🎓 Learnify Platform

Online Learning Platform — Microservices Architecture

A full-scale, cloud-native e-learning platform inspired by Udemy and Coursera, built with 12 Spring Boot 3.x microservices. Demonstrates distributed systems design, event-driven architecture, and modern DevOps practices.

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📌 Repository Description

Learnify is a microservices-based online learning platform built using Java 17, Spring Boot 3.2, and Spring Cloud. The system features 12 independent services communicating via OpenFeign (sync) and Apache Kafka (async), with full JWT authentication, Redis caching, Flyway migrations, Resilience4j circuit breakers, distributed tracing via Zipkin, and Docker Compose orchestration.

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📦 Microservices

#	Service	Port	Responsibility	Key Tech
1	API Gateway	8080	Single entry point, JWT filter, rate limiting, routing	Spring Cloud Gateway, Redis
2	Config Server	8888	Centralized configuration management	Spring Cloud Config
3	Service Registry	8761	Service discovery & registration	Netflix Eureka
4	Auth Service	8081	Login, signup, JWT issuance, refresh tokens, RBAC	Spring Security, JJWT
5	User Service	8082	User profiles, instructor management, Redis caching	JPA, Redis
6	Course Service	8083	Course CRUD, categories, publish workflow, caching	JPA, Redis, MapStruct
7	Lesson Service	8084	Sections, video/text lessons, ordering	JPA, Flyway
8	Enrollment Service	8085	Enroll students, track progress, Kafka consumer	Feign, Kafka, Resilience4j
9	Review Service	8086	Course ratings (1–5), reviews, average calculation	JPA
10	Payment Service	8087	Payment processing, Kafka event publisher	Kafka Producer
11	Notification Service	8090	Email notifications via Kafka consumers	Spring Mail, Kafka
12	Analytics Service	8091	Revenue tracking, enrollment stats, Kafka consumers	JPA, Kafka

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🛠 Tech Stack

Core	Java 17, Spring Boot 3.2, Maven (multi-module)
Service Mesh	Spring Cloud 2023 — Config, Eureka, Gateway, OpenFeign
Security	Spring Security 6, JWT (JJWT 0.12), RBAC (STUDENT / INSTRUCTOR / ADMIN)
Messaging	Apache Kafka 3.x (async events), OpenFeign (sync RPC)
Persistence	Spring Data JPA, Hibernate, PostgreSQL 15 (database-per-service)
Caching	Redis 7 — course catalog, user profiles (TTL: 30 min)
Resilience	Resilience4j — Circuit Breaker, Retry, Rate Limiter
Migrations	Flyway — versioned SQL migrations per service
Observability	Spring Actuator, Micrometer, Zipkin distributed tracing
Docs	SpringDoc OpenAPI 3 / Swagger UI — per service + gateway aggregation
Code Gen	Lombok (boilerplate), MapStruct (compile-time DTO mapping)
Testing	JUnit 5, Mockito, Testcontainers
DevOps	Docker, Docker Compose (20+ containers)

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🗃 Database Design

Each service owns its own PostgreSQL schema (database-per-service pattern):

 auth_db
 └── users            (id, email, password, role, is_active)
 └── refresh_tokens   (id, token, user_id, expires_at, is_revoked)

 user_db
 └── user_profiles    (id, email, first_name, bio, headline, role)

 course_db
 └── categories       (id, name, slug, parent_id)
 └── courses          (id, title, instructor_id, category_id, price, status, avg_rating)

 lesson_db
 └── sections         (id, course_id, title, order_index)
 └── lessons          (id, section_id, title, type, video_url, order_index)

 enrollment_db
 └── enrollments      (id, student_id, course_id, status, progress_pct) UNIQUE(student,course)

 review_db
 └── reviews          (id, student_id, course_id, rating 1-5, comment) UNIQUE(student,course)

 payment_db
 └── payments         (id, student_id, course_id, amount, status, transaction_id)

 analytics_db
 └── course_analytics (course_id, total_enrollments, total_revenue, completion_rate)

