Handle Failure with a Global Exception Handler in Spring Boot

Most developers return wrong HTTP status codes. Here's the correct way 👇 I see this mistake constantly in code reviews: return ResponseEntity.ok(null); // ❌ Wrong for errors return ResponseEntity.ok("User deleted"); // ❌ Wrong for DELETE The correct way: ✅ 200 OK — GET request success, data returned ✅ 201 CREATED — POST success, resource created ✅ 204 NO CONTENT — DELETE success, nothing to return ✅ 400 BAD REQUEST — Invalid input from client ✅ 401 UNAUTHORIZED — Not logged in ✅ 403 FORBIDDEN — Logged in but no permission ✅ 404 NOT FOUND — Resource doesn't exist ✅ 409 CONFLICT — Duplicate data (email already exists) ✅ 500 INTERNAL SERVER ERROR — Something broke on server Spring Boot example: return ResponseEntity.status(HttpStatus.CREATED).body(savedUser); Correct status codes make your API professional, predictable, and frontend-developer friendly. Save this. Share with your team. Which status code do you see misused most? 👇 #SpringBoot #RestAPI #Java #BackendDevelopment #APIDesign

Stop rewriting the same authentication and payment logic for every new Java project. Two months ago, I shared the architectural vision for a modern Java SaaS boilerplate. Today, I am officially open-sourcing the core Community Edition of the ZukovLabs Enterprise Starter Kit! I’ve built this to save developers 200+ hours of initial setup. It’s not just a toy project; it’s a production-ready foundation built on enterprise patterns. What’s inside the Open-Source Core? - Backend: Java 21, Spring Boot 3.4.1, Spring Security (JWT) - Frontend: Angular 21 (Standalone Components, Material UI) - Database: MSSQL, Flyway Migrations - Infrastructure: Fully Dockerized (DB + Backend + Frontend in one command) No legacy nonsense. Just clean, scalable architecture. - Grab the Open-Source code here: https://lnkd.in/db86fZrY (P.S. The attached video showcases the full PRO version. PRO is a complete business engine that adds: ✅ Full Stripe Billing (Checkout, Webhooks, Portal) ✅ Passwordless Auth (Magic Links & Auto-login) ✅ Strict 3-Tier RBAC & Tenant Data Isolation (403 Enforcement) ✅ IP Rate Limiting (Brute-force protection) ✅ Server-Side Pagination & Angular Signal Caching ✅ Async HTML Email Service (Thymeleaf) ✅ Chart.js Analytics Dashboard ✅ 88 Strict Tests (Mockito, Vitest, ArgumentCaptor) 👇 Link to skip the 200h setup and get PRO is in the comments!) #Java #SpringBoot #Angular #SaaS #SoftwareEngineering #OpenSource #BuildInPublic

🚨 Stop guessing API errors. Read them like a pro. Ever spent 30 minutes debugging… just to realize it was a 400 Bad Request? 😅 👉 Understanding HTTP status codes is not optional. It’s a superpower for every backend & full stack developer. ⚡ API Status Codes — what they REALLY mean: 🟢 2xx = You’re good ✔️ 200 → Everything worked ✔️ 201 → Resource created ✔️ 204 → Success, no content 🔵 3xx = Look somewhere else ➡️ 301 → Permanent redirect ➡️ 302 → Temporary redirect ➡️ 304 → Use cache 🟡 4xx = You messed up (client side) ⚠️ 400 → Bad request (invalid input) 🔐 401 → Not authenticated ⛔ 403 → Not allowed 🔍 404 → Not found ⚡ 409 → Conflict 🧪 422 → Validation failed 🚦 429 → Too many requests 🔴 5xx = Server is crying 💥 500 → Internal error 🌐 502 → Bad gateway 📉 503 → Service unavailable ⏳ 504 → Timeout 🧠 Debug faster with this mindset: ✔️ 2xx → Relax, it’s working ✔️ 3xx → Check URL / caching ✔️ 4xx → Fix your request ✔️ 5xx → Check logs + backend 🔥 Real talk: If you’re building APIs with Spring Boot, Node, or microservices, mastering this = faster debugging + better systems + less stress 💬 Be honest… Which status code wastes most of your time? 😅 #API #Backend #Java #FullStack #WebDevelopment #Debugging #SoftwareEngineering #Microservices #DevTips

