E-Commerce Lite - Spring Boot Backend

📋 Project Overview

E-Commerce Lite is a simplified online store backend API built with Spring Boot. It provides core e-commerce functionality including user management, product catalog, and order processing with inventory management.

🎯 Core Features

• User Management: Create and manage customer profiles
• Product Catalog: Full CRUD operations for products with inventory tracking
• Order System: Process orders with automatic stock validation and total calculation
• Inventory Management: Real-time stock updates with business logic enforcement
• RESTful API: Clean JSON API for frontend clients

🏗️ System Architecture

Database Schema

users (id, email, name, created_date)
products (id, name, description, price, stock_quantity, created_date)
orders (id, user_id, total_amount, status, created_date)
order_items (id, order_id, product_id, quantity, price)

Key Business Rules

• Orders automatically calculate totals based on product prices
• Stock quantities are validated before order processing
• Inventory is updated in real-time upon successful orders
• Orders cannot exceed available stock quantities

📁 Final Project Structure

src/main/java/com/ecommerce/ecommercelite/
├── config/
│   └── SwaggerConfig.java              # API documentation
├── controller/
│   ├── UserController.java             # User management endpoints
│   ├── ProductController.java          # Product catalog endpoints
│   └── OrderController.java            # Order processing endpoints
├── dto/
│   ├── OrderRequest.java               # Order creation payload
│   ├── OrderResponse.java              # Order response format
│   ├── ProductRequest.java             # Product creation/update payload
│   └── UserRequest.java                # User creation payload
├── entity/
│   ├── User.java                       # User entity with orders relationship
│   ├── Product.java                    # Product entity with inventory
│   ├── Order.java                      # Order entity with total calculation
│   └── OrderItem.java                  # Order-item join entity
├── repository/
│   ├── UserRepository.java             # User data access
│   ├── ProductRepository.java          # Product data access
│   └── OrderRepository.java            # Order data access
├── service/
│   ├── UserService.java                # User business logic
│   ├── ProductService.java             # Product business logic
│   └── OrderService.java               # Order processing logic
└── EcommerceLiteApplication.java       # Main application class

src/main/resources/
├── application.properties              # Database & server configuration
└── data.sql                            # Optional sample data

src/test/java/com/ecommerce/ecommercelite/
├── service/
│   ├── UserServiceTest.java
│   ├── ProductServiceTest.java
│   └── OrderServiceTest.java
└── controller/
    ├── UserControllerTest.java
    ├── ProductControllerTest.java
    └── OrderControllerTest.java

🔧 Technical Implementation

Technology Stack

• Framework: Spring Boot 3.2.x
• Database: MySQL with Spring Data JPA
• Build Tool: Maven
• Java Version: 17+
• Validation: Bean Validation API
• Documentation: SpringDoc OpenAPI

Key Spring Boot Features Used

• Spring Data JPA for database operations
• Spring MVC for REST controllers
• Transaction management for data consistency
• Bean validation for input sanitization
• Repository pattern for data access abstraction

🚀 API Endpoints

Users

• GET /api/users - List all users
• GET /api/users/{id} - Get user by ID
• POST /api/users - Create new user
• GET /api/users/{id}/orders - Get user's order history

Products

• GET /api/products - List all products (with pagination)
• GET /api/products/{id} - Get product details
• POST /api/products - Create new product (admin)
• PUT /api/products/{id} - Update product (admin)
• DELETE /api/products/{id} - Delete product (admin)

Orders

• GET /api/orders - List all orders
• GET /api/orders/{id} - Get order details
• POST /api/orders - Create new order
• PUT /api/orders/{id}/cancel - Cancel order

💡 How It Works

Order Processing Flow

1. Request Validation: Validate order items and quantities
2. Stock Check: Verify sufficient inventory for all items
3. Price Calculation: Calculate order total using current product prices
4. Inventory Update: Reduce stock quantities atomically
5. Order Creation: Save order with items in single transaction
6. Response: Return order confirmation with details

Database Relationships

• One-to-Many: User → Orders
• One-to-Many: Order → OrderItems
• Many-to-One: OrderItem → Product
• Bi-directional: Orders can navigate to User and Products

Business Logic Layer

• Service classes encapsulate complex business rules
• Transactional boundaries ensure data consistency
• Custom exceptions for business rule violations
• Automatic total calculations and inventory management

🛠️ Setup & Development

Prerequisites

• Java 17+
• MySQL 8.0+
• Maven 3.6+

Configuration

# Database
spring.datasource.url=jdbc:mysql://localhost:3306/ecommerce_db
spring.datasource.username=username
spring.datasource.password=password

# JPA
spring.jpa.hibernate.ddl-auto=update
spring.jpa.show-sql=true

Running the Application

mvn spring-boot:run

🧪 Testing Strategy

• Unit tests for service layer business logic
• Integration tests for repository layer
• MockMvc tests for controller endpoints
• Test data builders for easy test creation
• Transaction rollback for test isolation

📈 Learning Outcomes

By building this project, you'll master:

• Spring Boot application structure and best practices
• JPA entity relationships and mapping
• REST API design and implementation
• Transaction management and data consistency
• Business logic layer development
• Testing strategies for Spring applications
• Database design for real-world scenarios

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Ready to start coding? This structure will give us a professional-grade Spring Boot application that demonstrates real e-commerce functionality while following industry best practices.