Crypto Wallet Service

A cryptocurrency wallet management service built with Java 21, Spring Boot 3, and hexagonal architecture. Manage crypto wallets, track assets, and simulate profit/loss scenarios.

Features

• Create wallets
• Add crypto assets (BTC, ETH, etc.) with real-time pricing
• Profit/loss simulation based on current market prices

Architecture

High Level Overview

🎯 What Each Layer Does

Application Layer (application/)

• Models: Business entities (User, Wallet, Asset) and value objects
• Ports: Interfaces defining what the app can do (in/) and what it needs (out/)
• Workflows: Use case orchestrators that coordinate domain services and external concerns
  • WalletWorkflow - Manages wallets and assets using WalletDomainService
  • ProfitSimulationWorkflow - Calculates profit/loss using ProfitCalculationService
• Services: Focused domain services used by workflows for specific business logic

Infrastructure Layer (infrastructure/)

• REST Controllers (adapter/in/rest/) - HTTP endpoints
• Database (adapter/out/postgres/) - Data persistence
• External APIs (adapter/out/coinmarketcap/) - Price data
• Config - Wiring everything together

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📁 Directory Structure

crypto-wallet-service/
├── service/                           # Main application module
│   └── src/
│       ├── main/java/com/crypto/wallet/
│       │   ├── application/           # 🎯 Business Logic Layer
│       │   │   ├── model/            # Domain entities
│       │   │   │   ├── primitives/   # Value objects (Email, WalletId, etc.)
│       │   │   │   ├── Asset.java
│       │   │   │   ├── User.java
│       │   │   │   └── Wallet.java
│       │   │   ├── port/             # Interfaces (Hexagonal Architecture)
│       │   │   │   ├── in/          # Incoming ports (Use Cases)
│       │   │   │   └── out/         # Outgoing ports (Use Cases)
│       │   │   ├── service/         # Domain services
│       │   │   ├── ProfitSimulationWorkflow.java  # Use case orchestrator for P&L calculations
│       │   │   └── WalletWorkflow.java            # Use case orchestrator for wallet operations
│       │   ├── infrastructure/       # 🔧 Technical Layer
│       │   │   ├── adapter/
│       │   │   │   ├── in/          # Incoming adapters
│       │   │   │   │   ├── rest/    # REST controllers & DTOs
│       │   │   │   │   └── cronjob/ # Scheduled tasks
│       │   │   │   └── out/         # Outgoing adapters
│       │   │   │       ├── postgres/    # Database implementations
│       │   │   │       └── coinmarketcap/   # External API clients
│       │   │   └── config/          # Configuration classes
│       │   └── CryptoWalletApplication.java
│       └── test/                     # Test suites
│           ├── integration/         # End-to-end tests
│           ├── architecture/        # Architecture validation tests
│           └── com/crypto/wallet/   # Unit tests mirroring main structure
├── webapp/                          # simple html and javascript web page 
├── deployment/                      # Docker & deployment configs
└── build.gradle                    # Build configuration

🧪 Testing

• architecture/ - Validates layer boundaries
• integration/ - Full end-to-end tests
• unit/ - Fast isolated business logic tests

Technology Stack

• Java 21
• Spring Boot 3
• PostgreSQL

Quick Start

Prerequisites

• Java 21+
• Docker (for PostgreSQL)

Backend Setup

# Clone repository
git clone <repository-url>
cd crypto-wallet-service

# Start PostgreSQL
./gradlew composeUp

# Start application 
COINCAP_API_KEY=${COINCAP_API_KEY} ./gradlew bootRun --args='--spring.profiles.active=dev'

# OR start main method directly with active dev profile
com.crypto.wallet.CryptoWalletApplication::main 

Frontend Setup

#navigate to webapp directory
cd webapp

# install dependencies
npm install
# start frontend development server
npm run dev

Shutdown

# Stop PostgreSQL
./gradlew composeDown

How to get COINCAP_API_KEY

• CoinCap API: https://docs.coincap.io
• Signup for Free to create the apiKey: https://pro.coincap.io/signup
• Assets: https://docs.coincap.io/#89deffa0-ab03-4e0a-8d92-637a857d2c91
• Price history: https://docs.coincap.io/#61e708a8-8876-4fb2-a418-86f12f308978