ISO 20022 Payment Processing System

A Java-based payment processing backend built with Spring Boot, featuring secure REST APIs, transaction management, and ISO 20022 financial messaging.

Project Overview

The ISO 20022 Payment Processing System is a backend application developed using Java 21 and Spring Boot 3 to demonstrate payment processing workflows and standardized financial messaging. It provides RESTful APIs for handling payment requests, validating transaction data, tracking payment records, and generating ISO 20022-style XML messages.

The application follows a layered architecture that separates controllers, services, repositories, DTOs, and domain entities. It also incorporates Spring Security, JWT-related authentication components, centralized exception handling, API documentation, automated tests, and Docker configuration. This project serves as a practical exploration of backend engineering and financial technology concepts.

Key Features

• Payment processing through RESTful APIs.
• ISO 20022 message generation for pain.001, pacs.008, and camt.053.
• Spring Security and JWT-related security components.
• Payment request validation and transaction management.
• Spring Data JPA and Hibernate for database access.
• Centralized exception handling and structured error responses.
• Swagger/OpenAPI API documentation.
• Spring Boot Actuator health and monitoring endpoints.
• Unit and controller testing.
• Docker and Docker Compose configuration.

Technology Stack

Category	Technologies
Programming Language	Java 21
Backend Framework	Spring Boot 3
API Development	Spring Web, REST APIs
Security	Spring Security, JWT
Persistence	Spring Data JPA, Hibernate
Database	H2 for development; MySQL configured for the production profile
Financial Messaging	ISO 20022
API Documentation	Swagger/OpenAPI
Monitoring	Spring Boot Actuator
Build Tool	Maven
Containerization	Docker, Docker Compose
Testing	Spring Boot Test, JUnit

System Architecture

The application uses a layered backend architecture to separate responsibilities and make the code easier to maintain and extend.

Client / API Consumer
        |
        v
REST Controllers
        |
        v
Service Layer
        |
        +----------------------+
        |                      |
        v                      v
Payment Processing      ISO 20022 Message
        |                 Generation
        v
Repository Layer
        |
        v
Configured Database

ISO 20022 Financial Messaging

The project explores the following ISO 20022 message types:

• pain.001: Customer credit transfer initiation.
• pacs.008: Financial institution-to-financial institution customer credit transfer.
• camt.053: Bank-to-customer statement.

These message generators demonstrate the structure and purpose of standardized financial messages. Additional schema validation and integration testing would be needed before using generated messages with real financial institutions.

Getting Started

Prerequisites

• Java Development Kit (JDK) 21
• Maven
• Git
• Docker Desktop (optional)

Clone the Repository

git clone https://github.com/Sam-k-001/ISO20022-Payment-Processing-System.git
cd ISO20022-Payment-Processing-System

Build the Project

mvn clean verify

Run the Application

mvn spring-boot:run

The application is configured to run on port 8080 by default. Check the application configuration for the active profile and database settings.

API Documentation

After starting the application, try these URLs if enabled by the current configuration:

• Swagger UI: http://localhost:8080/swagger-ui.html
• OpenAPI JSON: http://localhost:8080/api-docs
• Application Health: http://localhost:8080/actuator/health

Authentication requirements depend on the configured Spring Security rules.

Testing

Run the automated test suite with:

mvn test

Run the complete Maven verification lifecycle with:

mvn clean verify

Docker

The repository contains Docker-related configuration under the docker/ directory. Review the Dockerfile, Compose build context, database credentials, and environment variables before starting the containerized application.

Never commit real passwords, JWT secrets, or production credentials to the repository.

Project Roadmap

The following improvements are planned and should be marked complete only after implementation and testing:

• PostgreSQL and Flyway database migrations.
• Kafka-based asynchronous payment processing.
• Idempotent payment processing and reliable event handling.
• Double-entry ledger service.
• Fraud detection service.
• Settlement and reconciliation workflows.
• Additional ISO 20022 messages: pacs.002, pain.002, camt.056, and pacs.004.
• Prometheus and Grafana monitoring.
• GitHub Actions CI/CD pipeline.
• Kubernetes deployment.
• AWS deployment.

Project Scope

This is an educational and portfolio project intended to demonstrate backend development, payment workflow concepts, and financial messaging. It is not a production banking platform and should not be used to process real payments or sensitive customer data without substantial additional engineering, security review, compliance validation, and testing.

License

This project is licensed under the MIT License. See the LICENSE file for details.