Understanding HTTP Status Codes Today I focused on an important concept in backend development — HTTP Status Codes While building REST APIs, it’s not just about sending data, but also about sending the right response to the client. 🔹 Learned about different categories of status codes: • 2xx (Success) – 200 OK, 201 Created • 4xx (Client Errors) – 400 Bad Request, 404 Not Found • 5xx (Server Errors) – 500 Internal Server Error 🔹 Understood when to use each status code in real APIs 🔹 Implemented status handling using "ResponseEntity" in Spring Boot This helped me realize how APIs communicate clearly with frontend applications and handle errors properly. Small concept, but very powerful in building real-world applications. Next step: Improving API structure and adding more real-world logic. #Java #SpringBoot #BackendDevelopment #RESTAPI #CodingJourney

RestTemplate vs WebClient - which one should you use? I used to think this was a simple choice. At one point, I also assumed switching to WebClient would automatically improve performance but in most cases I’ve worked on, the real bottleneck was somewhere else. 🔹 RestTemplate • Simple and easy to use • Works well for synchronous flows • Good enough for most traditional applications But: • Blocking by nature • Can become a bottleneck under high load 🔹 WebClient • Non-blocking and reactive • Better for high-concurrency systems • More efficient resource utilization But: • Slight learning curve • Debugging async flows can get tricky • Not always necessary for simple use cases 🔹 What actually matters It’s not about which one is better - it’s about your use case: • For most simple services I’ve worked on ➡️ RestTemplate was enough • For higher throughput or async needs ➡️ WebClient makes more sense ♣️ One thing I’ve realized: Using WebClient everywhere doesn’t automatically improve performance. Sometimes, improving timeouts or fixing DB queries had more impact than changing the client. Understanding where your real bottleneck is matters more. What are you using in your projects? Have you switched from RestTemplate to WebClient? #SpringBoot #Java #Microservices #BackendDevelopment #SystemDesign

Most developers treat HTTP status codes as just numbers… 👉 But they’re actually communication signals from your backend. Let’s simplify it 👇 🔹 What are HTTP Status Codes? They tell the client:👉 What happened with the request 🔹 1xx – Informational👉 Request received, still processing (Not used much in day-to-day apps) 🔹 2xx – Success ✔ 200 OK → Request successful✔ 201 Created → Resource created✔ 204 No Content → Success, no response body 🔹 4xx – Client Errors ❌ 400 Bad Request → Invalid input❌ 401 Unauthorized → Not logged in❌ 403 Forbidden → No permission❌ 404 Not Found → Resource doesn’t exist 🔹 5xx – Server Errors 💥 500 Internal Server Error → Something broke💥 502/503 → Service unavailable 🔹 Real Example: User tries to access profile 👇 • Not logged in → 401• Wrong ID → 404• Server crash → 500 👉 Same API, different outcomes 🔹 Common Mistake: ❌ Returning 200 for everything 👉 Makes debugging harder👉 Breaks frontend logic 🔹 Best Practice: 👉 Use status codes properly👉 Combine with meaningful error messages 💡 Big Insight: Good APIs don’t just return data… 👉 They return clear signals If you're building APIs… 👉 Are you using status codes correctly or just returning 200? #Backend #RESTAPI #HTTP #SystemDesign #Java #SpringBoot #Developers #TechGrowth

