Spring WebFlux is the reactive, non-blocking sibling of Spring MVC. Instead of one thread per request blocking on I/O, WebFlux runs on a small event-loop and frees the thread while it waits for the database or another service to answer. Built on Project Reactor, it’s a great fit for high-concurrency APIs and reactive data sources — but it’s not a free upgrade, and that nuance is the most important thing to get right. ...
Good Spring Boot exception handling means your API fails predictably. Out of the box, an unhandled exception gives the client either a wall of HTML (the Whitelabel Error Page) or a JSON blob that leaks your package names and stack trace. Both are bad: ugly for your frontend, and a small gift to attackers. The fix is to handle errors in one place with @RestControllerAdvice and return a consistent error body. Here’s the version I actually ship. ...
You want to ship an API. You don’t want to hand-configure Tomcat, write a web.xml, or fight a servlet container. A Spring Boot REST controller gets you from zero to a working HTTP endpoint in about five minutes — and this guide is the copy-paste-run version, plus just enough explanation that you actually understand what you pasted. What you need first One dependency: spring-boot-starter-web. Add it to your pom.xml (or build.gradle) and Spring Boot pulls in Spring MVC, Jackson (for JSON), and an embedded Tomcat. That last part is the magic — there’s no external server to install or deploy to. Your app is the server. Generate a skeleton at start.spring.io if you don’t have one (more on that in Surviving Day 1 with Spring Boot 3). ...