How to Use Kafka Producer in Java: Simple Guide

To use a KafkaProducer in Java, create a producer instance with configuration properties, then send messages to a Kafka topic using the send() method. Always close the producer after use to free resources.

Syntax

The basic syntax to create and use a Kafka producer in Java involves setting properties, creating a KafkaProducer object, and sending messages with send().

• Properties: Configure bootstrap servers and serializers.
• KafkaProducer: Instantiate with properties.
• ProducerRecord: Create message with topic, key, and value.
• send(): Send the record asynchronously.
• close(): Close the producer to release resources.

java

Properties props = new Properties();
props.put("bootstrap.servers", "localhost:9092");
props.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer");
props.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer");

KafkaProducer<String, String> producer = new KafkaProducer<>(props);

ProducerRecord<String, String> record = new ProducerRecord<>("topic-name", "key", "value");
producer.send(record);

producer.close();

Example

This example shows a complete Java program that sends a simple message to a Kafka topic named test-topic. It demonstrates setting up the producer, sending a message, and closing the producer.

java

import org.apache.kafka.clients.producer.KafkaProducer;
import org.apache.kafka.clients.producer.ProducerRecord;
import org.apache.kafka.clients.producer.RecordMetadata;
import java.util.Properties;
import java.util.concurrent.Future;

public class SimpleKafkaProducer {
    public static void main(String[] args) {
        Properties props = new Properties();
        props.put("bootstrap.servers", "localhost:9092");
        props.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer");
        props.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer");

        KafkaProducer<String, String> producer = new KafkaProducer<>(props);

        ProducerRecord<String, String> record = new ProducerRecord<>("test-topic", "myKey", "Hello Kafka");

        try {
            Future<RecordMetadata> future = producer.send(record);
            RecordMetadata metadata = future.get();
            System.out.println("Message sent to topic " + metadata.topic() + " partition " + metadata.partition() + " offset " + metadata.offset());
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            producer.close();
        }
    }
}

Output

Message sent to topic test-topic partition 0 offset 0

Common Pitfalls

Common mistakes when using Kafka producer in Java include:

• Not setting the correct bootstrap.servers address, causing connection failures.
• Forgetting to specify serializers for key and value, leading to serialization errors.
• Not closing the producer, which can cause resource leaks.
• Ignoring exceptions from send() which may hide message delivery failures.

Always handle exceptions and close the producer properly.

java

/* Wrong: Missing serializers and not closing producer */
Properties props = new Properties();
props.put("bootstrap.servers", "localhost:9092");
KafkaProducer<String, String> producer = new KafkaProducer<>(props);
producer.send(new ProducerRecord<>("topic", "key", "value"));

/* Right: Include serializers and close producer */
props.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer");
props.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer");
KafkaProducer<String, String> producerCorrect = new KafkaProducer<>(props);
try {
    producerCorrect.send(new ProducerRecord<>("topic", "key", "value"));
} finally {
    producerCorrect.close();
}

Quick Reference

Remember these key points when using Kafka producer in Java:

• Set bootstrap.servers to your Kafka broker address.
• Use StringSerializer or appropriate serializers for your data.
• Create ProducerRecord with topic, key, and value.
• Use send() to send messages asynchronously.
• Always close the producer with close() to free resources.

Key Takeaways

Always configure bootstrap servers and serializers before creating KafkaProducer.

Use ProducerRecord to specify topic, key, and message value for sending.

Handle exceptions from send() to catch delivery issues.

Close the KafkaProducer after use to avoid resource leaks.

Test connectivity to Kafka brokers before sending messages.