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 endpoint with the out‑of‑the‑box configuration, you quickly hit a wall: CSRF tokens, redirects, and HttpSession objects start leaking into your API contract, forcing clients to handle cookies they never asked for.

The pragmatic solution is to replace the heavyweight OAuth dance or JWT boilerplate with a simple API key. An API key is just a secret string that a client includes in each request, typically via a header. It’s easy to generate, rotate, and audit, and it works flawlessly with Spring’s filter chain.…