Nanditha Vuppunuthula

Posted on Jun 13

Apache Kafka and Spring Boot: A Simple Example

#kafka #springboot

Part 1: Install and Run Kafka on Windows

Prerequisites

Java 8+

Kafka 3.x (includes Zookeeper)

A terminal like Command Prompt, Git Bash, or PowerShell

Step 1: Download Kafka

Go to: https://kafka.apache.org/downloads

Choose a binary (e.g., Kafka 3.6.0 with Scala 2.13)

Extract it to C:\kafka

Step 2: Start Zookeeper

Kafka uses Zookeeper for managing brokers. In a terminal:

cd C:\kafka bin\windows\zookeeper-server-start.bat config\zookeeper.properties
Keep this terminal open.

Step 3: Start Kafka Server

Open a new terminal:

cd C:\kafka bin\windows\kafka-server-start.bat config\server.properties
Kafka is now running on localhost:9092.

Part 2: Kafka Commands

Create a Topic

bin\windows\kafka-topics.bat --create --topic test-topic --bootstrap-server localhost:9092 --partitions 1 --replication-factor 1

Check the Topic

bin\windows\kafka-topics.bat --list --bootstrap-server localhost:9092

Part 3: Spring Boot Kafka Project

Step 1: Create a Spring Boot Project

You can use Spring Initializr with the following settings:

Dependencies: Spring Web, Spring for Apache Kafka

Name: kafka-demo

Package: com.example.kafkademo

Project Structure

src/
└── main/
├── java/com/example/kafkademo/
│ ├── KafkaDemoApplication.java
│ ├── config/KafkaConfig.java
│ ├── controller/MessageController.java
│ ├── service/KafkaProducerService.java
│ └── listener/KafkaConsumerListener.java
└── resources/
└── application.yml
🛠 application.yml
spring: kafka: bootstrap-servers: localhost:9092 consumer: group-id: my-group auto-offset-reset: earliest key-deserializer: org.apache.kafka.common.serialization.StringDeserializer value-deserializer: org.apache.kafka.common.serialization.StringDeserializer producer: key-serializer: org.apache.kafka.common.serialization.StringSerializer value-serializer: org.apache.kafka.common.serialization.StringSerializer

KafkaProducerService.java

@Service
public class KafkaProducerService {
    @Autowired
    private KafkaTemplate<String, String> kafkaTemplate;

    public void sendMessage(String message) {
        kafkaTemplate.send("test-topic", message);
    }
}

KafkaConsumerListener.java

@Component
public class KafkaConsumerListener {
    @KafkaListener(topics = "test-topic", groupId = "my-group")
    public void listen(String message) {
        System.out.println("Received Message: " + message);
    }
}

MessageController.java

@RestController
@RequestMapping("/api/messages")
public class MessageController {

    @Autowired
    private KafkaProducerService producerService;

    @PostMapping
    public ResponseEntity<String> sendMessage(@RequestBody String message) {
        producerService.sendMessage(message);
        return ResponseEntity.ok("Message sent to Kafka");
    }
}

Main Application

@SpringBootApplication
public class KafkaDemoApplication {
    public static void main(String[] args) {
        SpringApplication.run(KafkaDemoApplication.class, args);
    }
}

Part 4: Run and Test

Run the App

./mvnw spring-boot:run

Test with Postman or Curl

curl -X POST http://localhost:8080/api/messages -H "Content-Type: text/plain" -d "Hello Kafka!"## Output
Your consumer will show:

Received Message: Hello Kafka!

Part 5: Clean Up

Stop the Spring Boot app --> Ctrl+C

Stop Kafka and Zookeeper --> Ctrl+C (Ctrl+C in each terminal)

Conclusion

You’ve just created a complete Kafka setup with:

A running Kafka instance on Windows

A Spring Boot REST API to send messages

A Kafka listener to consume them

DEV Community