Spring Boot + Kafka - Producer and Consumer Example

 In this section, we will learn how to do asynchronous communication using Kafka in Spring Boot application.

We will develop two Spring Boot applications, one producer and one consumer application, then we will learn how to use Kafka in the Spring boot application to send and receive messages between the Producer and the Consumer.

In the digital world, different systems are constantly sending or receiving messages. This must be carried out in a controlled manner so that messages do not block each other, end up creating a jam and processes cannot function optimally. In order for applications to be able to communicate with each other easily, it makes sense to create an intermediary, that is, a service that is responsible for managing the distribution of messages: this is what is known as a messaging broker. Kafka, one of the best known.

1. What we will build?

We will develop two Spring Boot applications, one producer and one consumer application, then we will learn how to use Kafka in the Spring boot application to send and receive messages between the Producer and the Consumer.

The following diagram is an overview of the components in our messaging system.


2.Key terminologies of Kafka:

  • Producer: A producer is a client that sends messages to the Kafka server to the specified topic. 
  • Consumer: Consumers are the recipients who receive messages from the Kafka server. 
  • Broker: Brokers can create a Kafka cluster by sharing information using Zookeeper. A broker receives messages from producers and consumers fetch messages from the broker by topic, partition, and offset. 
  • Cluster: A Kafka cluster is a system that consists of several Brokers, Topics, and Partitions for both. 
  • Topic: Kafka topics are the categories used to organize messages. Each topic has a name that is unique across the entire Kafka cluster. Messages are sent to and read from specific topics. In other words, producers write data to topics, and consumers read data from topics. 

When working with Apache Kafka, ZooKeeper is primarily used to track the status of nodes in the Kafka cluster and maintain a list of Kafka topics and messages.


3. Install and Setup Apache Kafka

  • Extract Kafka zip in the local file system
  • Start Zookeeper service. Use the below command to start the Zookeeper service:
.\bin\windows\zookeeper-server-start.bat .\config\zookeeper.properties
  • Start Kafka Broker. Open another terminal session and run the below command to start the Kafka broker:
.\bin\windows\kafka-server-start.bat .\config\server.properties
Once all services have successfully launched, you will have a basic Kafka environment running and ready to use.
Note: If you are getting error while run the command please refer this link - click here

4. Creating spring boot consumer application

First, open the Spring initializr https://start.spring.io/ 
Then, Provide the Group and Artifact name. We have provided Group name com.knf.dev.demo and Artifact consumer. Here I selected the Maven project - language Java 17 - Spring Boot 3.1.5 , and Spring for Apache Kafka.


Then, click on the Generate button. When we click on the Generate button, it starts packing the project in a .zip(consumer) file and downloads the project. Then, Extract the Zip file. 

Then, import the project on your favourite IDE.

Final Project directory:


Complete pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" 
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 
   https://maven.apache.org/xsd/maven-4.0.0.xsd">
   <modelVersion>4.0.0</modelVersion>
   <parent>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-parent</artifactId>
      <version>3.1.5</version>
      <relativePath/> <!-- lookup parent from repository -->
   </parent>
   <groupId>com.knf.dev.demo</groupId>
   <artifactId>consumer</artifactId>
   <version>0.0.1-SNAPSHOT</version>
   <name>consumer</name>
   <description>Demo project for Spring Boot</description>
   <properties>
      <java.version>17</java.version>
   </properties>
   <dependencies>
      <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter</artifactId>
      </dependency>
      <dependency>
         <groupId>org.springframework.kafka</groupId>
         <artifactId>spring-kafka</artifactId>
      </dependency>

      <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-test</artifactId>
         <scope>test</scope>
      </dependency>
      <dependency>
         <groupId>org.springframework.kafka</groupId>
         <artifactId>spring-kafka-test</artifactId>
         <scope>test</scope>
      </dependency>
   </dependencies>

   <build>
      <plugins>
         <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
         </plugin>
      </plugins>
   </build>

</project>

application.yaml

You can then configure kafka properties according to the Documentation - scroll down to the kafka properties...

