Global Exception Handling in Spring Boot with @ControllerAdvice

🚀 Day 18/100: Spring Boot From Zero to Production Topic: Auto-Configuration 💡 What is Auto-Configuration? One of the most powerful features in Spring Boot Turns hours of setup into minutes Eliminates heavy XML configs and manual bean wiring ⏳ Before Auto-Configuration Manually define multiple beans Write hundreds of lines of XML Configure everything yourself → painful ⚙️ What Happens Now? Your @SpringBootApplication kicks things off Spring Boot scans the classpath Looks for dependencies like: spring-webmvc spring-data-jpa 👉 Presence/absence of JARs = signals 🧠 Behind the Scenes Reads a special file: META-INF/spring/org.springframework.boot.autoconfigure.AutoConfiguration.imports Contains hundreds of auto-config classes Each uses conditions like: @ConditionalOnClass @ConditionalOnMissingBean 👉 Result: Beans get configured automatically 🌐 Simple Example Add: spring-boot-starter-web Spring Boot assumes: You need a web app So it adds an embedded server (Tomcat) automatically 🛠️ Can You Override It? YES You can: Define your own beans Override defaults Disable auto-config if needed Auto-configuration isn’t magic. It’s just smart defaults + conditional logic working for you #Java #SpringBoot #SoftwareDevelopment #100DaysOfCode #Backend

Most backend APIs are badly designed… and routing is usually the reason. I used to think routing was just: “URL → function” But it’s much deeper than that. Here’s what I learned 👇 • Method = what you want to do (GET, POST…) • Route = where you want to do it (/users, /books) • Together → form a unique key that decides backend behavior Types of routing that actually matter: • Static → fixed endpoints • Dynamic → /users/:id • Query params → filtering, pagination • Nested routes → relationships between resources • Versioning → avoid breaking production APIs • Catch-all → clean error handling 💡 Biggest realization: 👉 Good routing = clean APIs = scalable systems Bad routing = messy logic + hard-to-maintain backend I’ve put together clean notes in a PDF 👇 #BackendEngineering #SystemDesign #APIDesign #Java #SpringBoot

🚀 Day 19/100: Spring Boot From Zero to Production Topic: Disabling Auto Configuration Quick Recap previously we covered Auto Configuration in Spring Boot. (Link to that post in the comments 👇) The Problem: Auto Configuration is magical. But magic shouldn't cage you. Sometimes you need to go beyond the defaults. Sometimes a specific auto config just gets in your way. So the question is.... does Spring Boot let you opt out? Absolutely. And it's dead simple. ✅ How to Disable Auto Configuration: Just add an exclude to your @SpringBootApplication annotation: @SpringBootApplication(exclude = DataSourceAutoConfiguration.class) public class MunasibApplication{ public static void main(String[] args) { SpringApplication.run(MyApp.class, args); } } That's it. One line. No database auto-wiring. Done. Not Just DataSource You're not limited to one config. Exclude multiple auto configurations at once Works with any AutoConfiguration class Spring Boot ships @SpringBootApplication(exclude = { DataSourceAutoConfiguration.class, SecurityAutoConfiguration.class }) Alternative: Use application.properties Don't want to touch your code? spring.autoconfigure.exclude=\org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration Same result. Zero code change. 🎯 Why This Matters Spring Boot gives you sensible defaults. But it never forces them on you. That's what makes it a great framework, not just smart, but flexible. #Java #SpringBoot #SoftwareDevelopment #100DaysOfCode #AutoConfiguration

🚀 Spring Framework 🌱 | Day 17 Exception Handling in Spring Boot (Real Project Approach) In many projects, I’ve seen controllers filled with try-catch blocks. It works… but it quickly becomes messy and hard to maintain. A better approach in Spring Boot is: 👉 Centralized Exception Handling using @ControllerAdvice 💡 It’s important to follow these best practices in real projects. 1️⃣ Create a Global Exception Handler - Use @ControllerAdvice - Handle all exceptions in one place 2️⃣ Define Custom Exceptions - Example: ResourceNotFoundException, BusinessException - Helps in better clarity instead of generic Exception 3️⃣ Standard API Error Response Instead of random messages, always return structured response: { "timestamp": "...", "status": 404, "error": "Not Found", "message": "User not found", "path": "/users/10" } 4️⃣ Map Exceptions Properly - 400 → Bad Request (validation issues) - 404 → Resource not found - 500 → Unexpected errors 5️⃣ Avoid exposing internal details - Never return stack trace in API response (security risk) 🔥 Why this matters? ✔ Cleaner Controllers (no repetitive try-catch) ✔ Consistent API responses ✔ Easy debugging & logging ✔ Production-ready design ⚡ Pro Tip: Combine @ControllerAdvice with proper logging (SLF4J) and monitoring tools for better debugging in production. #SpringBoot #Java #BackendDevelopment #CleanCode #Microservices #SoftwareEngineering

