Spring Framework Bootstrapping and Dependency Injection Flow

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

What’s your go-to approach for dynamic search in Spring Boot? 🤔 When it comes to JPA Specifications vs @Query most developers get this decision wrong. ❌ Here’s how to actually choose the right one 👇 #SpringBoot #Java #SoftwareEngineering

🚀 Day 8 — Spring Bean Lifecycle (Complete Flow 🔥) Today I learned how Spring creates, manages, and destroys objects (Beans) 👇 💡 Bean Lifecycle (Simple Flow): 👉 Create Bean 👉 Inject Dependencies 👉 Initialize Bean 👉 Use Bean 👉 Destroy Bean ⚡ Important Annotations: @PostConstruct → runs after bean creation @PreDestroy → runs before bean destruction 🔍 What Spring does internally? 👉 IoC Container: Creates object Injects dependencies Manages lifecycle 💡 One simple line: 👉 Spring controls the entire life of an object 💬 Did you know Spring handles object destruction too? Day 8 done ✅ #Spring #Java #BackendDevelopment #LearningInPublic #30DaysOfCode #SpringBoot #Developers

#java #springboot #tips 🚫 Stop using field injection in Spring Boot. Here’s why: Most developers write this: @Autowired private UserService userService; ✅ Use constructor injection instead: @Service @RequiredArgsConstructor public class OrderService { private final UserService userService; // immutable + testable } Why it matters: • Fields are final → truly immutable • Easier to unit test without Spring context • Fails fast at startup if bean is missing • Works perfectly with Lombok’s @RequiredArgsConstructor This is also the official Spring recommendation since Spring 4.x. #Java #SpringBoot #CleanCode #BackendDev

https://lnkd.in/d2QuDRvF Most “exciting” releases break your code. #Java26 doesn’t. It compiles, runs, and improves performance—thanks to G1 GC and HTTP/3. Lutske de Leeuw & Johannes Bechberger explain why boring wins. See why boring tech is a competitive advantage. Read their article! #Java #JVM

⚠️ Why @Transactional Sometimes Doesn’t Work in Spring Boot A common mistake: Calling a @Transactional method   from another method inside the SAME class. Result? Transaction doesn’t trigger. Why? Because Spring uses proxies. Internal method calls bypass the proxy,   so transaction management never happens. Fix: → Move logic to another service   OR   → Call through Spring-managed bean Small detail. Big production issue. #springboot #java #backendengineering

Spring Boot HandlerExceptionResolver — Advanced error handling 🔥 Most devs use @ControllerAdvice… but there’s a deeper layer 👇 👉 HandlerExceptionResolver It gives full control over: ✔ Exception handling ✔ HTTP response ✔ Error mapping 💡 Why use it? ✔ Fine-grained control ✔ Custom framework-level handling ⚠️ Use case: When @ExceptionHandler is not enough 👉 Example: Handle all exceptions globally with custom logic This is how frameworks are built internally 💯 #SpringBoot #Java #ExceptionHandling

Fixing a Real Spring Boot Error (and what it taught me) While building a simple REST API, I encountered this error:  ClassCastException: Product cannot be cast to Prodcut 🔍 What went wrong? I unknowingly created two different classes: Product ✅ (correct model) Prodcut ❌ (typo) Then I tried to cast one into another — which caused the application to crash. Why this error happens In Java, even a small typo creates a completely new class.So: Product ≠ Prodcut Java treats them as entirely different types, and casting between them is not allowed. #Java #SpringBoot #Debugging #BackendDevelopment #CodingJourney #SoftwareEngineering

Hot take 🔥 Most developers focus too much on: ❌ Learning new frameworks ❌ Memorizing syntax And too little on: ✅ System design ✅ Debugging skills ✅ Writing clean, maintainable code Frameworks change. Strong fundamentals don’t. Agree or disagree? 👇 #SoftwareEngineering #CleanCode #Java #FullStackDevelopment

I had an API that was “working fine”. But under load, response time spiked. Turned out I was fetching full entities when I only needed 3 fields. Switched to DTO projection. Same logic, much faster response. Lesson: don’t fetch what you don’t need. #Backend #SpringBoot #Performance #Java