Lab
A Cloud Guru

Connecting to Kafka Programmatically in Java

The real power of Kafka comes from the ability to write applications that utilize it. Kafka's Java APIs make it easy to build applications that work with Kafka data. Through this lab, we will have the opportunity to build a simple Java program that consumes data from a Kafka topic. Tackling this challenge will provide hands-on experience with the Kafka Java APIs and consuming data from a real cluster. After completing this introductory lab, we will be ready to move on to more complex scenarios involving both Kafka and Java code.

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Path Info

Level

Intermediate

Duration

1h 15m

Published

Oct 04, 2019

Challenge

Clone the Starter Project from GitHub and Perform a Test Run
1. Clone the starter project from GitHub.
```
cd ~/
git clone https://github.com/linuxacademy/content-ccdak-kafka-simple-consumer.git
```
1. Perform a test to make sure the code is able to compile and run.
```
cd content-ccdak-kafka-simple-consumer/
./gradlew run
```
The output should contain the message printed by the Main class: Hello, world!.

Challenge

Implement a Consumer in the Main Class and Run It

Add the Kafka Client Libraries as a project dependency in build.gradle with:

vi build.gradle

In the dependencies { ... } block, add the following line:

implementation 'org.apache.kafka:kafka-clients:2.2.1'

Edit the Main class:

vi src/main/java/com/linuxacademy/ccdak/kafkaSimpleConsumer/Main.java

Implement a basic consumer that consumes messages from the topic and prints them to the screen:

package com.linuxacademy.ccdak.kafkaSimpleConsumer;

import org.apache.kafka.clients.consumer.*;
import java.util.Properties;
import java.util.Arrays;
import java.time.Duration;

public class Main {

    public static void main(String[] args) {
        Properties props = new Properties();
        props.setProperty("bootstrap.servers", "localhost:9092");
        props.setProperty("group.id", "my-group");
        props.setProperty("enable.auto.commit", "true");
        props.setProperty("auto.commit.interval.ms", "1000");
        props.setProperty("key.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
        props.setProperty("value.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
        KafkaConsumer<String, String> consumer = new KafkaConsumer<String, String>(props);
        consumer.subscribe(Arrays.asList("inventory_purchases"));
        while (true) {
            ConsumerRecords<String, String> records = consumer.poll(Duration.ofMillis(100));
            for (ConsumerRecord<String, String> record : records) {
                System.out.printf("offset = %d, key = %s, value = %s%n", record.offset(), record.key(), record.value());
            }
        }
    }

}

Run the code:

./gradlew run

The program should print a series of messages from the Kafka topic containing information about item purchases.

Author

A Cloud Guru

The Cloud Content team comprises subject matter experts hyper focused on services offered by the leading cloud vendors (AWS, GCP, and Azure), as well as cloud-related technologies such as Linux and DevOps. The team is thrilled to share their knowledge to help you build modern tech solutions from the ground up, secure and optimize your environments, and so much more!

What's a lab?

Hands-on Labs are real environments created by industry experts to help you learn. These environments help you gain knowledge and experience, practice without compromising your system, test without risk, destroy without fear, and let you learn from your mistakes. Hands-on Labs: practice your skills before delivering in the real world.