeUnit.SECONDS)).isTrue();
+		assertThat(this.outputCapture.toString().contains("A simple test message"))
+				.isTrue();
 	}
 
-	public void initKafkaEmbedded() throws Exception {
-		KafkaEmbedded embeddedKafka = new KafkaEmbedded(1, true);
-		embeddedKafka.setKafkaPorts(9092);
-		embeddedKafka.afterPropertiesSet();
-		//Need 10s, waiting for the Kafka server start.
-		Thread.sleep(10000L);
+	@TestConfiguration
+	public static class Config {
+
+		@Bean
+		public Consumer consumer() {
+			return new Consumer() {
+				@Override
+				public void processMessage(SampleMessage message) {
+					super.processMessage(message);
+					latch.countDown();
+				}
+			};
+		}
 
 	}
+
 }