Then, specify bootstrap-servers, key-serializer, value-serializer, topic name, and group.

spring:
  kafka:
    producer:
      bootstrap-servers: localhost:9092
      key-serializer: org.apache.kafka.common.serialization.StringSerializer
      value-serializer: org.apache.kafka.common.serialization.StringSerializer
kafka:
  topic:
    name: knowledgeFactory_Topic
    group: knowledgeFactory_group


Create Consumer

Consumer is  the service that will be responsible for reading messages and processing them according to the needs of your own business logic. @KafkaListener allows a method to consume messages from Kafka topic(s).

package com.knf.dev.demo.consumer.service;

import org.springframework.kafka.annotation.KafkaListener;
import org.springframework.stereotype.Service;

@Service
public class Consumer {

    @KafkaListener(topics = {"${kafka.topic.name}"}, groupId = "${kafka.topic.name}")
    public void listenToTopic(String message)
    {
        System.out.println("Message arrived! Message: " + message);
    }
}


ConsumerApplication.java

package com.knf.dev.demo.consumer;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class ConsumerApplication {

   public static void main(String[] args) {
      SpringApplication.run(ConsumerApplication.class, args);
   }

}

5. Creating spring boot producer application

First, open the Spring initializr https://start.spring.io/ 

Then, Provide the Group and Artifact name. We have provided Group name com.knf.dev.demo and Artifact producer. Here I selected the Maven project - language Java 17 - Spring Boot 3.1.5 and add Spring Web, and Spring for Apache Kafka. 

Then, click on the Generate button. When we click on the Generate button, it starts packing the project in a .zip(producer) file and downloads the project. Then, Extract the Zip file. Then, import the project on your favourite IDE.

Final Project directory:


Complete pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" 
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 
   https://maven.apache.org/xsd/maven-4.0.0.xsd">
   <modelVersion>4.0.0</modelVersion>
   <parent>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-parent</artifactId>
      <version>3.1.5</version>
      <relativePath/> <!-- lookup parent from repository -->
   </parent>
   <groupId>com.knf.dev.demo</groupId>
   <artifactId>producer</artifactId>
   <version>0.0.1-SNAPSHOT</version>
   <name>producer</name>
   <description>Demo project for Spring Boot</description>
   <properties>
      <java.version>17</java.version>
   </properties>
   <dependencies>
      <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-web</artifactId>
      </dependency>
      <dependency>
         <groupId>org.springframework.kafka</groupId>
         <artifactId>spring-kafka</artifactId>
      </dependency>

      <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-test</artifactId>
         <scope>test</scope>
      </dependency>
      <dependency>
         <groupId>org.springframework.kafka</groupId>
         <artifactId>spring-kafka-test</artifactId>
         <scope>test</scope>
      </dependency>
   </dependencies>

   <build>
      <plugins>
         <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
         </plugin>
      </plugins>
   </build>

</project>

application.yaml

Add the following configuration to application.yaml file:

spring:
  kafka:
    producer:
      bootstrap-servers: localhost:9092
      key-serializer: org.apache.kafka.common.serialization.StringSerializer
      value-serializer: org.apache.kafka.common.serialization.StringSerializer
kafka:
  topic:
    name: knowledgeFactory_Topic

Create Producer

Creating a producer will write our messages on the topic. KafkaTemplate is a class that is part of the Spring to produce messages into the Kafka Topics.

package com.knf.dev.demo.producer.service;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.kafka.core.KafkaTemplate;
import org.springframework.stereotype.Service;

@Service
public class Producer {

    KafkaTemplate<String,String> kafkaTemplate;

    @Value("${kafka.topic.name}")
    private String topic;

    public Producer(KafkaTemplate<String, String> kafkaTemplate) {
        this.kafkaTemplate = kafkaTemplate;
    }

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

Create MessageController

package com.knf.dev.demo.producer.controller;

import com.knf.dev.demo.producer.service.Producer;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("/api/v1")
public class MessageController {

    Producer producer;

    public MessageController(Producer producer) {
        this.producer = producer;
    }

    @GetMapping("/sendMessage")
    public String publishMessage(@RequestParam("message") String message) {

        producer.sendMessageToTopic(message);
        return "Message was sent successfully";
    }
}

ProducerApplication.java

package com.knf.dev.demo.producer;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class ProducerApplication {

   public static void main(String[] args) {
      SpringApplication.run(ProducerApplication.class, args);
   }

}

6. Verify our system is working as expected

First start the producer application, then start the consumer application:


Run the Spring Boot application - mvn spring-boot:run


OR 


Run this Spring boot application from 

  • IntelliJ IDEA IDE by right click - Run 'Application.main()' 
  • Eclipse/STS - You can right click the project or the Application.java file and run as java application or Spring boot application.

