Simdex – SIMulated DEXchange (Spring Boot Backend)

Simdex is a simulation platform for decentralized crypto exchange logic, built with Spring Boot. It features secure user registration/login, crypto price tracking via CoinMarketCap, and basic portfolio management. Designed as an educational and prototyping project for fullstack blockchain enthusiasts.

🧪 This backend powers the Simdex Frontend

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💡 Key Features

• ✅ User Registration & Login with Spring Security
• 🔑 JWT Authentication with token-based sessions
• 📈 Live Crypto Price Tracking using CoinMarketCap API
• 💼 User Portfolio Structure for holding simulated assets
• 📦 Modular architecture with clean domain separation
• 🧪 Ready for REST API testing (Postman/Insomnia)

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🔐 Auth System

• /auth/register → creates a new user
• /auth/login → returns JWT token
• Role system via ERole.ROLE_ADMIN, extendable

Spring Security is fully configured with:

• AuthenticationManager
• BCrypt password encoding
• TokenService for JWT generation

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📊 Crypto Price Endpoint

• /api/v2/price → Returns real-time BTC price from CoinMarketCap API
• Uses native Java 11+ HttpClient and javax.json to parse the response
• Requires a valid API key from CMC in the controller

JsonObject cryptoData = jsonObject.getJsonObject("data").getJsonObject("BTC");
JsonNumber price = cryptoData.getJsonObject("quote").getJsonObject("USD").getJsonNumber("price");

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📂 Project Structure

/controllers
    AuthController.java          → login/register endpoints
    CMCIntegrationController.java → price data from CoinMarketCap
    SimdexController.java        → basic health/test routes

/domain
    user/                        → user, roles, DTOs
    crypto/                      → (holdings, portfolio – WIP)

/repositories
    UserRepository.java

/security
    SecurityConfig.java
    TokenService.java

/resources
    application.properties

pom.xml

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▶️ How to Run

Prerequisites

• Java 17+
• Maven
• PostgreSQL (or H2 for dev)
• CoinMarketCap API Key (free plan works)

Steps

git clone https://github.com/sbrunomello/simdex.git
cd simdex
mvn spring-boot:run

Backend will run on:
http://localhost:8080

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🧪 Example Requests

Register

POST /auth/register
{
  "username": "mello",
  "password": "123456",
  "email": "mello@example.com",
  "firstName": "Bruno",
  "lastName": "Mello"
}

Get BTC Price

GET /api/v2/price
→ name: Bitcoin | price: 69234.56

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🧩 Frontend

Simdex is designed to work with:
👉 simdex-web – Angular app for user interface, wallet, and order management

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🚀 Roadmap

• Add real-time price updates via WebSocket
• User portfolio API (add/remove simulated assets)
• Simulated buy/sell logic
• Historical chart tracking (via CMC)
• Admin dashboard

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📬 Contact

• GitHub
  Built with ⚙️ by Mello