Money Transfer API

This is a simple REST API that allows users to create and manage accounts, and transfer money between them. The API is built using Java 17 and Spring Boot 3.0.4, and uses a PostgreSQL database to store account information and transaction history. It is designed to be stateless and uses JWT for authentication and authorization.

Features

The API includes the following endpoints:

POST /api/v1/accounts: Creates a new account with a starting balance.

GET /api/v1/accounts/{id}: Retrieves the account information.

POST /api/v1/transfers: Transfers money from one account to another.

POST /api/v1/auth/register: Generates a JWT access token for a user.

POST /api/v1/auth/authenticate: Authenticates user and responds with a JWT access token.

The API enforces the following constraints:

• An account cannot have a negative balance.
• The transfer amount must be greater than zero.
• If the source account does not have enough funds, the transfer will fail.
• The API is designed to handle concurrent requests and avoid race conditions.

Getting Started

To build and run the API locally, you'll need the following dependencies:

Java 17

PostgreSQL

Docker (optional)

Database Setup

Before running the API, you'll need to create a new PostgreSQL database:

CREATE DATABASE bank-api;

Running the API

To run the API, you can either run it directly from your IDE or build a Docker image and run it inside a container.

Running from IDE

Clone the repository.

Open the project in your favorite IDE.

Rename application.properties.example to application.properties.

Configure the database connection in application.properties to match yor db and db credentials.

Run the MoneyTransferApplication class.

Running with Docker

Clone the repository.

Build the Docker image:

mvn install

docker build -t money-transfer-0.0.1.jar .

Run the Docker container:

docker run -p 8080:8080 money-transfer-0.0.1.jar

Authentication and Authorization

The API is stateless and uses JWT for authentication and authorization. To authenticate, clients must send a POST request to /api/v1/auth/authenticate with a valid username and password.

POST /api/v1/auth/authenticate

Content-Type: application/json

{
  "username": "your-username",
  "password": "your-password"
}

The API will respond with a JWT access token, which clients must include in the Authorization header of all subsequent requests.

HTTP/1.1 200 OK

Content-Type: application/json

{
  "token": "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9..."
}

By default, the API is configured to use the HS256 algorithm to sign and verify JWT tokens.

Health Checks and Monitoring

The API also includes Spring Boot Actuator for health checks and monitoring. The following endpoints are available:

/actuator/health: Returns the health status of the application.

/actuator/info: Returns custom application information (configured in application.properties).

By default, these endpoints are only available to authenticated clients.

Testing

To run the tests, you can use the following command:

mvn test

License

This project is licensed under the MIT License. See the LICENSE file for details.