chuyennm / virtual-wallet

Building a Java library for online banking platform to build the virtual wallet to track users transaction account.

About

This project is about Building a Java library for online banking platform to build the virtual wallet to track users transaction account.

This is a spring boot application with in memory database H2. I am using JPA(Java Persistance API) to interact with the in memory database.

Problem Statement

Infiniti Space Bank is launching a brand new online banking platform and they want us to build a Java library to build the virtual wallet to track users transaction account. https://en.wikipedia.org/wiki/Transaction_account . At a high level the library needs to solve the following business needs

• Track a user’s account balance
• Manage account transactions in the form of debits (withdrawals) and credits (deposits).
• Allow a user to transfer money to another user/account.
• Keep a history of last N transactions.

UML Diagram

Following UML diagram indicates the database tables and thier interaction which I am using.

How to run the project

Following steps illustrate procedures you need to follow to run the code :

Step 1 : Download the repository

$ git clone https://github.com/saurabhsingh13no/virtual-wallet.git
$ cd virtual-wallet

Step 2 : Build the project using maven

$ mvn clean install

Step 3 : run the project

$ mvn spring-boot:run

• Now navigate to http://localhost:8080/ . You would see something like below index.html page :

Congratulations. You have successfully cloned the repo.

• Note : If you want to check the test coverage, open the project in IntelliJ and right click on project and click run with coverage>All tests

Functionality

Since project uses H2 in-memory database, some sample data has already been provided to get started with. Below are snapshot of data that already exists in the table :

• You can see the entries in the table for yourself. Navigate to http://localhost:8080/h2-console .You would see below screen :

Make sure that you use jdbc:h2:mem:testdb as JDBC URL. Click connect.

Enter below select queries to see the output :

select * from customer;
select * from wallet;
select * from account;
select * from bank_transaction;

Press ctrl+enter.

Now, I think you are all set up. Lets see what this library can do :

• a) Add an account to user 4 (Dan in this case) :

Provided endpoint : http://localhost:8080/api/account/

use post request as :

{
	"balance":4000,
	"accountHolder" : {
		"userId": 4,
		"fname" : "Dan",
		"lname":"Brown",
		"email" :"dan@brown"
	}
}

We can now check that Account 3001 is now associated with userId 4 and no wallet:

• b) Create a new wallet for a user :

I am assuming a user can have multiple accounts.

Provided endpoint for creating new wallet :

http://localhost:8080/api/wallet/{customerId}

I used Postman for this, since it provides easy interface for sending post request.

e.g. Lets create a wallet for ** Dan Brown** our 4th user in the database. We would post request to http://localhost:8080/api/wallet/4 using below JSON format :

You can now check, that wallet 4 is now associated with user 4 :

• c) Return current account balance :

Provided endpoint : http://localhost:8080/api/wallet/{walletId}/account/{accountId}/balance.

e.g Let us check balance for User 1 and associated account number 1000. We would use a GET request to http://localhost:8080/api/wallet/1/account/1000/balance. Below is the output from postman :

The backend JAVA code checks for all validation. If the accountId is not associated with provided walledId, an exception is thrown.

• d) Perform a withdrawal transaction on an account :

Provided endpoint : http://localhost:8080/api/wallet/{walletId}/account/{accountId}/withdraw/{amount}

Allows one to withdraw amount from account associated with wallet.

e.g. Lets withdraw $100 from accountId 1000 associated with walletId 1. I use POST request to http://localhost:8080/api/wallet/1/account/1000/withdraw/100 in Postman. Following is the output :

We can now check that $100 was actually withdrawn from the account as is reflected in the database :

• e) Perform a deposit transaction on an account :

Provided endpoint : http://localhost:8080/api/wallet/{walletId}/account/{accountId}/deposit/{amount}

Allows one to deposit amount into an account associated with a wallet.

e.g. Lets deposit $200 to accountId 1000 associated with walletId 1. I use POST request to http://localhost:8080/api/wallet/1/account/1000/deposit/200 in Postman. Following is the output :

We can now check that account 1000 does have a new deposit of $200 by running select query on table account :

• f) Perform a transfer from one account to another account :

Provided endpoint : http://localhost:8080/api/wallet/{walletId}/account/{trasferFromAccountId}/transfer/wallet/{toWalletId}/account/{transferToAccountId}/amount/{amount}.

Allows one to transfer money from one account in one wallet to another account in another wallet.

e.g. Let us transfer $150 from accountId 1000 associated with walletId 1 to accountId 2000 associated with wallet 2 . I use a POST request to http://localhost:8080/api/wallet/1/account/1000/transfer/wallet/2/account/2000/amount/150 in Postman. Following is the output :

Let us confirm the transfer by checking in the database :

• g) Return last N transactions for an account :

Provided endpoint : http://localhost:8080/api/wallet/{walletId}/account/{accountId}/lastNTransactions/{n}.

Allows one to check their respect transaction statement.

e.g. Let us check for last 3 transactions for accountId 1000 associated with walletId 1. I use a GET request to http://localhost:8080/api/wallet/1/account/1000/lastNTransactions/3 in Postman. Following is the output :