Spring Boot Kafka Service Documentation

Overview

This document outlines the setup and configuration for a Spring Boot application that utilizes Apache Kafka for messaging. The application is built with Maven and Java 17, and it also integrates a MySQL database. Apache Kafka, Zookeeper, and Kafdrop are containerized using Docker Compose.

Project Structure

The project is structured following standard Maven conventions:

• src/main/java/com/kafka/service: Contains the main application codebase.
  • application: Contains command handlers and DTOs.
  • domain: Contains the domain services.
  • infrastructure: Contains adapters for web, messaging (Kafka), and configuration classes.
• src/main/resources: Contains configuration files and resources.
• src/test/java: Contains unit and integration tests.

Configuration Files

• application.properties or application.yml: Defines Spring Boot specific configurations including server port, database settings, and Kafka properties.
• docker-compose.yml: Defines the services for Kafka, Zookeeper, and Kafdrop, along with their respective configurations.

Kafka Configuration

The Kafka configuration is managed within the KafkaConfiguration class:

• producerFactory: Defines the configuration properties for Kafka producers.
• kafkaTemplate: Provides a template for sending messages to Kafka topics.
• consumerFactory: Defines the configuration properties for Kafka consumers.
• kafkaListenerContainerFactory: Sets up the listener container for Kafka messages.

Default Kafka Settings

• Group ID: example
• Topic: pdf
• Kafka Broker: localhost:29092

Changing Configuration Parameters

To modify Kafka settings, update the producerFactory and consumerFactory methods in the KafkaConfiguration class with the desired properties.

Docker Compose for Kafka

The docker-compose.yml file sets up the Kafka environment:

• zookeeper: Manages Kafka's state.
• kafka: The Kafka broker itself.
• kafdrop: A web UI for viewing Kafka topics and browsing consumer groups.

Volumes

• kafka_data: Stores Kafka's data persistently.

Ports

• Zookeeper: 2181
• Kafka: 9092 for internal and 29092 for external connections.
• Kafdrop: 9010

Running the Project

• The Spring Boot application runs on port 8090.
• Kafka and its components are started with Docker Compose using the docker-compose.yml file.

Sending Messages

To send messages to Kafka, use the sendMessage endpoint defined in the MessageController:

• HTTP POST to /api/messages/send
• Request body should contain the SendKafkaMessageCommand JSON structure.

Consuming Messages

Kafka messages are consumed by the KafkaListener methods within the application, which process incoming messages from the configured topics.

Additional Notes

• The project is not fully containerized; only the Kafka setup is managed with Docker Compose.
• To view Kafka topics and message flows, access Kafdrop at http://localhost:9010.

Conclusion

This documentation provides a basic outline for the Spring Boot Kafka Service project. For detailed configuration and usage, refer to the source code and configuration files.