Dabaoshi

Aug 9, 2026 · Fundamentals

Observer Pattern: Decoupling Order Payment Success Actions via Publish‑Subscribe

The article explains the Observer pattern by first showing the problems of hard‑coding post‑payment actions, then detailing how defining a subject, observer interface, and concrete observers decouples the system, discusses push vs pull notification models, and illustrates real‑world uses in Spring events, GUI listeners, and message queues.