Spring Boot Kafka Example

A demo project showcasing a Kafka-based messaging system using Spring Boot. It consists of two independent Spring Boot applications — a producer and a consumer — backed by a PostgreSQL database, with Kafka running in KRaft mode.

Project Structure

SpringBootKafka/
├── docker-compose.yaml          # Spins up Kafka, Kafdrop, PostgreSQL, and Adminer
├── kafka-example-producer/      # Spring Boot app exposing a REST API to publish Kafka messages
└── kafka-example-consumer/      # Spring Boot app that consumes Kafka messages and persists them

Tech Stack

• Java 25
• Spring Boot 4.1.0-SNAPSHOT
• Apache Kafka 3.9.2 (KRaft mode — no Zookeeper)
• PostgreSQL (via Spring Data JPA)
• Gradle (build tool)
• Docker Compose (local infrastructure)

Services (Docker Compose)

Service	Description	Port
Kafka	Message broker (KRaft mode)	9092
Kafdrop	Kafka web UI	9000
PostgreSQL	Relational database	5432
Adminer	Database web UI	8080

Getting Started

Prerequisites

• Docker & Docker Compose
• Java 25+

1. Start the infrastructure

docker compose up -d

2. Run the Producer

cd kafka-example-producer
./gradlew bootRun

3. Run the Consumer

cd kafka-example-consumer
./gradlew bootRun

Modules

kafka-example-producer

A Spring Boot web application that exposes REST endpoints to publish messages to a Kafka topic. It also persists data to PostgreSQL via Spring Data JPA.

Key dependencies: spring-boot-starter-web, spring-boot-starter-kafka, spring-boot-starter-data-jpa, postgresql

kafka-example-consumer

A Spring Boot application that listens to a Kafka topic and processes incoming messages. It persists consumed data to PostgreSQL via Spring Data JPA.

Key dependencies: spring-boot-starter-kafka, spring-boot-starter-data-jpa, postgresql

Running Tests

From either module directory:

./gradlew test