Spring Security API key authentication for REST APIs tutorial — Complete Guide A practical, in-depth guide to Spring Security API key authentication for REST APIs tutorial with examples. INTRO Every day we ship micro‑services that expose JSON endpoints to internal tools, mobile apps, or third‑party partners. The default Spring Security setup assumes a session‑based, form‑login flow—perfect for web UIs but a poor fit for stateless APIs. When you try to protect a REST endpo...