Expense Tracker API

A production-grade Backend API for tracking personal expenses, built with Spring Boot and MySQL. This project is designed to simulate a real-world financial application with secure authentication, complex queries, and external integrations.

🚀 Features

• User Management: Secure Sign Up & Login with JWT Authentication.
• Expense Tracking: CRUD operations for expenses (Title, Amount, Category, Date) with Pagination & Sorting.
• Advanced Analytics: Monthly spending breakdown by category.
• Security: Role-based access (RBAC), Rate Limiting (10 req/min), and Stateless Session.
• Integrations:
  • File Upload: Attach receipts to expenses.
  • Email Notification: (Mock) Welcome emails on registration.
  • Currency Exchange: Real-time USD exchange rates via external API.
• Performance: Caching support for expense retrieval.

🛠️ Tech Stack

• Language: Java 11
• Framework: Spring Boot 2.7.x
• Database: MySQL 8.0
• Security: Spring Security & JJWT
• Documentation: Swagger UI / OpenAPI 3.0

⚙️ Prerequisites

• Java 11 SDK installed.
• Maven installed.
• MySQL Server running on localhost:3306.

📦 Setup & Installation

1. Database Setup

Create a database named expense_tracker in MySQL:

CREATE DATABASE expense_tracker;

2. Configure Credentials

This project uses Environmental Variables for security (Zero hardcoded secrets). You must pass these values when running the application.

• DB_USERNAME: Your MySQL username (e.g., root)
• DB_PASSWORD: Your MySQL password.
• JWT_SECRET: A secure random string (min 32 chars).

▶️ How to Run

Using Maven (Command Line)

Open your terminal in the project root and run:

mvn spring-boot:run "-Dspring-boot.run.arguments=--DB_USERNAME=root --DB_PASSWORD=your_password --JWT_SECRET=your_secret_key"

Using IntelliJ IDEA / Eclipse

1. Open Run/Debug Configurations.
2. Add the following to Environment Variables:
   • DB_USERNAME=root
   • DB_PASSWORD=your_password
   • JWT_SECRET=your_secret_key
3. Click Run.

📖 API Documentation

Once the server is running, access the interactive Swagger UI to test all endpoints: http://localhost:8080/swagger-ui/index.html

Authentication:

1. Use POST /api/auth/signin to get a token.
2. Click the Authorize button (top right).
3. Enter Bearer <your_token>.

📂 Project Structure

src/main/java/com/expensetracker/
├── config/        # Security, Swagger, CORS, RateLimiting
├── controller/    # REST API Endpoints
├── dto/           # Data Transfer Objects
├── model/         # JPA Entities
├── repository/    # Database Access Layer
├── service/       # Business Logic & External Integrations
├── exception/     # Global Error Handling
└── util/          # Helper classes (JWT)