Building REST APIs with Spring Boot: A Practical Guide

Building a REST API used to involve a lot of XML configuration in the old J2EE days. Spring Boot changed all that with auto-configuration. I can now spin up a production-ready API in under 10 minutes. The `@RestController` annotation combined with `@RequestMapping` makes endpoints declarative. One thing I learned the hard way: versioning. I didn’t version my first API, and when I changed the response structure, all the mobile apps broke. Now, I use URL versioning (`/api/v1/resource`) religiously. Also, don’t sleep on Spring Data REST. If you have a simple CRUD app, you can expose repositories directly as REST endpoints without writing a controller. But for complex business logic, you’ll want to keep the controller layer thin and delegate to a service layer. Validation is also key—use `@Valid` and Bean Validation to catch bad requests early.