🛒 E-Commerce REST API (Spring Boot)

This is the backend for the E-Commerce, designed to handle secure data persistence, user authentication, and product management. It serves as the RESTful API for the Flutter Mobile Client.

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🛠️ Tech Stack & Architecture

• Language: Java 25
• Framework: Spring Boot 4.0.5 (Spring Web, Spring Data JPA)
• Security: Spring Security 6 with JWT (JSON Web Tokens)
• Database: Microsoft SQL Server
• Build Tool: Maven

Layered Architecture

The project follows a strict separation of concerns to ensure scalability and maintainability:

1. Controller Layer: REST Endpoints and Request Mapping.
2. Service Layer: Business logic, password encoding, and JWT generation.
3. Repository Layer: Data persistence using Spring Data JPA.
4. Security Layer: Custom JWT Filters and Role-Based Access Control (RBAC).

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✨ Key Technical Implementations

🔒 Security & Authentication

• JWT Stateless Auth: Custom JwtAuthenticationFilter that intercepts requests to validate Bearer tokens.
• Role-Based Access (RBAC): Configured SecurityConfig to restrict product/category management to ADMIN users while allowing USER access for browsing.
• Global Exception Handling: Implemented @RestControllerAdvice to provide clean, consistent JSON error responses for database conflicts (e.g., duplicate usernames) and runtime errors.

📁 Media & Resource Handling

• Multi-Part File Support: Handles image uploads for products using MultipartFile.
• Static Resource Mapping: A custom WebMvcConfigurer maps internal storage folders (user-photos/) to public URLs (/uploads/**) for consumption by the Flutter app.

💾 Database Design

The system manages relationships between Users, Products, and Categories with a focus on data integrity:

• Many-to-One Relationships: Products are linked to Categories.
• Transactional Integrity: Uses @Transactional to safely handle category deletions while preserving linked product data.

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🚀 API Endpoints (Samples)

Method	Endpoint	Access	Description
POST	/api/auth/register	Public	Register new user (Default: ROLE_USER)
POST	/api/auth/login	Public	Authenticate and receive JWT
GET	/api/products	Public	View all products
POST	/api/products	Admin	Add new product with image upload
DELETE	/api/categories/{id}	Admin	Safely remove category (cascades to products)

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⚙️ How to Run

1. Clone the repo:

   git clone [https://github.com/Doeun-Panha/e-commerce-spring.git](https://github.com/Doeun-Panha/e-commerce-spring.git)