IOBuildersBank - RESTful Banking Application

Table of Contents

• My Hexagonal Architecture approach
• Technologies Used
• Getting started
• Blockchain integration
• API

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My Hexagonal Architecture Approach

This project is designed using Hexagonal Architecture and DDD to ensure a clean separation of concerns and maintainability.

Bounded Contexts and Use Case Grouping

For each Bounded Context, such as User or Wallet:

• Business rules and use cases are encapsulated in a single service interface, implemented in the Application Layer. While individual use cases could be split into separate classes, I find it cleaner by grouping them into a service interface for each context, specially if the application scales too much.

Core Design Approach

1. Input/Output Encapsulation:

   • Input: Interfaces in the domain layer define use case interactions.
   • Output: Interfaces abstract external systems, in this case H2 database.

2. Infrastructure Implementations:

   • Interfaces are implemented in the infrastructure layer, allowing for easy replacement of external adapters without affecting the core logic.

3. Entity-DTO Mapping:

   • Mappers convert business logic entities and DTOs for input and output, maintaining separation between layers and preserving core domain independence.

Testing

• Unit Tests: Cover application services and input/output ports.
• Integration Tests: Verify end-to-end functionality in the Bootloader module with preinjected data.

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Technologies Used

• Java 17
• Spring Boot
• H2 Database
• BCrypt
• Spring Security
• JWT Authentication
• OpenApi 3.0
• Web3j
• Truffle and Ganache
• Maven

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Getting Started

Setup Instructions

1. Clone repository:

git clone https://github.com/santy117/IOBuildersBank.git
cd IOBuildersBank

2. Install dependencies:

mvn clean install

3. Run the application:

cd bootloader
mvn spring-boot:run

4. Access the API at http://localhost:8080

Access the API and H2 Database

• Base URL: http://localhost:8080
• H2 Console: http://localhost:8080/h2-console
  • Username: santiago
  • Password: iobuilders

Initialization Script

The application seeds the database with the following data:

• User:

  • Username: santisr117
  • Password: 123123 (password is stored in the database as a hash)

• Wallets:

  • wallet1: Balance 100.00
  • wallet2: Balance 50.00

These wallets are linked to the above user, and this data is used to test the integration tests and to allow an initial configuration of the bank application.

Password Hashing

For enhanced security, passwords are stored in the database as hashed values using BCrypt.

Blockchain Integration

I created a small integration with a local Ethereum blockchain using Ganache and Truffle for deploying and interacting with a simple smart contract that exposes a simple public view function and does not consume gas. This function is used to check the Ether balance of a specified address, and this functionality is completely separate from the rest of the application logic, it has only been created to test the integration with the blockchain, and the application mantains all the other functionalities if we don't set up the blockchain integration.

Steps to Set Up the Blockchain

1. Run the Local Blockchain (Ganache)

   • Start Ganache and click on Quickstart.
   • By default, Ganache will run on localhost:7545.

2. Deploy the Contract Using Truffle

   cd check-ether-contract
   truffle migrate

3. Update application.properties

   • After deployment, obtain the contract address and the private key of one of the accounts created in Ganache.
   • Update the following properties to your application.properties file:

     blockchain.contract.address=<your_contract_address>
     blockchain.credentials.privateKey=<your_private_key>

4. Launch the Application

   • Now that the blockchain is running and the contract is deployed, launch the application:

     mvn spring-boot:run

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API

The API uses JWT-based authentication.

Login

• Endpoint: POST /login Retrieves a token for the specified user. You can create first a new user or use the already created user:

Input parameters

parameter	type	example value	in	required
username	string	santisr117	query	true
password	string	123123	query	true

Sample response

{

"username": "santisr117",

"token": "eyJhbGciOiJIUzI1NiJ9.eyJzdWIiOiJzYW50aXNyMTE3IiwiaWF0IjoxNzMzMjI3MDkxLCJleHAiOjE3MzMzMTM0OTF9.98pu6n2Sf0K0YEiQveIySLu7mwnoZFk7bUsx6MPm_L0"

}

User

• Endpoint: POST /user

  Creates a new user. Input parameters

  parameter	type	example value	in	required
  Authorization	JWT	Bearer + JWT Token	Header	true

  Input Json

   {
  
   "username": "santisr117",
  
   "password": "123123",
  
   "email": "[email protected]"
  
   }

  Sample response Http Status 201: Created

• Endpoint: GET /user/{id}

  Get user info by id. Input parameters

  parameter	type	example value	in	required
  Authorization	JWT	Bearer + JWT Token	Header	true
  id	integer	1	Path	true

  Sample response

  	{
      "username": "santisr117",
      "email": "[email protected]",
      "id": 1,
      "wallets": [
          {
              "id": 1,
              "name": "wallet1",
              "balance": 115.00,
              "transactions": [
                  {
                      "id": 1,
                      "description": "transaction 1",
                      "date": "3/12/24 17:08",
                      "amount": 15.00
                  }
              ]
          },
          {
              "id": 2,
              "name": "wallet2",
              "balance": 50.00,
              "transactions": []
          }
      ]
  }

Wallet

• Endpoint: POST /wallet

  Creates a new wallet. Input parameters

  parameter	type	example value	in
  Authorization	JWT	Bearer + JWT Token	Header
  userId	integer	1	Query
  name	string	wallet 3	Query

  Sample response Http Status 201: Created

• Endpoint: GET /wallet/{id}

  Get wallet info by id. Input parameters

  parameter	type	example value	in	required
  Authorization	JWT	Bearer + JWT Token	Header	true
  id	integer	1	Path	true

  Sample response

  	{
      "id": 1,
      "name": "wallet1",
      "balance": 80.00,
      "transactions": [
          {
              "id": 1,
              "description": "tx1",
              "date": "3/12/24 17:08",
              "amount": 15.00
          },
          {
              "id": 2,
              "description": "Transfer to wallet 2",
              "date": "3/12/24 17:16",
              "amount": -50.00
          },
          {
              "id": 4,
              "description": "tx2",
              "date": "3/12/24 17:16",
              "amount": 15.00
          }
      ]
  }

• Endpoint: POST /wallet/{id}/deposit

  Makes a new deposit to a specified wallet id. Input parameters

  parameter	type	example value	in	required
  Authorization	JWT	Bearer + JWT Token	Header	true
  id	integer	1	Path	true
  amount	number	10	Query	true
  description	string	new deposit	Query	false

  Sample response Http Status 200: OK

• Endpoint: POST /wallet/{id}/transfer

  Makes a transfer from a source wallet to a specified wallet id. Input parameters

  parameter	type	example value	in	required
  Authorization	JWT	Bearer + JWT Token	Header	true
  id	integer	1	Path	true
  amount	number	10	Query	true
  target id	integer	2	Query	true

  Sample response Http Status 200: OK

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Blockchain

• Endpoint: GET /blockchain/balance

  Check the balance of a wallet address in the local blockchain. Input parameters

  parameter	type	example value	in	required
  Authorization	JWT	Bearer + JWT Token	Header	true
  walletAddress	string	0x0c642236ac09e6a4402921b5a9e6ae2f0a49f00c	Query	true

  Sample response

  	{
      "balance": 100
      }