Bank Application – Microservices Architecture

A fully functional Banking System built using Spring Boot Microservices, Eureka Service Registry, API Gateway, MongoDB, Docker, and Resilience4j Circuit Breakers.

This system supports:

• Creating bank accounts
• Deposits, Withdrawals, Transfers
• Storing transaction history
• Sending notifications
• Service discovery & load balancing
• Fault tolerance with circuit breakers

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📌 Microservices Included

Service	Port	Description
Eureka Server	8761	Service registry & discovery
API Gateway	8080	Routes incoming client requests
Account Service	8081	Manages account creation & balance updates
Transaction Service	8082	Handles deposit/withdraw/transfer
Notification Service	8083	Sends transaction notifications
MongoDB	27017	Shared database container

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Architecture Diagram

🛠 Tech Stack

• Java 17
• Spring Boot 3
• Spring Cloud Netflix Eureka
• Spring Cloud Gateway
• MongoDB
• RestTemplate
• Resilience4j Circuit Breaker
• Docker & Docker Compose
• SLF4J + Logback Logging
• JUnit + Mockito

📂 Project Structure

BankApp-Microservices/
 ├── Eureka-Server/
 ├── ApiGateway/
 ├── Account-Service/
 ├── Transaction-Service/
 ├── Notification-Service/
 ├── docker-compose.yml
 └── README.md

⚙️ How to Run the Project

1️⃣ Run Locally (Without Docker)

Step 1: Start Eureka Server

cd Eureka-Server
mvn spring-boot:run

Step 2: Start other services

Run each

cd Account-Service       → mvn spring-boot:run
cd Transaction-Service   → mvn spring-boot:run
cd Notification-Service  → mvn spring-boot:run
cd ApiGateway            → mvn spring-boot:run

Step 4: Open Eureka Dashboard

http://localhost:8761

2️⃣ Run with Docker Compose (Recommended)

Step 1: Build all services

Every service should include a Dockerfile:

FROM eclipse-temurin:17-jdk
COPY ./target/*.jar app.jar
ENTRYPOINT ["java","-jar","app.jar"]

Step 2: Run Docker Compose

Step 2: Run Docker Compose

Step 3: Verify services

docker ps

📮 API Endpoints

🏦 Account Service

Create Account

POST /api/accounts

Update Balance

PUT /api/accounts/{accNo}/balance

Activate/Deactivate Account

PUT /api/accounts/{accNo}/status

Get Account

GET /api/accounts/{accNo}

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💸 Transaction Service

Deposit

POST /api/transactions/deposit

Withdraw

POST /api/transactions/withdraw

Transfer

POST /api/transactions/transfer

List Transactions

GET /api/transactions/{accNo}

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🔔 Notification Service

Send Notification

POST /api/notifications/send

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🛡️ Fault Tolerance (Circuit Breakers)

Used in TransactionService:

• If Account-Service is down → fallback creates a FAILED transaction.
• If Notification-Service is down → fallback logs a warning.
• Ensures the system remains stable and never fully crashes.

🧪 Testing

Each service includes:

• Unit tests using JUnit + Mockito
• Mock service tests
• Circuit breaker fallback tests
• REST controller tests using RestTemplate

Run all tests:

mvn test

📝 Logging

• All services use SLF4J + Logback
• API Gateway logs every incoming request
• Transaction Service logs every deposit, withdrawal, and transfer
• Notification Service logs every message sent