Spring Boot Bean Lifecycle Explained

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

🚀 Mastering Spring Boot – Step by Step (Day 2) Still using "new" in Spring? ❌ 👉 Then you’re missing the core idea of Spring 💡 What is a Spring Bean? A Bean is: 👉 Any object managed by the Spring IoC container Instead of: UserService service = new UserService(); Spring does: ✔ Create objects ✔ Manage lifecycle ✔ Connect components 💡 What is IoC (Inversion of Control)? 👉 You don’t control object creation anymore 👉 Spring does it for you This leads to: ✔ Cleaner code ✔ Loose coupling ✔ Better scalability 💡 Simple way to think: You: "I will create objects" ❌ Spring: "I will handle everything" ✅ 👉 This is the foundation of Spring Next → Dependency Injection (real magic begins) 🔥 #Spring #SpringBoot #Java #Backend #LearningInPublic

🧠 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

💡 What is a REST API? (Simple explanation) As I’m learning Spring Boot, I’ve been working a lot with APIs. Here’s how I understand it: A REST API is basically how different applications talk to each other. Example: When you open an app and see data → it usually comes from an API. You send a request → server responds with data. That’s it. Simple nerh… but powerful. #SoftwareDevelopment #BackendDevelopment #Java #SpringBoot

@Value vs @ConfigurationProperties in Spring Boot 🤔 Most developers only use @Value… but that’s not scalable ❌ Let’s compare 👇 ✅ @Value - Good for small values - Not ideal for complex configs ✅ @ConfigurationProperties - Maps entire config to POJO - Clean & maintainable Example: @ConfigurationProperties(prefix = "app") public class AppConfig { private String name; private String version; } 💡 Why it matters: ✔ Cleaner code ✔ Better structure ✔ Easy to manage configs 👉 For real projects → always prefer @ConfigurationProperties Small improvement → big impact 🔥 #SpringBoot #Java #Configuration

🧠 After learning Dependency Injection, I had one big question 👀 Who actually creates these objects in Spring Boot, and when? Today I explored the Spring Bean Lifecycle 🚀 Simple flow 👇 1️⃣ Spring container starts 2️⃣ Bean object is created 3️⃣ Dependencies are injected 4️⃣ Bean becomes ready to use 5️⃣ Bean is destroyed when the app shuts down What made this even more interesting 👇 ✅ @PostConstruct → runs after bean creation ✅ @PreDestroy → runs before bean cleanup 💡 My takeaway: Spring doesn’t just inject dependencies — it also manages the entire lifecycle of the object. The more I learn this framework, the more beautifully engineered it feels ⚡ #Java #SpringBoot #BeanLifecycle #BackendDevelopment #LearningInPublic

🚀 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

⚙️ One Spring Boot Practice That Changed My Code Quality I stopped using field injection. ❌ @Autowired on fields ✅ Constructor Injection Why? ✔ Better testability ✔ Immutable dependencies ✔ Cleaner design Small change… big impact. If you’re still using field injection — try this once. What’s your preferred approach? 🤔 #SpringBoot #Java #BestPractices

💡 3 things I wish I knew before my first production deployment: → Caching is not optional at scale — it's survival → A 30% query optimization can feel like buying new hardware → Logs are your best friend at 2AM when things break Backend development taught me that performance is a feature, not an afterthought. #Java #SpringBoot #BackendEngineering #LessonsLearned

📘 Spring Notes – 4 Understanding Dependency Injection is one thing… Implementing it is where the real learning happens 💻 Today I worked on: ✔️ Setter vs Constructor Injection ✔️ Autowiring ✔️ Spring Bean Configuration (XML) Also pushed my practice code to GitHub: 👉 https://lnkd.in/gN-j5n3V Slowly building strong backend fundamentals 🚀 Follow for daily updates on my Spring journey. #Java #SpringBoot #Backend #Developers #Learning #TechJourney