CQRS Example based on Microservices Architecture and Event Sourcing

Overview

This project demonstrates a very basic bank ledger system using the CQRS (Command Query Responsibility Segregation) pattern, microservices architecture, and event sourcing. Instead of using a messaging system with a JMS provider, Spring Application Events are utilized, and persistence is managed in a HashMap.

The project is a work in progress and will continue to evolve over time. All changes and updates will be logged in the ChangeLog.md file.

TODOs

• Implement logging using @slf4j for better monitoring and troubleshooting.
• Implement Exception Handling.
• Integrate Swagger for API documentation, or alternatively, use Spring Boot Actuator to expose endpoints.
• Implement projections on the read/view side to optimize query performance and support complex read operations.
• Resolve potential duplicate declarations in the POM(s).
• Explore containerization options once a messaging bus is introduced.

How to Run

To run the project:

1. Checkout the repository.
2. Navigate to the cqrs-account-service module.
3. Run the CqrsServiceApplication from IntelliJ IDEA.

Endpoints (Write Side / Command Pillar)

Deposit

curl --location 'localhost:8080/transactions/deposit/971a09db-5d99-4c90-9064-23ff972efb3b' \
--header 'Content-Type: application/json' \
--data '{
"amount": "200.00"
}'

Withdraw

curl --location 'localhost:8080/transactions/withdraw/971a09db-5d99-4c90-9064-23ff972efb3b' \
--header 'Content-Type: application/json' \
--data '{
"amount": "100.00"
}'

Endpoints (Read Side / View Store)

Balance

curl --location 'localhost:8080/accounts/balance/971a09db-5d99-4c90-9064-23ff972efb3b'

Transactions

curl --location 'localhost:8080/accounts/transactions/971a09db-5d99-4c90-9064-23ff972efb3b?noOfTransactions=20'

Enjoy exploring the functionalities!