Open a Postman or any other tool and send a message to the producer:

The console of the consumer application now prints:

Popular posts from this blog

Learn Java 8 streams with an example - print odd/even numbers from Array and List

Example 1: Java 8 program to print odd numbers from a List   import java.util.Arrays; import java.util.List; import java.util.stream.Collectors; /*Java 8 Program to find Odd Numbers from a List*/ public class DriverClass { public static void main( String [] args) { List < Integer > numbers = Arrays. asList( 1 , 4 , 8 , 40 , 11 , 22 , 33 , 99 ); List < Integer > oddNumbers = numbers.stream(). filter(o -> o % 2 != 0 ). collect(Collectors.toList()); System.out.println(oddNumbers); } } 1. Initialize List using Arrays.asList() method. Java's built-in Arrays.asList() method converts an array into a list. This method takes an array as an argument and returns a List object. 2.  Java List interface provides stream() method which returns a sequential Stream with list of Integer as its source. 3. The Java stream filter() method allow
Read more

Java Stream API - How to convert List of objects to another List of objects using Java streams?

Image
In this section, we will show you how to convert a List of objects to another List of objects in Java using the Java streams map(). The ‘map’ method maps each element to its corresponding result. Java Stream API   The Java Stream API provides a functional programming approach over the object oriented capabilities of Java. It is used for processing collections of objects. The Stream in Java can be defined as a sequence of elements from a source List, Set or Array. Most of the stream operations return a Stream. This avails engender a chain of stream operations(stream pipe-lining). The streams withal support the aggregate or terminal operations on the elements. for example, finding the sum or maximum element or finding the average etc...Stream operations can either be executed sequentially or parallel. when performed parallelly, it is called a parallel stream.   Stream map() Method   The Java 8 Stream map() is an intermediate operation. It converts Stream<obj1> to Stream<obj2>
Read more

Registration and Login with Spring Boot + Spring Security + Thymeleaf

Image
In this section, we will learn how to create user registration and login using Spring boot, Spring security, Thymeleaf, JPA, and H2DB. The GitHub repository link is provided at the end of this tutorial. You can download the source code. Technologies used: Spring Boot 2.5.5  Spring Data JPA  Spring Security  Thymeleaf  Maven 3+  Java 17  H2 Database   User Interface User Registration Authentication Failed Authentication success Sign out Final Project Structure: Complete pom.xml: <? xml version ="1.0" encoding ="UTF-8" ?> < project xmlns ="http://maven.apache.org/POM/4.0.0" xmlns: xsi ="http://www.w3.org/2001/XMLSchema-instance" xsi :schemaLocation ="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd" > < modelVersion >4.0.0</ modelVersion > < parent > < groupId >org.springframework.boot</ groupId > < artifactId >spring-boot-starter-pare
Read more

Java, Spring Boot Mini Project - Library Management System - Download

Image
Hello everyone, Hope you are doing well. Here, we provide a Library Management System mini-project for beginners, it's free for download. Maybe you can build more on top of this project and create your own product, that's all about you. The source code download link is provided at the end of this post. 1. Benefit of this project You could cover the following technologies and features by learning and debugging this mini project. Java 17 Java Stream Java Lamda Expressions Java Records Functional programming Object-oriented programming var Keyword in Java Generics in Java Java Switch Spring boot 2.6.4 Spring Security Thymeleaf template engine OpenCSV Spring Data JPA Server Side Pagination H2 Database  Bootstrap HTML CSS and more... 2. Objective Of Spring Boot On Library Management System The main objective of this project is to manage the details of the books, author, category, and publisher. Only Admin/Librarian will manage all these activities. Also, they can export the data in
Read more

