"Why is my API returning HTML error pages?!" I stared at my console in disbelief. My React frontend was trying to parse JSON, but Spring Security was happily serving up a Whitelabel Error Page for failed authentication attempts. This took me 3 hours to fix. Let me show you how to make Spring Security play nice with modern frontends. 🎨✨
"My login endpoint is returning 403 Forbidden! But I configured it as .permitAll() in SecurityConfig! Why is the JwtFilter still blocking it?" I spent 2 hours debugging this. Turns out, I had a fundamental misunderstanding of how Spring Security works. The JwtFilter doesn't "skip" endpoints - it runs on EVERYTHING. Let me explain the magic. 🎩✨
"Why do we need both generateToken() (public) and createToken() (private) instead of just one method?" Because separation of concerns makes your code extensible. The public method handles what claims to add (business logic), while the private method handles how to build the JWT (technical details). This lets you add new token types without repeating code. Let's understand why this design pattern is essential.
Want to implement JWT authentication in Spring Boot? You need three dependencies, not one. Here's why and what each one does.