Most APIs function correctly, but very few are designed well Swipe to understand what good REST API design actually involves Early on, I approached APIs as simple CRUD implementations define endpoints, connect services, and move on Over time, it became clear that building scalable systems requires more than that This breakdown highlights key aspects that often get overlooked • Applying REST principles beyond basic implementation • Choosing the right HTTP methods based on intent • Structuring resources in a clear and consistent way • Using status codes and headers effectively • Considering authentication, caching, and rate limiting from the start The shift from writing endpoints to designing systems changes how backend development is approached What aspects of API design have been the most challenging in your experience #BackendDevelopment #Java #SpringBoot #RESTAPI #SoftwareEngineering #SystemDesign #JavaDeveloper

🚀 Understanding HTTP Status Codes (Every Developer Should Know) When working with APIs, debugging issues, or testing endpoints in Postman, HTTP status codes are your first clue to what’s happening behind the scenes. Let’s break it down in a simple way 👇 🔹 1xx – Informational Request received, continuing process (rarely used in day-to-day development) 🔹 2xx – Success ✅ ✔️ 200 OK → Request successful ✔️ 201 Created → Resource created (POST API) ✔️ 204 No Content → Success but no response body 🔹 3xx – Redirection 🔁 ✔️ 301 → Permanently moved ✔️ 302 → Temporary redirect 🔹 4xx – Client Errors ⚠️ (Your request has an issue) ❌ 400 Bad Request → Invalid data sent ❌ 401 Unauthorized → Missing/invalid authentication ❌ 403 Forbidden → No permission ❌ 404 Not Found → API or resource doesn’t exist 🔹 5xx – Server Errors 💥 (Server-side problem) ❌ 500 Internal Server Error → Something broke in backend ❌ 503 Service Unavailable → Server overloaded/down 💡 Pro Tip: Good APIs don’t just return status codes — they return meaningful error messages. Example: { "success": false, "message": "Invalid user ID", "statusCode": 400 } 📌 Why this matters: Understanding these codes helps you debug faster, build better APIs, and communicate clearly between frontend & backend. #WebDevelopment #API #Backend #NodeJS #MERN #Postman #SoftwareDevelopment #Coding

🚀 New beginnings, new systems, and exciting challenges ahead. Recently started working on a new backend ecosystem and got the opportunity to build a foundational service enabling Search Bills functionality using Java Spring MVC While the feature sounds straightforward, the real focus was on designing it to fit seamlessly within a larger distributed system. 🔧 Key focus areas: - Designed REST APIs with a clean layered architecture (Controller → Service → Integration) - Built a client abstraction layer to integrate with downstream ESS systems - Ensured the solution is scalable, maintainable, and extensible for future enhancements - Established a strong backend foundation aligned with enterprise integration patterns 💡 In enterprise environments, it’s not just about building APIs — it’s about how well they integrate, scale, and evolve with the system. Looking forward to contributing more towards building reliable and scalable backend systems. #Java #SpringMVC #Microservices #BackendEngineering #SystemDesign #NewBeginnings

-> Not all failures are permanent. Some just need a second chance. In real systems, failures happen due to: • Network issues • Temporary service downtime • Timeout errors But many APIs fail immediately. --- ❌ Without Retry Your Service ↓ External API (temporary failure) ↓ Request Failed ❌ Even if the issue is temporary. --- ✅ With Retry Your Service ↓ Retry (3 attempts) ↓ External API ↓ Success ✅ Now: ✔ Handles temporary failures ✔ Improves success rate ✔ Better user experience --- ⚙️ Spring Boot Example (Resilience4j) @Retry(name = "paymentService") public String callPayment() { return paymentClient.call(); } --- 🧠 Best Practices • Limit retry attempts (2–3 max) • Add delay between retries • Combine with timeout • Avoid retry for critical failures --- ⚠️ Important Retry blindly = system overload. Use it smartly. --- 💡 Lesson Don’t fail fast always. Retry smart… then fail. --- becoming production-ready with Spring Boot. Question: Do you use retry in your APIs? --- #Java #SpringBoot #BackendEngineering #Microservices #Resilience