J. POO Morgan Chase & Co. - OOP Banking System

Description

• Implemented a simplified banking system that allows users to create accounts, deposit money, transfer money between accounts, create transactions, view their account balance etc.
• The system is implemented using multiple design patterns such as Factory, Command, Builder and Strategy to manage the different possible commands and types of objects.

Solution Components

Bank

• Role: Stores all the user's information, reading the input data, creating the user list, exchange rates list, setting up the bank's currency exchange mechanism, the alias hashmap, the split payment context hashmap and executing the commands.
• The class also contains methods for getting a commerciant by its name or iban, an account by a given card number or iban, a card object by a given card number and a user object by its email, as well as getters and setters for each field.
• A split payment context is also created for each transaction that is a split payment, containing the transaction's information and the list of the users that are involved in the split payment.
• Relationships: Interacts with User, ExchangeRates, Commerciant, CurrencyConverter and ProcessCommands to manage the bank's operations.

User

• Role: Represents a user of the bank, containing a list of accounts and its personal information such as name, email, occupation, birthdate and his account's plan type. His age is calculated based on his birthdate and the current date, using the class AgeCalculator.
• Relationships: Interacts with Account, Plan and AgeCalculator to manage the user's accounts and information.

ExchangeRate, Commerciant and CommandData

• Role: The classes hold information on the exchange rates between different currencies and the rate for the bank's transactions, on the commerciants and on the different commands.
• Relationships: The classes interact with CurrencyConverter to manage the exchange rates, Bank to manage the commerciants and with the command classes to get the command's information.

Account, ClassicAccount, SavingsAccount, BusinessAccount and AccountFactory

• Role: The classes represent an account in the bank, containing the account's balance, iban, currency etc. and lists of the account's cards and transactions.
• All classes inherit Account, SavingsAccount and BusinessAccount having additional fields and methods for their specific account type. Account also has methods for updating the total spent and the number of transactions made at a given commerciant and for handling money transactions.
• AccountFactory is a Factory class that creates new accounts based on the account type.
• Relationships: Interacts with Card, Transaction, User, Commerciant to manage the account's operations.

Card and OneTimeCard

• Role: The classes represent a card associated with an account, containing the card's number, parent account and the card's state.
• OneTimeCard inherits Card and is a card that can be used only once (its card number is regenerated after each payment).
• The classes contain a method for handling the transactions after payment, which is only implemented for OneTimeCard.
• Relationships: Interacts with Account to store the card's parent account.

CurrencyConverter

• Role: Represents the currency exchange mechanism of the bank, containing the exchange rates in a graph and a method for converting money between different currencies.
• The conversion is realised using a graph of the exchange rates and currencies and the DFS algorithm.
• Relationships: Interacts with ExchangeRates to manage the exchange rates.

Transaction, TransactionBuilder and PrintTransactionsJSON

• Role: Creates a transaction object which contains different information based on the transaction type.
• I used the Builder pattern because each transaction has three default fields (timestamp, description and type) and the other fields are optional.
• PrintTransactionsJSON is a class that prints each transaction in JSON format and also contains methods for printing reports and spendings reports in JSON format.
• Relationships: PrintTransactionsJSON interacts with Transaction to print the transactions in JSON format.

Command classes (AddAccount, CreateCard, PrintUsers etc.)

• Role: The classes represent the commands that can be executed by the bank, each command having a method for executing it.
• Each command is created with the Command and Factory patterns (using the CommandFactory class).
• Each command implements a Command interface and contains the execute method which does all the operations needed for the command.
• The command's errors are printed to the JSON ArrayNode by throwing a JSONExceptions exception that is caught in the CommandInvoker class and printed through the PrintJSONMessages class.
• Relationships: Interacts with Bank, CommandData and ArrayNode to execute and print the command.

Cashback implementation (CashbackContext, CashbackStrategy and its subclasses)

• Role: The classes represent the cashback mechanism of the bank, creating a cashback context for each transaction that can get cashback and using the Strategy pattern to create different cashback methods.
• The CashbackContext class contains methods for creating and applying the cashback strategy, based on the commerciant's strategy.
• NrOfTransactions and SpendingThreshold are the two cashback strategies implemented, each overriding the interface's method for calculating the cashback amount.

Usage of the given fileio classes

• I used the fileio classes to populate my arrays with the given UserInput, ExchangeInput and CommerciantInput data. I used an CommandInput array to create my CommandData objects which are used for executing the commands.