My assignment

The solution

The solution consist of 3 main classes: TransferController, TransferService, TransferRepositoryInMemory.

• TransferController - a Spring REST controller responsible for handling incoming HTTP POST requests to initiate money transfers. It receives and validates a TransferRequest object containing details of the transfer, such as source and destination account IDs and the transfer amount. It then delegates the transfer request to the TransferService, logs the request, and returns a response containing a TransferResponse.
• TransferService - class facilitates money transfers between accounts. It validates transfer input parameters and checks for sufficient account balances before executing a transfer through the transferRepository. After a successful transfer, it logs the transaction, notifies both the sender and receiver about the transfer, and returns a transfer response. If the transfer cannot be executed, it handles exceptions and provides appropriate error responses.
• TransferRepositoryInMemory - class is responsible for managing and facilitating money transfers between accounts in a multi-threaded environment. It uses a ConcurrentHashMap to store records of transfers. Additionally, it employs ReentrantLocks to prevent potential deadlocks when transferring funds between accounts by acquiring and releasing locks in a controlled order.

Notes:

The repository contains 2 commits:

• initial commit - the version of the application given to me
• dws challenge - the solution for the given task