Notification System

A full-stack notification platform built with Spring Boot and React.
It supports sending notifications over multiple channels, tracks delivery state, and includes an admin console for operations like retries, templates, user preferences, and runtime health/metrics.

What this project includes

• Notification API to create and track notifications
• Multi-channel delivery support (EMAIL, SMS, PUSH)
• Kafka-based async processing with retry + DLQ flow
• Idempotency support on send requests (Idempotency-Key header)
• Per-user/channel preference management
• Admin APIs for notification listing and manual retry
• Template management APIs (upsert/list/get by channel)
• Redis-based caching and rate limiting
• Actuator health/info/metrics exposure
• React admin dashboard with tabs for:
  • Notifications
  • Templates
  • Preferences
  • Actuator
  • Metrics

Tech stack

Backend:

• Java 21
• Spring Boot 4
• Spring Web MVC, Validation, JPA
• Kafka
• Redis
• MySQL
• Spring Actuator

Frontend:

• React + Vite
• Tailwind CSS

API overview

Base URL: http://localhost:8080

• POST /notifications -> create notification (accepts optional Idempotency-Key)
• GET /notifications/{notificationId} -> get current status
• GET /admin/notifications?status=... -> list notifications for admin
• POST /admin/notifications/{notificationId}/retry -> trigger manual retry
• PUT /admin/templates -> create/update template
• GET /admin/templates -> list templates
• GET /admin/templates/{templateId}?channel=... -> fetch specific template
• PUT /preferences/{userId} -> create/update user preferences
• GET /preferences/{userId} -> get user preferences
• GET /actuator/health
• GET /actuator/info
• GET /actuator/metrics

Local setup

1) Start infrastructure

Make sure these are running locally:

• MySQL on 3306
• Kafka on 9092
• Redis on 6379

Default values are already configured in src/main/resources/application.properties, but can be overridden using environment variables.

2) Run backend

./mvnw spring-boot:run

Backend starts on http://localhost:8080.

3) Run frontend

cd webapp
npm install
npm run dev

Frontend starts on http://localhost:5173.