spring-boot-event-driven-patterns

# Spring Boot Event-Driven Patterns ## Overview Implement Event-Driven Architecture (EDA) patterns in Spring Boot 3.x using domain events, ApplicationEventPublisher, `@TransactionalEventListener`, and distributed messaging with Kafka and Spring Cloud Stream. ## When to Use - Implementing event-driven microservices with Kafka messaging - Publishing domain events from aggregate roots in DDD architectures - Setting up transactional event listeners that fire after database commits - Adding async messaging with producers and consumers via Spring Kafka - Ensuring reliable event delivery using the transactional outbox pattern - Replacing synchronous calls with event-based communication between services ## Quick Reference | Concept | Description | |---------|-------------| | **Domain Events** | Immutable events extending `DomainEvent` base class with eventId, occurredAt, correlationId | | **Event Publishing** | `ApplicationEventPublisher.publishEvent()` for local, `KafkaTemplate` for distributed | | **Event Listening** | `@TransactionalEventListener(phase = AFTER_COMMIT)` for reliable handling | | **Kafka** | `@KafkaListener(topics = "...")` for distributed event consumption | | **Spring Cloud Stream** | Functional programming model with `Consumer` beans | | **Outbox Pattern** | Atomic event storage with business data, scheduled publisher | ## Examples ### Monolithic to Event-Driven Refactoring **Before (Anti-Pattern):** ```java @Transactional public Order processOrder(Order...