Understanding Spring Beans in 7 Days

🚀 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

Spring Boot Custom Argument Resolver 🚀 Want to inject custom objects into controller automatically? You can 👇 public class UserArgumentResolver implements HandlerMethodArgumentResolver { @Override public boolean supportsParameter(MethodParameter parameter) { return parameter.getParameterType().equals(User.class); } @Override public Object resolveArgument(...) { return getUserFromToken(); } } 💡 Use case: ✔ Extract user from JWT ✔ Avoid repeated code in controllers 👉 Clean & powerful approach 🔥 Real-world: Used in production for authentication context This is advanced Spring Boot design 💯 #SpringBoot #Java #Backend

I just finished the book Java Web Internals. As someone still growing in the Java ecosystem, I’ve often felt like frameworks like Spring or Tomcat were a bit of a "black box." This book completely changed that for me. It’s well-written and focuses on building things from scratch rather than just following recipes. My biggest takeaways: Building from the ground up: Starting with low-level socket programming to build a multithreaded server made the "magic" of web requests finally click. Under the hood: Implementing reflection, annotations, and dependency injection manually gave me a whole new perspective on how modern frameworks actually work. Practical Design: It moves perfectly from basic networking to creating a custom framework, making complex system design feel approachable. If you’ve built a few projects but want to truly understand the "why" behind the tools we use every day, this is a must-read. I cannot thank Packt Vinishka Kalra for sharing the book. Thanks #Java #WebDevelopment #SoftwareEngineering #LearningToCode #SystemDesign #JavaDeveloper

#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

Built an HTTP server from scratch in Java. No frameworks. No Netty. No Spring Boot. Just raw sockets, manual byte parsing, and a thread pool wired from the ground up. The goal was never to reinvent the wheel. It was to understand what the wheel is actually made of. What was built: → TCP socket listener handing connections to a fixed thread pool of 500 workers → HTTP/1.1 parser written byte-by-byte - request line, headers, body (JSON + form-urlencoded) → Router handling HEAD, GET and POST with static file serving and query param injection → Structured error responses for 400, 404, 500, 501, and 505 → WebRootHandler with path traversal protection → Full JUnit test suite, Maven build, SLF4J logging, and a Dockerized deployment What it reinforced: Networking - HTTP is just bytes on a wire. The kernel speaks TCP, not HTTP. The parser is what gives those bytes meaning. Operating systems - the boundary between user space and kernel space stopped being abstract. accept(), read(), write() are syscalls. Everything else lives in the JVM. Concurrency - 500 threads sharing a single handler. Statelessness stops being a design preference and becomes a correctness requirement. Docker - the container wraps the JVM, not the kernel. Syscalls go to the host kernel. There is no container kernel. Building something from scratch is one of the most honest ways to learn. Every assumption gets tested, every abstraction gets earned. A recommendation from Kashif Sohail turned into weeks of going deep on networking, OS internals, and concurrency. Grateful for that push. GitHub repo :https://lnkd.in/dxxjXxpt #Java #Networking #OperatingSystems #Backend #SystemsEngineering #Docker #OpenSource

🚀 Spring Boot Tip: @Qualifier vs @Primary (Fix Bean Ambiguity) Facing this error? 👇 "NoUniqueBeanDefinitionException" 👉 It means Spring found multiple beans of the same type and doesn’t know which one to inject. --- ✅ @Qualifier — Be Explicit Use "@Qualifier" when you want to specifically choose a bean. @Autowired @Qualifier("upiPaymentService") private PaymentService paymentService; ✔ You tell Spring exactly which implementation to inject ✔ Best when you have multiple beans and need control --- ✅ @Primary — Set a Default Use "@Primary" to mark one bean as the default choice. @Component @Primary class CreditCardPaymentService implements PaymentService {} ✔ Spring will pick this automatically ✔ Works when no "@Qualifier" is specified --- 🧠 Key Difference 👉 "@Qualifier" = Explicit selection 👉 "@Primary" = Default fallback --- ✨ Pro Tip If both are present: ➡️ "@Qualifier" overrides "@Primary" --- #SpringBoot #Java #BackendDevelopment #CodingTips #SoftwareEngineering

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

🌱 Behind every powerful Spring Boot application lies a strong foundation — the Spring Core Frameworks. Most developers jump directly into Spring Boot, but understanding the core modules gives you a real edge in backend development. 🔹 Spring Core – IoC & Dependency Injection🔹 Spring Beans – Object lifecycle management🔹 Spring AOP – Logging, security, transactions🔹 Spring Context – Application configuration & events🔹 SpEL – Dynamic expressions & querying🔹 Spring Instrumentation – Class loading & monitoring Mastering these concepts helps you write cleaner code, build scalable systems, and crack interviews with confidence 🚀Strong applications are built on strong foundations. Which Spring module helped you the most in your journey? 👇 .... .... .... #SpringFramework #SpringBoot #Java #BackendDevelopment #SoftwareEngineering #Developers #Programming #TechLearning #JavaDeveloper #CodingJourney #Microservices #SystemDesign #LearnJava #SpringCore #TechCareer

🚀 Day 6 of Advance Java Today’s class was focused on understanding one of the most important concepts in Java Web Development — Servlets. What I learned today: ✅ What a Servlet is ✅ Why Servlets are used in web applications ✅ How a Servlet works inside a web container/server ✅ The Servlet Life Cycle ✅ The role of these important methods: init() service() destroy() Key Understanding from today’s session: A Servlet is a Java program that runs on the server side and handles client requests. What I found most interesting was learning how the Servlet Container manages the complete life cycle of a servlet: Servlet Life Cycle Flow: 1. Loading & Instantiation The server loads the servlet class and creates its object. 2. Initialization – init() This method is called only once when the servlet is initialized. 3. Request Processing – service() This method handles every incoming client request. 4. Destruction – destroy() Called before removing the servlet from memory. Today’s takeaway: Before learning frameworks like Spring, understanding how request handling actually works internally is very important — and Servlets are the foundation for that. Slowly building the backend basics step by step. 💻☕ Thanks to Anand Kumar Buddarapu Sir Saketh Kallepu Sir Uppugundla Sairam Sir #Codegnan #AdvanceJava #Java #Servlet #JavaWebDevelopment #BackendDevelopment #JDBC #JavaDeveloper #LearningJourney #StudentDeveloper #Programming #TechJourney #JavaFullStack