Wallet Service Coding Challenge 💰

This is a Java 17 Spring Boot 3 project implemented using hexagonal architecture that includes features such as records, streams API, Specifications, Paginable, JpaRepository, ControllerAdvice, RestControllers, and enums among others. All whilst adhering to Google's Java Style Guide you too can get a format spec for your favourite IDE here 😁

Technologies Used

• Docker 🐳
• Java 17 ☕️
• Spring Boot 3 🍃
• PostgreSQL 🐘
• Mockito 5 & JUnit 5 🧪

Architecture

This project follows a hexagonal architecture pattern, with ports and adapters. JpaRepositories create their adapter at runtime so there's no need for the output adapter folder. Communication between different components is done through interfaces and DTOs

Running the Application with Docker Compose

To run the application using Docker Compose, follow these steps:

1. Clone the repository to your local machine
2. Navigate to the project directory
3. Run the following command to start the application and its database docker-compose up
4. The application should now be running on http://localhost:8001
5. PostgreSQL should be running on port 5432 with user postgres, password postgres and database called wallet_service_db
6. Starter data is automatically seeded and reset with each run
7. Should you run into any issues, it can be built with maven and it runs on the same ports locally, you'd just have to ensure that the wallet_service_db exists before running it so that hibernate can populate it

Dockerized Components

The entire application (Spring App & PostgreSQL) is dockerized, the maven build process also happens within the container to ensure portability.

Solution considerations and implementations

• This project provides an implementation of Wallet, BankAccounts, Transactions and Payments the implementation is served through 4 REST API endpoints:

  • Check wallet balance
  • Set bank account details to transfer funds to and from
  • Create wallet transactions
  • Retrieve wallet transaction history

• Every User has a Wallet

• All Wallets are linked to OnTop's BankAccount

• Wallet and BankAccount funds are checked before each withdraw

• Creating a WalletTransaction triggers an interaction with the Payment provider, this interaction generates both a WalletTransaction and PaymentTransaction and moves the funds

• All fund transfers happen from BankAccount to BankAccount i.e. your Wallet (OnTop's BankAccount & your other BankAccount)

• A 10% fee is applied to all Wallet withdrawals and credited to the OnTop Bank Account. i.e if transferring $1000.00 the destination BankAccount receives $900.00 with the remaining $100.00 going to the OnTop BankAccount

• Wallet balances are synchronized to reflect PaymentTransactions and status

• Refunds are honored on failed withdrawals and a new transaction is created to move the money back

  • Some exceptions like throwing 500 and 404 on matching user_id were thrown for fun since they were included in the mocks 😁

Process flow

A Postman collection with examples is included inside the resources folder. You can access the folder here.

• You are provided with user_ids 1 & 2 starting with $10000.00 and $5000.00 respectively in their wallets
• You can check your funds with your user_id at any time by visiting localhost:8001/wallets/balance?user_id=1
• Use the endpoint localhost:8001/wallets/transactions/bank to set your bank account details
• Once the banking details are set you are free to move money to and from your user's wallet localhost:8001/wallets/transactions until you run out of funds, just click away until your run out of funds, then transfer some more and keep going.
• You can also view your transaction history at any point through localhost:8001/wallets/transactions/history this api provides granularity by providing date range and amount range filters. Results are ordered in descending order and the amount of results per page as well as the page can be adjusted through the request.
• Fun-fact all dummy data in the database are a reference to The Little Prince 👑🦊🌹