🚀 “Most developers use APIs every day… but very few actually understand how they work.” When I started with Spring Boot, I memorized things like: ✔ @RestController ✔ @GetMapping ✔ @RequestMapping I could build APIs. But if someone asked me: 👉 “What actually happens when a request hits your API?” …I didn’t have a clear answer. That’s when I realized: 👉 I was learning annotations 👉 But not understanding the flow 💡 Here’s the simple truth behind every REST API: It’s just a flow 👇 Client → Request → Mapping → Controller → Response 🧠 Let’s break it down simply: 🔹 @RequestMapping Routes the incoming request to the right method (Think: “Where should this go?”) 🔹 @RestController Handles the request and sends back response (Usually JSON — what frontend actually uses) 🔹 HTTP Methods • GET → Fetch data • POST → Create data • PUT → Update • DELETE → Remove 🔹 @PathVariable Takes value directly from URL Example: /users/101 🔹 @RequestParam Takes input from query Example: /search?keyword=phone ⚡ Why this matters (real world): When things break in production… Nobody cares if you know annotations. 👉 They care if you understand the flow 👉 They care if you can debug the request 👉 They care if you can fix it fast 💥 Big realization: > APIs are not about writing code. They’re about handling communication between systems. 📌 Simple shift that helps a lot: Don’t just ask: “How do I write this API?” Start asking: “Where does this request come from… and where does it go?” Because that’s where real backend thinking begins. 💬 Let’s test this: Can you clearly explain what happens from API request → response? Yes or still learning? 👇 #SpringBoot #Java #BackendDevelopment #RESTAPI #SoftwareEngineering #Developers #Coding #TechCareers #Programming #SystemDesign
Flow is everything. Most real debugging starts after the controller, not before it. Once you understand how DispatcherServlet, filters, interceptors, and service layers interact, tracing a failing request becomes much easier instead of guessing at annotations.
Yes — in Spring Boot: Client sends request → DispatcherServlet (Spring’s front controller) receives it → HandlerMapping maps it to the right @RestController method → Controller calls Service → Service interacts with Repository/DB → Response is converted to JSON (via Jackson) → Sent back to client 💡 Client → DispatcherServlet → Controller → Service → Repository → DB → JSON Response That’s the real flow behind every API 😀