Spring Boot Kafka Microservices - #10 - Create Kafka Producer in OrderService Microservice

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Welcome to Spring Boot Kafka Event-Driven Microservices Series. In this lecture, we will Create Kafka Producer in OrderService Microservice.

Lecture - #10 - Create Kafka Producer in OrderService Microservice

Source Code used in Lecture for Your Reference

Create Kafka Producer in OrderService Microservice

In an order-service project, create a package named Kafka. Within a Kafka package, create a class named OrderProducer and add the following content to it:

package net.javaguides.orderservice.kafka;

import net.javaguides.basedomains.dto.OrderEvent;
import org.apache.kafka.clients.admin.NewTopic;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.kafka.core.KafkaTemplate;
import org.springframework.kafka.support.KafkaHeaders;
import org.springframework.messaging.Message;
import org.springframework.messaging.support.MessageBuilder;
import org.springframework.stereotype.Service;

@Service
public class OrderProducer {

    private static final Logger LOGGER = LoggerFactory.getLogger(OrderProducer.class);

    private NewTopic topic;

    private KafkaTemplate<String, OrderEvent> kafkaTemplate;

    public OrderProducer(NewTopic topic, KafkaTemplate<String, OrderEvent> kafkaTemplate) {
        this.topic = topic;
        this.kafkaTemplate = kafkaTemplate;
    }

    public void sendMessage(OrderEvent event){
        LOGGER.info(String.format("Order event => %s", event.toString()));

        // create Message
        Message<OrderEvent> message = MessageBuilder
                .withPayload(event)
                .setHeader(KafkaHeaders.TOPIC, topic.name())
                .build();
        kafkaTemplate.send(message);
    }
}

Note that we are sending an OrderEvent object to a Kafka Topic.

We created a KafkaTemplate<String, OrderEvent> since we are sending Java Objects to the Kafka topic that’ll automatically be transformed into a JSON byte[].

In this example, we created a Message using the MessageBuilder. It’s important to add the topic to which we are going to send the message too.

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