Kafka message queue is simple to use

The following is a simple example of implementing a message queue using Spring Boot and Kafka:

1. Introduce dependencies

Add the following dependencies in pom.xml:

<dependency>
    <groupId>org.springframework.kafka</groupId>
    <artifactId>spring-kafka</artifactId>
    <version>2.7.5</version>
</dependency>

1. Place Kafka

Add Kafka related configuration in application.properties:

spring.kafka.bootstrap-servers=localhost:9092
spring.kafka.consumer.group-id=myGroup
spring.kafka.producer.key-serializer=org.apache.kafka.common.serialization.StringSerializer
spring.kafka.producer.value-serializer=org.apache.kafka.common.serialization.StringSerializer
spring.kafka.consumer.key-deserializer=org.apache.kafka.common.serialization.StringDeserializer
spring.kafka.consumer.value-deserializer=org.apache.kafka.common.serialization.StringDeserializer

1. Send a message

Create a producer class and use KafkaTemplate to send messages:

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

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

1. receive messages

Create a consumer class, use the @KafkaListener annotation to listen to the specified topic and process messages:

@Service
public class KafkaConsumerService {
    @KafkaListener(topics = "myTopic", groupId = "myGroup")
    public void onMessage(String message) {
        System.out.println("Received message: " + message);
    }
}

1. test

Call the producer in the Controller to send the message, and then you can see the message received by the consumer in the console:

@RestController
public class KafkaController {
    @Autowired
    private KafkaProducerService kafkaProducerService;

    @GetMapping("/send")
    public String sendMessage() {
        kafkaProducerService.sendMessage("myTopic", "Hello, Kafka!");
        return "Message sent successfully";
    }
}

The above is a simple example of using Spring Boot and Kafka to implement a message queue.

Partition

1. Write Kafka producer code, use KafkaTemplate to send messages, and specify the partition number. As follows:

@Autowired
private KafkaTemplate<String, String> kafkaTemplate;

public void sendMessage(String message, int partition) {
    kafkaTemplate.send("my-topic", partition, null, message);

2. Write Kafka consumer code, use the @KafkaListener annotation to listen to the specified topic, and obtain the partition number in the method parameters. As follows:

@KafkaListener(topics = "my-topic", groupId = "my-group")
public void listen(ConsumerRecord<String, String> record, @Header(KafkaHeaders.RECEIVED_PARTITION_ID) int partition) {
    System.out.println("Received message: " + record.value() + ", partition: " + partition);