Spring Boot + Apache Kafka Hello World Example

In this post we will integrate Spring Boot and Apache Kafka instance.
In a previous post we had seen how to get Apache Kafka up and running.

RabbitMQ - Table Of Contents
What is Apache Kafka
Understanding Apache Kafka Architecture
Internal Working Of Apache Kafka
Getting Started with Apache Kafka - Hello World Example
Spring Boot + Apache Kafka Example

Lets Begin-

The project will be as follows-

Define the pom.xml as follows- Add the spring-kafka dependency.

<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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.javainuse</groupId>
  <artifactId>SpringBootApacheKafkaHelloWorld</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  
  <packaging>jar</packaging>


	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>1.5.3.RELEASE</version>
		<relativePath/>
	</parent>

	<properties>
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
		<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
		<java.version>1.8</java.version>
	</properties>

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

Define the KafkaSender class to send message to the kafka topic named as java_in_use-topic.

package com.javainuse.service;

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

@Service
public class KafkaSender {
	
	@Autowired
	private KafkaTemplate<String, String> kafkaTemplate;
	
	String kafkaTopic = "java_in_use_topic";
	
	public void send(String message) {
	    
	    kafkaTemplate.send(kafkaTopic, message);
	}
}

Define a Controller which will pass the message and trigger the send message to the Kafka Topic using the KafkaSender class.

package com.javainuse.controller;

import org.springframework.beans.factory.annotation.Autowired;
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;

import com.javainuse.service.KafkaSender;

@RestController
@RequestMapping(value = "/javainuse-kafka/")
public class ApacheKafkaWebController {

	@Autowired
	KafkaSender kafkaSender;

	@GetMapping(value = "/producer")
	public String producer(@RequestParam("message") String message) {
		kafkaSender.send(message);

		return "Message sent to the Kafka Topic java_in_use_topic Successfully";
	}

}

Finally Define the Spring Boot Class with @SpringBootApplication annotation

package com.javainuse;

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

@SpringBootApplication
public class SpringBootHelloWorldApplication {

	public static void main(String[] args) {

		SpringApplication.run(
				new Object[] { SpringBootHelloWorldApplication.class }, args);
	}
}

We are done with the required Java code. Now lets start Apache Kafka. As we had explained in detail in the Getting started with Apache Kafka perform the following.

• Start Apache Zookeeper-

  C:\kafka_2.12-0.10.2.1>.\bin\windows\zookeeper-server-start.bat .\config\zookeeper.properties
  

  
  
  
  
• Start Apache Kafka-

  C:\kafka_2.12-0.10.2.1>.\bin\windows\kafka-server-start.bat .\config\server.properties
  

  
  
  
• Next start the Spring Boot Application by running it as a Java Application.
• Also Start the consumer listening to the java_in_use_topic-

  C:\kafka_2.12-0.10.2.1>.\bin\windows\kafka-console-consumer.bat --bootstrap-server localhost:9092 --topic java_in_use_topic --from-beginning
  

  
  
  
• Finally hit the url as follows- http://localhost:8080//javainuse-kafka/producer?message=test
  
  
• This will trigger the message to be sent to the java_in_use_topic. We can see in the consumer started the message is recieved.
  
  

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Spring Boot + Apache Kafka Hello World Example