Stop labeling your Spring Beans randomly! 🛑 I see many projects where @Component, @Service, and @Repository are used interchangeably. They all register a Bean in the context, so they are the same, right? Not exactly. Using the right stereotype is about Communication and Semantics. 🔹 @Service: Clearly states: "This is where the business logic lives." It's your domain's heart. 🔹 @Repository: Signals: "I talk to the database." Spring provides an extra layer of magic here: it automatically translates platform-specific exceptions (like SQLException) into Data Access Exceptions. 🔹 @Component: The generic catch-all. Use it for utility classes or anything that doesn't fit the service/repository pattern. Tip: Using the correct label makes your code readable for the next dev. It tells a story about what each class is responsible for before they even read a single line of implementation. How strict is your team with stereotyping their Spring components? Let’s talk below! 👇 #Java #SpringBoot #SoftwareArchitecture #CleanCode #Backend #SpringFramework #CleanDesign

What actually happens when you hit a Spring Boot API? In my previous post, I explained how Spring Boot works internally. Now let’s go one level deeper 👇 What happens when a request hits your application? --- Let’s say you call: 👉 GET /users Here’s the flow behind the scenes: 1️⃣ Request hits embedded server (Tomcat) Spring Boot runs on an embedded server that receives the request. --- 2️⃣ DispatcherServlet takes control This is the core of Spring MVC. It acts like a traffic controller. --- 3️⃣ Handler Mapping DispatcherServlet finds the correct controller method for the request. --- 4️⃣ Controller Execution Your @RestController handles the request → Calls service layer → Fetches data from DB --- 5️⃣ Response conversion Spring converts the response into JSON using Jackson. --- 6️⃣ Response sent back Finally, the client receives the response. --- Why this matters? Understanding this flow helps in: ✔ Debugging production issues ✔ Writing better APIs ✔ Improving performance Spring Boot hides complexity… But knowing what’s inside makes you a better backend developer. More deep dives coming #Java #SpringBoot #BackendDevelopment #Microservices

As developers, we all say *“async = separate thread”*… but when I went deeper during development, a few real questions hit me 👇 Can I actually **see which thread is running my async task?** Yes — using `Thread.currentThread().getName()` you can log and observe it. But then the bigger question… 👉 **How many threads are actually created?** 👉 Is it always a new thread per task? 👉 Or are threads reused? I came across a post saying **“by default 8 threads are used”** — but is that really true in all cases? From what I understand so far: * It depends on the **thread pool configuration** * Frameworks like Spring Boot often use executors (not raw thread creation) * Threads are usually **reused**, not created every time But I want to hear from real-world experience 👇 💬 How does async actually behave in production systems? 💬 What decides the number of threads? 💬 Any pitfalls you’ve seen while working with async? Let’s learn from each other 🚀

One thing I’ve learned building backend systems: Audit logging always starts as a “simple requirement” …and ends up being a complex subsystem. - Who changed what? - When did it happen? - Can we query it efficiently? Most teams either: 1. Over-engineer it 2. Or build something they regret later So I decided to build it properly once. Introducing nerv-audit (now on Maven Central): A Spring Boot audit framework powered by Hibernate Envers, with: - Clean architecture - Queryable audit history - Production-ready design If you're building serious systems, this is something you’ll eventually need. Full write-up here: https://lnkd.in/g2sv9dsM Curious how others are handling audit trails in their systems 👇 #SpringBoot #Java #SoftwareEngineering #Backend #OpenSource

#Post6 In the previous posts, we built basic REST APIs step by step. But what happens when something goes wrong? 🤔 Example: User not found Invalid input Server error 👉 By default, Spring Boot returns a generic error response. But in real applications, we need proper and meaningful error handling. That’s where Exception Handling comes in 🔥 Instead of handling exceptions in every method, Spring provides a better approach using @ControllerAdvice 👉 It allows us to handle exceptions globally Example: @ControllerAdvice public class GlobalExceptionHandler { @ExceptionHandler(Exception.class) public String handleException(Exception ex) { return ex.getMessage(); } } 💡 Why use this? • Centralized error handling • Cleaner controller code • Better API response Key takeaway: Use global exception handling to manage errors in a clean and scalable way 🚀 In the next post, we will create custom exceptions for better control 🔥 #Java #SpringBoot #BackendDevelopment #RESTAPI #LearnInPublic

Spring Boot Magic ✨ — Pagination Fetching thousands of records in one API call? That’s a performance nightmare waiting to happen 😅 👉 That’s where Pagination comes in. Pagination helps you load data in small chunks (pages) instead of everything at once. 💡 Why it matters? ✔ Improves performance ✔ Reduces memory usage ✔ Faster APIs ✔ Better user experience ⚙️ How it works in Spring Boot? Use Pageable to request data Return Page<T> from repository/service Control page, size, and sorting easily Example: /api/users?page=0&size=10&sortBy=id That’s it… clean, scalable, and production-ready 🚀 If you're building APIs and not using pagination, you're putting unnecessary load on your system. #SpringBoot #Java #Pagination #BackendDevelopment #APIDesign #CleanCode