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Develop with Java Kafka client

This page shows how to use Apache Kafka Java Client to interact with HStream.

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Replace the variables in the following code according to your setup.

Create a Topic

java
import java.util.Collections;
import java.util.Properties;
import org.apache.kafka.clients.admin.AdminClient;
import org.apache.kafka.clients.admin.NewTopic;

class CreateTopic {
  public static void main(String[] args) throws Exception {
    String endpoint = "localhost:9092";
    String topicName = "my_topic";
    int partitions = 1;
    short replicationFactor = 1;

    var props = new Properties();
    props.put("bootstrap.servers", endpoint);

    try (var admin = AdminClient.create(props)) {
      admin
          .createTopics(
              Collections.singleton(new NewTopic(topicName, partitions, replicationFactor)))
          .all()
          .get();
    }
  }
}

Produce a Record

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

class Produce {
  public static void main(String[] args) throws Exception {
    String endpoint = "localhost:9092";
    String topicName = "my_topic";

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

    try (var producer = new KafkaProducer<String, String>(props)) {
      producer.send(new ProducerRecord<>(topicName, "Hello HStream!"));
      producer.flush();
    }
  }
}

Consume Records

java
import java.time.Duration;
import java.util.Collections;
import java.util.Properties;
import org.apache.kafka.clients.consumer.KafkaConsumer;

class Consume {
  public static void main(String[] args) throws Exception {
    String endpoint = "localhost:9092";
    String topicName = "my_topic";
    String groupName = "my_group";

    var props = new Properties();
    props.put("bootstrap.servers", endpoint);
    props.put("key.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
    props.put("value.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
    props.put("auto.offset.reset", "earliest");
    props.put("group.id", groupName);

    try (var consumer = new KafkaConsumer<String, String>(props)) {
      consumer.subscribe(Collections.singleton(topicName));
      var records = consumer.poll(Duration.ofSeconds(10));
      for (var record : records) {
        System.out.println(record);
      }
    }
  }
}