Banking System API

A Spring Boot REST API for a simple banking system with authentication, account management, deposits, withdrawals, and transaction tracking.

This project demonstrates backend development skills including:

• Spring Boot REST APIs
• Spring Security (JWT authentication)
• JPA/Hibernate ORM
• MySQL database integration
• Docker containerization

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Features

• User authentication (JWT secured)
• Create bank accounts
• Deposit and withdraw funds
• Transaction history tracking
• Pagination and filtering of transactions
• Global exception handling
• Input validation

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API Endpoints

➤ Auth

• POST /auth/register
• POST /auth/login

➤ Bank Operations

• POST /bank/create
• POST /bank/deposit
• POST /bank/withdraw

➤ Transactions

• GET /bank/{accNo}/transactions

Query params:

• type
• start
• end
• page
• size

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Response Format

{
  "status": "success",
  "message": "Transactions retrieved",
  "data": [...]
}

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Error Handling

All errors follow a consistent structure:

{
  "status": "error",
  "message": "Account not found",
  "data": null
}

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Sample Request(s)

POST /bank/create

{ "accountNumber": "540", "accountName":"Henry", "initialDeposit": 5000 }

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Key Concepts Implemented

• JPA Entity Relationships (@OneToMany, @ManyToOne)
• DTO Mapping
• Java Streams (filtering, sorting, pagination)
• Global Exception Handling
• Validation

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Future Improvements

• Add unit & integration tests
• Add CI/CD pipeline
• Improve security (refresh tokens, roles)
• Add Swagger API documentation
• Add Redis caching

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Recent Updates

Account Creation Refactor

• Implemented DTO-based request handling using CreateAccountRequest
• Added validation with Jakarta Validation annotations
• Improved separation between API requests and database entities

Database & Entity Improvements

• Refactored BankAccount entity structure
• Separated internal database ID (Long id) from business account number (String accNo)
• Added proper auto-generated primary keys using JPA/Hibernate
• Added unique constraints for account numbers

Persistence Layer Enhancements

• Updated repository structure to use JpaRepository<BankAccount, Long>
• Added custom repository method:

  findByAccNo(String accNo)

• Fixed Hibernate schema generation and table mapping issues

Validation & Error Handling

Added custom exceptions:

• InvalidAmountException
• ResourceNotFoundException

Implemented request validation for:

• account names
• balances
• deposits
• withdrawals

Security Improvements

• Integrated Spring Security authentication context handling
• Added ownership validation logic for secured account operations
• Improved access control structure for protected endpoints

Transactions API

• Added transaction filtering by:
• transaction type
• date range
• Added pagination support
• Added transaction sorting by latest activity

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Tech Stack

• Java 21
• Spring Boot
• Spring Security (JWT)
• Spring Data JPA
• Hibernate
• MySQL8
• Docker & Docker Compose
• Maven

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Project Setup (Local Development)

1. Clone the repository

git clone https://github.com/johnmacha/Banking-System-Api.git
cd banking_system

2. Configure database

• Update application.properties : spring.datasource.url=jdbc:mysql://localhost:3306/Bank spring.datasource.username=root spring.datasource.password=my_password

3. Run the application

./mvnw spring-boot:run

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Running with Docker

1. Build the application

./mvnw.cmd clean package -DskipTests

2. Start containers

docker compose up --build

• This will start:

Spring Boot API → http://localhost:8080 MySQL Database → port 3307 (host)

Docker Architecture

Spring Boot (banking-api) │ ▼ MySQL (banking-mysql)

-Communication inside Docker: jdbc:mysql://mysql:3306/Bank

Environment Variables (Docker)

• Configured in docker-compose.yml :

SPRING_DATASOURCE_URL=jdbc:mysql://mysql:3306/Bank SPRING_DATASOURCE_USERNAME=root SPRING_DATASOURCE_PASSWORD=my_password

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Docker Services

MySQL

• Image: mysql:8.0
• Port: 3307 (host) → 3306 (container)
• Database: Bank

Banking API

• Spring Boot container
• Port: 8080

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Author

John Macharia