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🌐 Service URLs

Portal	URL
🔀 API Gateway	http://localhost:8080
🗂 Eureka Dashboard	http://localhost:8761
📋 Swagger — Auth	http://localhost:8081/swagger-ui.html
📋 Swagger — Courses	http://localhost:8083/swagger-ui.html
📋 Swagger — Enrollment	http://localhost:8085/swagger-ui.html
📊 Kafka UI	http://localhost:8092
🔍 Zipkin Tracing	http://localhost:9411

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🔐 Authentication & Authorization

Roles

Role	Permissions
STUDENT	Browse courses, enroll, review, track progress
INSTRUCTOR	Create & publish courses, manage lessons, view analytics
ADMIN	Full platform access

Auth Flow

# 1. Register
curl -X POST http://localhost:8080/api/auth/register \
  -H "Content-Type: application/json" \
  -d '{
    "firstName": "Jane",
    "lastName": "Doe",
    "email": "jane@example.com",
    "password": "Secure@1234",
    "role": "STUDENT"
  }'

# 2. Login → receive JWT
curl -X POST http://localhost:8080/api/auth/login \
  -H "Content-Type: application/json" \
  -d '{"email":"jane@example.com","password":"Secure@1234"}'

# 3. Use JWT in subsequent requests
curl http://localhost:8080/api/courses \
  -H "Authorization: Bearer <your_jwt_token>"

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📖 API Documentation

Core Endpoints

Courses

GET    /api/courses              → Search & filter published courses
GET    /api/courses/{id}         → Get course details (cached in Redis)
POST   /api/courses              → Create course [INSTRUCTOR]
PUT    /api/courses/{id}         → Update course [INSTRUCTOR]
PATCH  /api/courses/{id}/publish → Publish course [INSTRUCTOR]
GET    /api/courses/popular      → Top courses by enrollment

Enrollment

POST  /api/enrollments           → Enroll in a course (via Feign → Course Service)
GET   /api/enrollments/my        → My enrolled courses
PATCH /api/enrollments/{courseId}/progress → Update lesson progress

Payments

POST /api/payments               → Process payment (publishes Kafka event)
GET  /api/payments/my            → My payment history
GET  /api/payments/{id}          → Payment details

Reviews

POST /api/reviews                → Submit course review (1–5 stars)
GET  /api/reviews/course/{id}    → Course reviews (paginated)
GET  /api/reviews/course/{id}/rating → Average rating
PUT  /api/reviews/{id}           → Update review

Analytics (INSTRUCTOR/ADMIN)

GET /api/analytics/courses/{courseId}   → Course stats & revenue
GET /api/analytics/courses/top-revenue  → Top earning courses

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🧪 Testing

# Run all unit tests
mvn test

# Run tests for specific service
cd auth-service && mvn test
cd enrollment-service && mvn test
cd payment-service && mvn test
cd course-service && mvn test

# Run with coverage report
mvn test jacoco:report

Test coverage includes:

• ✅ AuthServiceTest — register, login, duplicate email, invalid credentials
• ✅ CourseServiceTest — create, fetch, not-found, publish flow
• ✅ EnrollmentServiceTest — enroll, duplicate check, progress update, completion
• ✅ PaymentServiceTest — process payment, duplicate payment rejection, Kafka publish

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🏛 Architecture Patterns

Pattern	Implementation
Database per Service	Each service has its own PostgreSQL instance
API Gateway	Single entry point — auth, routing, rate limiting
Event-Driven (Saga)	Payment → Enrollment choreography via Kafka
Circuit Breaker	Resilience4j on all Feign clients
CQRS (lite)	Redis cache for hot read paths
DTO Pattern	Request/Response DTOs, never expose entities
Repository Pattern	Spring Data JPA repositories
Compile-time Mapping	MapStruct — zero reflection DTO mapping

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🔭 Observability

# Health check any service
curl http://localhost:808X/actuator/health

# View distributed traces
open http://localhost:9411     # Zipkin UI

# Monitor Kafka topics & consumers
open http://localhost:8092     # Kafka UI

# Metrics (Prometheus-compatible)
curl http://localhost:808X/actuator/metrics
curl http://localhost:808X/actuator/prometheus

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🤝 Contributing

1. Fork the repository
2. Create your branch: git checkout -b feature/your-feature
3. Commit your changes: git commit -m 'feat: add your feature'
4. Push to the branch: git push origin feature/your-feature
5. Open a Pull Request