ddd

In test driven development, model 'place order' intent with static factory, private constructor, and OrderState enum. Advantages over mutable setters, trade-offs, DDD tips, and TDD code examples for Java design patterns.

Learn microservices patterns to combine Order and Payment in a single service using modular monolith, bounded contexts, ports-and-adapters, and saga patterns for clean boundaries and easy future extraction into independent microservices.