What is event driven architecture?

If you're brand new to Kafka, be sure to check out this <a id=0 href='https://www.stackchief.com/blog/Kafka%20Architecture%20Explained'>intro to Kafka architecture</a> first.

<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">

<groupId>org.springframework.boot</groupId>

<artifactId>spring-boot-starter-parent</artifactId>

<description>Demo project for Spring Boot</description>

<groupId>org.springframework.boot</groupId>

<artifactId>spring-boot-starter</artifactId>

<groupId>org.springframework.kafka</groupId>

<groupId>com.fasterxml.jackson.core</groupId>

<artifactId>jackson-databind</artifactId>

<artifactId>spring-boot-starter-test</artifactId>

<artifactId>spring-kafka-test</artifactId>

<groupId>org.springframework.boot</groupId>

<artifactId>spring-boot-maven-plugin</artifactId>

The pom.xml defines the dependencies we need for our Maven build. Notice how we include the dependencies needed for Spring Boot along with those needed for running and testing Kafka.

Note that the jackson-databind dependency is included to account for bugs in older versions of the Spring Kafka library. You may not need to include this depending on which version of Kafka you're using..

	public static void main(String[] args) {

		SpringApplication.run(DemoApplication.class, args);

The DemoApplication.java class runs our Spring Boot application.

Spring Boot automatically configures Kafka via @SpringBootApplication. With this annotation, Spring provides/configures a KafkaAutoConfiguration class for you.

import org.springframework.kafka.annotation.KafkaListener;

import org.springframework.stereotype.Component;

    public void processMessage(String content){

        System.out.println("Message received: " + content);

The Consumer.java class is what actually listens for messages. Notice how we specify the topics to listen to within the @KafkaListener annotation.

By simply using the annotations provided by the Spring Boot Kafka library, we are able to easily set up a consumer for a given topic.

spring.kafka.bootstrap-servers=localhost:9092

Thanks to auto-configuration, you only need to define a few things in application.properties to configure the consumer. Notice how our app is configured to use Kafka locally.

This example is configured to consume from a local Kafka topic.  You'll need to have Kafka installed and running locally to see messages being consumed from the Spring Boot app.

To start Kafka locally, you need to start both the Zookeeper and Kafka servers locally...

./zookeeper-server-start /usr/local/etc/kafka/zookeeper.properties

This will start the zookeeper server with the default configurations.  Please note the path to your local Kafka install may vary.

./kafka-server-start /usr/local/etc/kafka/server.properties 

This will start the Kafka server with the default configurations.  Please note the path to your local Kafka install may vary.

To test the application consumer, you'll need to produce some messages for the test topic.  To start a Kafka console producer:

./kafka-console-producer --bootstrap-server=localhost:9092 --topic test

This starts a Kafka producer for the test topic. Notice how both the bootstrap-server and topic arguments match what we've defined in our application.properties file.

Once the producer is up and running, you can send a message to the test topic like this:

If everything is working correctly, you should see the message being logged through the Spring application like this:

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i still prefer the Promise myself.  It's just easier to understand and work with (and native to JavaScript at this point).

When you say something like "An Observable can do everything a Promise can but not the other way around"....you should be saying "both can be used to achieve the same async activity in JavaScript

The Promise is still relevant and great for async operations where you are only concerned with the result of one async operation.  While the observable handles this well with Angular, it's still perfectly reasonable to use the Promise library for http requests, etc.

stackchief

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The difference between heap and stack is how the memory is used.

Heap memory is used to store objects you create when your program executes.  It exists as long as your application is running.

Stack memory is used to store primitive data types and references (to things stored in the heap) when your program executes.  It is thread specific.

Blocks of memory are added and removed from the stack as your program executes.  They are created in a LIFO (last in first out) fashion when a method is invoked.  They are released when the method has finished execution.

I'm a novice Java developer and just getting my feet wet with memory management.  Can someone explain heap vs stack and how these work?

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What is event driven architecture?

What is event driven architecture?

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BeanPostProcessor Example | Spring Boot

What does SpringApplication.run() do?

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How do you create an index in MongoDB?

What is DefaultKafkaConsumerFactory?

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Is there a Log4j2 vulnerability with Spring Boot?

The JIT Compiler in Java

Java Heap vs Stack?

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Software Engineer Salary?

FewerLinesThanYou

What is event driven architecture?

What is event driven architecture?

Spring Boot Kafka Consumer

BeanPostProcessor Example | Spring Boot

What does SpringApplication.run() do?

How does a unique index work in MongoDb?

How do you create an index in MongoDB?

What is DefaultKafkaConsumerFactory?

FileReader vs BufferedReader vs Scanner | Java

Is there a Log4j2 vulnerability with Spring Boot?

The JIT Compiler in Java

Java Heap vs Stack?

JavaScript Observables in 5 Minutes

What is the difference between heap and stack?

Software Engineer Salary?

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