ReactJS, Spring Boot JWT Authentication Example

Image
In this tutorial, we’ll create a user registration & login example using ReactJS, Spring Boot, Spring Security, and JWT authentication. You could download the source code from our Github repository, the download link is provided at the end of this tutorial. Technologies used Backend Technologies: Java 17 Spring Boot 2.7.0 Spring Security Spring Data JPA JWT H2 Database Frontend Technologies: React 17.0.1 Axios 0.27.2 Redux 4.0.5 Bootstrap 4.5.2 ReactJS - SpringBoot - JWT - Flow Backend Project Directory: Frontend Project Directory: Following is the screenshot of our application - User Registration: User Signin: Profile View: Access Resource: We will build two projects:  1. Backend:   spring-boot-security-jwt 2. Frontend: react-redux-jwt Project 1: spring-boot-security-jwt Pom.xml <?xml version = "1.0" encoding = "UTF-8" ?> <project xmlns = "http://maven.apache.org/POM/4.0.0" xmlns:xsi = "http://www.w3.org/2001/XMLSchema-instance"
Read more

Top 5 Java ORM tools - 2024

Image
  The term ORM refers to object-relational mapping, which uses objects to adapt programming languages to database systems while allowing them to function with SQL and object-oriented programming ideas. Any kind of database management system that can accomplish object mapping to the table in the virtual system is suitable for the implementation of ORM. Java has a wide variety of ORM tools, some of which are mentioned below: 1. Hibernate Hibernate is a lightweight, open-source, non-invasive Java ORM (Object-Relational Mapping) framework that allows developers to create objects that function independently of database software and create persistence logic in any Java or JavaEE application. It offers an abstraction layer, so developers don't have to bother about implementations; Hibernate handles these tasks internally, such as connecting to databases and creating queries to carry out CRUD operations, among other things. Persistence logic development is done with it. Persistence logic r
Read more

Java - Blowfish Encryption and decryption Example

Image
Blowfish is an encryption method developed by Bruce Schneier in 1993 as an alternative to the DES encryption method. It is significantly faster than DES and provides good encryption speed, although no effective cryptanalysis technique has been found to date. It is one of the first secure block ciphers that is not protected by any patents and is therefore freely available for anyone to use. This is a symmetric block cipher algorithm. Block size: 64 bits Key size: variable size from 32 to 448 bits number of subsections: 18 [P-array] number of rounds: 16 number of substitution blocks: 4 [each with 512 records of 32 bits each] develop  Example 1: Encryption and decryption using Blowfish import java.io.UnsupportedEncodingException; import java.nio.charset.Charset; import java.security.InvalidKeyException; import java.security.NoSuchAlgorithmException; import java.util.Base64; import javax.crypto.BadPaddingException; import javax.crypto.Cipher; import javax.crypto.IllegalBlockSizeExc
Read more

Spring boot video streaming example-HTML5

Image
Hello everyone, Today we will learn how to stream MP4 video using Spring Boot and Spring Web Flux.  The Source code download link is provided at the end of this post. New, Quarkus Practice User Interface   Project Structure: G radle(build.gradle) plugins { id 'org.springframework.boot' version '2.5.4' id 'io.spring.dependency-management' version '1.0.11.RELEASE' id 'java' } group = 'com.knf.demo' version = '0.0.1-SNAPSHOT' sourceCompatibility = '11' repositories { mavenCentral() } dependencies { implementation 'org.springframework.boot:spring-boot-starter-webflux' testImplementation 'org.springframework.boot:spring-boot-starter-test' testImplementation 'io.projectreactor:reactor-test' } test { useJUnitPlatform() } Service (VideoStreamingService.java) package  com.knf.demo.service ; import org.springframework.beans.factory.annotation. Autowired ; import org.springframework
Read more

Google Cloud Storage + Spring Boot - File Upload, Download, and Delete

Image
In this section, we will learn  how to  create a simple spring boot application to perform different file operations such as upload, download, list, and delete files from the Google Cloud Storage. 1.  A little bit of Background Google Cloud Storage Cloud Storage is a managed service for storing unstructured data. Store any amount of data and retrieve it as often as you like. More Info - click here! Spring Boot Spring Boot makes it easy to create stand-alone, production-grade Spring-based Applications that you can "just run".  More Info - click here! 2. Create a GCP Project First, Sign into the Google console at  https://console.cloud.google.com . You can create a new project by first selecting the project dropdown in the top left and selecting " New Project ". Next, specify your GCP  Project name  and  Project ID . Then  Click on the " CREATE " button. Copy " Project ID " and keep it for future purposes. 3. Create a Google Cloud Storage bucket Fr
Read more