Digital Wallet

Backend Architecture Diagram

graph LR
    Client["👤 Frontend / API Client"] -->|"HTTP + JWT"| Security["🛡️ Spring Security\nSecurityConfig + JwtAuthFilter"]

    Security -->|"/auth/**"| AuthController["🔐 AuthController"]
    Security -->|"/wallets/**"| WalletController["💳 WalletController"]
    Security -->|"/me"| IdentityController["🙋 IdentityController"]
    Security -->|"/health"| HealthController["🩺 HealthController"]

    AuthController --> AuthService["AuthService"]
    AuthService --> UserRepo["UserRepository"]
    AuthService --> JwtService["JwtService"]
    AuthService --> PasswordEncoder["BCryptPasswordEncoder"]

    IdentityController -->|"userId from Authentication"| JwtAuthFilter["JwtAuthFilter"]

    WalletController --> WalletService["WalletService"]
    WalletService --> WalletRepo["WalletRepository"]
    WalletService --> TxRepo["WalletTransactionRepository"]
    WalletService --> UserRepo
    WalletService --> RiskService["RiskService"]

    RiskService --> RiskRules["RiskRule implementations\n• LargeAmount\n• HighVelocityWithdrawal\n• TransferRisk"]
    RiskService --> RiskRepo["RiskEventRepository"]

    UserRepo --> Postgres[("🐘 PostgreSQL")]
    WalletRepo --> Postgres
    TxRepo --> Postgres
    RiskRepo --> Postgres

    Flyway["🛠️ Flyway Migrations\nV1/V2/V3 SQL"] --> Postgres

    style Security fill:#052e16,stroke:#4ade80,color:#bbf7d0
    style WalletService fill:#451a03,stroke:#f59e0b,color:#fef3c7
    style RiskService fill:#1e1b4b,stroke:#818cf8,color:#c7d2fe
    style Postgres fill:#172554,stroke:#3b82f6,color:#bfdbfe

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Quick Start

1) Start PostgreSQL

docker compose up -d db

2) Start backend

cd backend
mvn spring-boot:run
# if 8080 is busy:
# mvn spring-boot:run -Dspring-boot.run.arguments="--server.port=8081"

Backend API: http://localhost:8080

3) Start frontend demo

In a new terminal from repo root:

python3 -m http.server 4173 -d frontend

Open http://localhost:4173

Troubleshooting

• If cd /workspace/Digital-Wallet fails on your local machine, use your actual local path to this repository.
• If python command is missing, use python3.
• If Maven cannot download dependencies, verify network/proxy and Maven Central access.
• If you run backend on another port (e.g. 8081), set the frontend API Base URL in the UI before login.
• If you open http://localhost:4173/auth/login or /auth/register in browser, that hits the static frontend server. Use frontend UI or call backend API base URL for auth endpoints.

Backend flow at a glance

• Auth path: POST /auth/register and POST /auth/login are public, handled by AuthController + AuthService, and issue JWTs via JwtService.
• Protected path: all wallet operations (create/list/deposit/withdraw/transfer/history) require JWT, are handled by WalletController, and execute transactional logic in WalletService.
• Risk scoring: each money movement is assessed by RiskService using pluggable RiskRule components and persisted as risk_events.
• Persistence: all repositories store domain data in PostgreSQL, with schema managed by Flyway migrations.