A robust, scalable notification service built with Spring Boot, designed to handle multi-channel notifications including Email, SMS (via Twilio), and Push Notifications (via Firebase). This service uses an event-driven architecture with RabbitMQ to ensure high availability and reliability.

• Multi-channel Support: Send notifications via Email, SMS, and Push.
• Event-Driven Architecture: Decoupled notification processing using RabbitMQ.
• Persistence: Stores notification history and status in MongoDB.
• Scalable: Dockerized and ready for deployment.
• RESTful API: Simple endpoints to trigger and retrieve notifications.

• Core: Java 17, Spring Boot 4+
• Database: MongoDB
• Message Broker: RabbitMQ
• Integrations:
  • Email: Java Mail Sender (SMTP)
  • SMS: Twilio
  • Push: Firebase Cloud Messaging (FCM)
• Containerization: Docker, Docker Compose
• Tools: Lombok, Maven

Before running the application, ensure you have the following installed:

• Java 17+
• Docker & Docker Compose
• Maven (optional, included via wrapper)

The application relies on environment variables for sensitive configuration. You can set them in a .env file in the root directory.

Create a .env file in the project root with the following structure:

# Server
SERVER_PORT=8080

# MongoDB
MONGODB_HOST=mongodb
MONGODB_PORT=27017
MONGODB_DATABASE=notification_db
MONGO_INITDB_ROOT_USERNAME=root
MONGO_INITDB_ROOT_PASSWORD=password

# RabbitMQ
RABBITMQ_HOST=rabbitmq
RABBITMQ_PORT=5672
RABBITMQ_DEFAULT_USER=guest
RABBITMQ_DEFAULT_PASS=guest

# Email (Gmail SMTP example)
MAIL_USERNAME=your_email@gmail.com
MAIL_PASSWORD=your_app_password

# Twilio (SMS)
TWILIO_ACCOUNT_SID=your_twilio_sid
TWILIO_AUTH_TOKEN=your_twilio_auth_token
TWILIO_FROM_NUMBER=your_twilio_number

# Firebase (Push)
FIREBASE_CONFIG_PATH=classpath:firebase/firebase-service-account.json

This requires no manual local setup of MongoDB or RabbitMQ.

1. Build and Run:

   docker-compose up -d --build

2. The application will be available at http://localhost:8080.
3. To stop:

   docker-compose down

1. Start Infrastructure: Ensure you have MongoDB and RabbitMQ running locally or use Docker for just the infra:

   docker-compose up -d mongodb rabbitmq

2. Run Application:

   ./mvnw spring-boot:run

POST /api/v1/notifications/send

{
  "recipient": "+1234567890",
  "subject": "Welcome!",
  "content": "Thanks for signing up.",
  "type": "SMS" 
}

Types: SMS, EMAIL, PUSH

GET /api/v1/notifications

GET /api/v1/notifications/{id}

1. Client sends a POST request to /api/v1/notifications/send.
2. Controller receives the request and validates it.
3. Service saves the notification with status PENDING to MongoDB.
4. Producer sends the Notification ID to RabbitMQ.
5. Consumer listens to the queue, picks up the ID, and retrieves full details from MongoDB.
6. Channel Resolver determines the correct channel (SMS, Email, Push) and dispatches the message via the corresponding 3rd party API.
7. Service updates the notification status to SENT or FAILED in MongoDB.