Implementing API Key Authentication for REST APIs with Spring Security

A DEV Community guide explains how to add API key authentication to stateless REST APIs using Spring Security. It points out that the default session-based, form-login setup, with its CSRF tokens and cookies, is a poor fit for JSON endpoints consumed by internal tools, mobile apps, and partners. The recommended approach is a simple secret key sent in a request header, which is easier to generate, rotate, and audit than OAuth or JWT. The tutorial covers a custom authentication token and provider, a filter chain that extracts the key, and secure storage with hashing and rotation. It also addresses testing, common pitfalls such as leaking keys in logs, and production hardening like rate limiting, revocation, and monitoring.