Microservice

Demo (Handle Kafka & Mongo)

About

this project uses SpringBoot 3 that helps creating production-grade and stand-alone java applications & services with absolute minimum fuss.

This project implements a Payment Service using hexagonal architecture. The service consumes messages from a Kafka topic, validates and stores them in a MongoDB database.

Architecture

The Payment Service follows the hexagonal (or ports/adapter) architecture:

• Core Domain: Contains the business logic and domain models.
• Ports: Define interfaces for incoming and outgoing interactions.
• Adapters: Implement the interfaces defined by the ports.

Payment Service Architecture

Project Structure

src/
    |-- common/
    |   |-- event/  
            └──PaymentEvent.java
    |   |-- exception/
    |
    |-- config/
    |   |-- kafka/
    |   |-- mongodb/
    |
    |-- core/
        |-- port/infra/
                └──PaymentDataGateway
        |-- domain/
        |   |-- model/
                └──Payment.java  
        |   |-- service/
                └──PaymentService.java    # interface
                └──PaymentServiceImpl.java
        |-- adapter/
            |-- messaging/
            |   |-- model/
            |   |   └──KPayment.java 
            |   └──KPaymentConsumer.java
            |-- mongodb/
            |   |-- model/ 
            |       └──MGPayment
            |   |-- respository
            |   └──PaymentAdapter.java
    |
    |-- Application.java
    |
    test/
|
docker-compose.yml
start-local-env.sh
pom.xml
README.md

Run Locally

Prerequisites

. Java environment

> java -version
java 22

. Have Maven Installed

> mvn -version
Apache Maven 3.9.8

Startup using CMD

mvn spring-boot:run

Development with docker

Make sure that you have installed the following tools on your local machine

1. Docker,
2. docker-compose. (you should have version 1.29 or higher)

Installing Docker Desktop (for Mac & Windows) is the easiest way to get your environment ready

Set up MongoDB cluster & Kafka Broker

A script that automates the process was provided ;)

./start-local-env.sh

After running the script

Once the script completes successfully:

MongoDB cluster will be available at mongodb://localhost:27017,localhost:27018,localhost:27019/test?replicaSet=rs0 Kafka broker will be accessible at localhost:9092

In order for your machine to recognize the hosts mongo1, mongo2, and mongo3, you must add these hostnames to your local hosts file as follows:

127.0.0.1       mongo1
127.0.0.1       mongo2
127.0.0.1       mongo3

The location of the hosts file varies by operating system:

• For macOS: /private/etc/hosts
• For Windows: C:/Windows/System32/drivers/etc/hosts

Note : We need to create a Mongo Replica Set in order to be able to test some promising features like @Transactional annotation, etc

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Access the MongoDB cluster

Compass is an interactive tool for querying, optimizing, and analyzing the MongoDB data

The Connection String URI Format For our Replica Set is as the following

mongodb://localhost:27017,localhost:27018,localhost:27019/?replicaSet=rs0

Visualize kafka cluster

Offset Explorer is one of the best kafka UI tool that allow to quickly view our kafka cluster, including the borkers, topics and consumers

1. Download & Install Offset Explorer
2. Launch the app & Add a New Connection
3. In the Advanced tab : Boostrap servers : localhost:9092

you can use Conduktor which is a beautiful and fully-featured desktop client for Apache Kafka

Testing

🚀 This project includes simple unit and integration tests to ensure the reliability and correctness of the payment service as it evolves

Unit Tests:

Example: PaymentServiceTest.java

tests individual components in isolation.

--

Integration Tests:

Example: PaymentTestIT.java

It tests the entire payment processing flow.

The integration test utilizes spring-kafka-test with an embedded Kafka broker and embedded MongoDB instance to simulate the production environment.

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Feel free to open an issue or submit a pull request if you have any suggestions or improvements!