🧪 Order Management Demo Project

A microservices-based demo project demonstrating an order and payment workflow.
Focus areas include inter-service communication patterns (sync & async) and RabbitMQ as the primary message broker for decoupled event handling.

⚙️ Tech Stack: Java 21, Maven, Spring Boot, Spring Data JPA, Spring Cloud Config, RabbitMQ, PostgreSQL, Redis, Lombok, MapStruct, Jackson (FasterXML)

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📦 Microservices Overview

Service Name	Description
Config Server	Provides centralized configuration for all microservices.
Order Service	Manages order creation, order-related data, and the order validation process.
Accounting Service	Handles verified order costs and redirects them to the payment and billing services.
Product Service	Manages product stock availability and updates stock data.
Discount Service	Validates and applies discount codes to orders.
Billing Service (Planned)	Manages the billing process for verified and completed orders.
Payment Service (Planned)	Provides the payment processing for validated orders.

A common module is used to gather shared tools such as Lombok, MapStruct, Jackson (FasterXML), and Spring AMQP for managing RabbitMQ schemas.

📬 RabbitMQ Schema

Current exhanges and queues:

Exchange Name	Type	Queue Name	Publisher Service	Consumer Service	Routing Key	Purpose
x.order.validation	Fanout	q.stock.validation.stock	order-service	product-service	N/A	Publishes order stock validation request
x.order.validation	Fanout	q.stock.validation.discount	order-service	discount-service	N/A	Publishes discount validation request
x.validation.response	Fanout	q.validation.response	order-service	accounting-service	N/A	Publishes combined validation results
x.validation.response.wait	Fanout	q.validation.response.wait	order-service	order-service	N/A	Retry queue for delayed validation responses
dlx.validation.response	DLX	q.order.rejected	N/A	not determined	N/A	Dead-letter queue for failed validations
x.accounting.price	Direct	q.accounting.price	N/A	not determined	q.accounting.price	Publishes validated order to be priced
x.payment	Topic	q.payment.credit-card	accounting-service	payment-service	payment.card	Publishes priced order to credit card payment
x.payment	Topic	q.payment.bank-transfer	accounting-service	payment-service	payment.bank-transfer	Publishes priced order to bank transfer payment
x.payment	Topic	q.payment.wallet	accounting-service	payment-service	payment.wallet.*	Publishes priced order to digital wallet payment

📝 Notes :

• x.validation.response.wait is the dead-letter exchange (DLX) target of q.validation.response. When the retry count is exceeded, messages are forwarded to q.order.rejected via the dlx.validation.response.

🔄 Workflow

1. Order Acceptance

The order-service accepts an order via REST API. the Order Request includes a discount code (optional) and a cart with one or more items (product IDs and requested quantities)

• The discount code is sent to the discount-service for validation.
• The cart is sent to the product-service to check product stock availability.

2. Validation

discount-service and product-service validates the order and both services return their validation results to the order-service.

• Both services forward validation results to order-service.
• The discount-service validates the discount code.
• The product-service validates the stock availability.

3. Validation Handling

order-service collects validation results forwards the order record to accounting-service if validations succeed

• Collects both validation responses using the Order ID as a correlation key.
• Validation results are temporarily stored in an in-memory cache until both are received.
• If both discount and stock validation succeed, forwards the order record to accounting-service in order to determine and calculate prices ant total cost.
• If either validation fails, the order is rejected immediately.

4. Accounting and Pricing

accounting-service determines prices of products in the cart and calculate total cost.

• Retrieves product prices via a REST API call.
• Retrieves the discount amount via a REST API call.
• Calculates total prices and applies discount
• Forwards priced order to payment-service and billing service (Planned)

5. Payment Processing (Planned)

The payment-service will handle the actual payment process based on the chosen payment method.

6. Billing (Planned)

The billing-service will store the final priced order and payment details, which can be queried via an API.