Spring Boot Project Setup and Basics

🚀 What really happens when you run a Spring Boot application? Most developers use: 👉 SpringApplication.run(App.class, args); …but few understand what happens behind the scenes. Here’s a clear breakdown: 🔹 1. Bootstrapping Starts The JVM calls main(), and Spring Boot begins initialization. 🔹 2. Environment Setup Loads application.properties / application.yml, environment variables, and profiles. 🔹 3. ApplicationContext Creation Spring creates the IoC container to manage all beans. 🔹 4. Component Scanning Detects @Component, @Service, @Repository, @RestController and registers them. 🔹 5. Auto-Configuration Based on dependencies, Spring Boot configures components automatically (MVC, JPA, etc.). 🔹 6. Embedded Server Startup Starts embedded Apache Tomcat—no external installation needed. 🔹 7. DispatcherServlet Initialization Registers the front controller to handle all incoming HTTP requests. 🔹 8. Bean Initialization & Dependency Injection All beans are created and wired using DI. 🔹 9. Application Ready ✅ Your app is now ready to handle requests. 💡 Key Takeaway: SpringApplication.run() is not just a method—it bootstraps the entire application, sets up the container, auto-configures components, and starts the web server. #Java #SpringBoot #BackendDevelopment #Microservices #Programming #SoftwareEngineering #TechLearning

Most people use Spring Boot. But very few understand what actually happens when the application starts While going deeper into it, a few things started making more sense How the application context is created What SpringBootApplication really triggers How the bean lifecycle actually works Why proxies are used for things like Transactional And how self invocation can silently break things It is easy to write Spring code Understanding what happens inside is different Still learning and connecting the dots What part of Spring feels confusing to you #Java #SpringBoot #BackendDevelopment #SoftwareEngineering #JavaDeveloper #SystemDesign #Placements

Spring Boot Bean Lifecycle — Most developers ignore this 🔥 Do you know what happens before your bean is ready? Here’s the flow 👇 1️⃣ Bean Instantiation 2️⃣ Dependency Injection 3️⃣ @PostConstruct runs 4️⃣ Bean is ready to use ✅ And before shutdown: 👉 @PreDestroy is called 💡 Why it matters: ✔ Resource initialization ✔ Cleanup logic ✔ Better control over application lifecycle ⚠️ Mistake: Putting heavy logic inside constructors ❌ 👉 Use @PostConstruct instead Understanding lifecycle = writing smarter Spring Boot apps 🚀 #SpringBoot #Java #BackendDeveloper

🧠 My Spring Boot API just became more production-ready today 👀 I implemented Global Exception Handling 🚀 Before this 👇 ❌ Errors returned messy stack traces ❌ No clear message for users Now 👇 ✅ Clean JSON error responses ✅ Proper HTTP status codes ✅ Centralized error handling Example 👇 { "message": "User not found", "status": 404 } 💡 My takeaway: Handling errors properly is what separates a basic API from a production-ready backend ⚡ #Java #SpringBoot #ExceptionHandling #BackendDevelopment #LearningInPublic

🚀 Day 20/100: Spring Boot From Zero to Production Topic: Custom Auto-Configuration We covered Auto-Configuration. We covered disabling it. But does it stop there? Nope. 👀 Spring Boot lets you build your own auto-configuration too. 🔧 But, How It Works? You create a @Configuration class and slap conditionals on it. Spring Boot only loads it if your conditions are met. Two most common ones: @ConditionalOnClass → Load only if a class exists on the classpath @ConditionalOnProperty → Load only if a property is set in application.properties 💡 See the code attached below. ⬇️ No DataSource on classpath? → Skipped entirely db.enabled=false? → Skipped entirely Bean already defined by user? → Your default is skipped ✅ 📌 Don't forget to register it In META-INF/spring/org.springframework.boot.autoconfigure.AutoConfiguration.imports: -> com.yourpackage.MyDataAutoConfiguration Without this, Spring Boot won't pick it up. Checkout the previous posts on Auto-Config & disabling it to better understand the sequence. See you in the next one! #Java #SpringBoot #SoftwareDevelopment #100DaysOfCode #Backend #AutoConfiguration

Last week, I was debugging a strange issue in my Spring Boot application.Everything worked fine locally… but suddenly started breaking in production. After hours of digging, the culprit wasn’t my code. It was a transitive dependency. What is a Transitive Dependency? In a Maven-based Spring Boot project, you add a dependency like this: <dependency> <groupId>org.springframework.boot </groupId> <artifactId>spring-boot-starter-web </artifactId> </dependency> Looks simple, right? But behind the scenes, this pulls in many other dependencies automatically (like Jackson, Tomcat, etc.). These indirect dependencies are called transitive dependencies. The Problem: In my case, two different libraries were pulling different versions of the same dependency. Result? 1. Runtime conflicts 2. Unexpected errors 3. Debugging nightmare How I Fixed It: Step 1: Identify the dependency tree mvn dependency:tree Step 2: Find conflicting versions Step 3: Exclude unwanted dependency <dependency> <artifactId>koi</artifactId> <exclusions> <exclusion> <groupId>congflict</groupId> <artifactId>conflicting.any</groupId> </exclusion> </exclusions> <dependency> Step 4: Add the correct version explicitly Use: 1. mvn dependency:tree 2. mvn dependency:analyze These commands can save hours of debugging. Key Takeaway: Transitive dependencies are powerful…but if ignored, they can silently break your application. Always know what comes along with what you import. #Java #SpringBoot #Maven #BackendDevelopment #Debugging #SoftwareEngine

Most developers use Spring Boot… but don’t understand how it actually works. Here’s a simple breakdown 👇 When you run a Spring Boot application: 1️⃣ SpringApplication.run() is triggered 2️⃣ It creates an Application Context 3️⃣ Auto-configuration kicks in 4️⃣ Beans are created & injected (IoC container) 5️⃣ Embedded server (Tomcat) starts 6️⃣ Your APIs are ready 🚀 💡 The magic is in Auto Configuration Spring Boot scans dependencies & configures things automatically. 👉 Example: Add spring-boot-starter-web → you get Tomcat + DispatcherServlet + MVC setup. ⚠️ Mistake developers make: Using Spring Boot without understanding what's happening under the hood. If you understand this flow → debugging becomes EASY. Follow me for backend engineering insights 🚀 #Java #SpringBoot #BackendDeveloper #Microservices

Monday insight: Spring Boot 4.1.0-M3 adds refined observability attributes, making metrics and testing even smoother in backend pipelines. Milestone: https://lnkd.in/g5D8_9mS From framework familiarity, these simplify production monitoring. Following the 4.1 milestones? What excites you? #SpringBoot #Java #Observability #Testing #TechMilestones

Monday insight: Spring Boot 4.1.0-M3 adds refined observability attributes, making metrics and testing even smoother in backend pipelines. Milestone: https://lnkd.in/g5D8_9mS From framework familiarity, these simplify production monitoring. Following the 4.1 milestones? What excites you? #SpringBoot #Java #Observability #Testing #TechMilestones

⚔️ Spring vs Spring Boot Spring Framework 🔹 Requires manual configuration 🔹 More control and flexibility 🔹 Takes more setup time Spring Boot 🔹 Auto-configuration (less setup) 🔹 Embedded server (no need to deploy separately) 🔹 Faster development 💡 In short: Spring Boot is built on top of Spring to make development quicker and easier. 👉 Use Spring Boot for rapid development 👉 Use Spring when you need full control #Java #SpringFramework #SpringBoot #BackendDevelopment #Coding