Spring Boot Constructor Injection Simplified

🔥 DAY 2 **How Spring Boot Dependency Injection actually works (Simple explanation)** Most developers use @Autowired. Few understand what happens behind the scenes. Here’s what Spring does: • Scans components • Creates beans in ApplicationContext • Manages lifecycle • Injects dependencies via constructor/setter Why it matters? Because: * It improves testability * Reduces tight coupling * Makes large systems manageable Framework knowledge is good. Understanding internals is better. #SpringBoot #Java #BackendDevelopment

Hi everyone 👋 📌 Spring Boot Annotation Series Part 21 – @PathVariable @PathVariable is used to extract values from the URL path and bind them to method parameters. It is part of the Spring Framework and widely used in REST APIs built with Spring Boot. 🔹 Why Do We Use @PathVariable? In REST APIs, resources are identified using IDs in the URL. Example: GET /users/101 Here, 101 is part of the URL path. @PathVariable helps us capture that value inside the controller method. 🔹 Basic Example @RestController @RequestMapping("/users") public class UserController { @GetMapping("/{id}") public String getUserById(@PathVariable Long id) { return "User ID is: " + id; } } 👉 If request is: GET http://localhost:8080/users/101 Output: User ID is: 101 🔹 In Simple Words @PathVariable takes dynamic values from the URL and passes them to the controller method. #SpringBoot #Java #RESTAPI #PathVariable #BackendDevelopment #InterviewPreparation

TIL about Spring’s @ExceptionHandler selection rules — and it surprised me a bit. Quick summary: Inside the same @ControllerAdvice: root exception match > cause match Across different advice beans: @Order priority beats everything — even root vs cause. So a higher-priority advice matching a cause can override a lower-priority advice matching the actual exception. Lesson learned: Put your primary/global exception handlers in a high-priority @ControllerAdvice. Sharing in case it saves someone else a debugging session 🙂 #SpringBoot #Java

Collections in #Java Got to learn about List (ArrayList), Set (HashSet & TreeSet), Map (HashMap). I was introduced on how to iterate through each of the collection types, how Set does not allow for double entry and the unique identifier that Map offers using the "key". #java #backend #springboot

Have you ever wondered how Spring Boot injects dependencies ? “Spring injects dependencies automatically.” But very few can explain HOW. Here’s what really happens behind the scenes: 1- Spring scans your classes 2- It creates BeanDefinitions 3- The ApplicationContext instantiates beans 4- Dependencies are resolved via constructor/setter injection 5- Beans go through the full lifecycle (init → post-processors → ready) Dependency Injection is not magic. It’s a container managing object graphs for you. If you understand: • Bean lifecycle • Singleton vs prototype scope • BeanPostProcessor • ApplicationContext vs BeanFactory You’re already thinking beyond annotations. I just broke it all down step by step https://lnkd.in/ewNmUK5b #SpringBoot #SpringFramework #Java #BackendDevelopment #SoftwareArchitecture

Java 21+ Features Hack 🚀 Java devs, if you're still on Java 17 or earlier in 2026, you're missing game-changers from Java 21+! I just refactored a legacy Spring Boot microservice using Virtual Threads (Project Loom) and pattern matching in switch expressions — load times dropped 40%, and my code went from 200+ lines to under 100. Here's a quick breakdown: Virtual Threads: No more blocking I/O nightmares. Thread.ofVirtual().start(() -> { /* your async magic */ }); handles thousands of concurrent requests without thread pool exhaustion. Records + Pattern Matching: if (obj instanceof Point(int x, int y)) { return x + y; }—bye-bye verbose getters/setters! Sequenced Collections: List.of(1,2,3).getFirst() and getLast() for cleaner list ops. Pro tip: Pair this with Spring Boot 3.3 for auto-config magic. Who's experimenting with these? Drop your wins or gotchas below—I’m all ears! #Java21 #SpringBoot #BackendDev #java #knowledge #Features

💡 A Small Backend Concept That Clicked Recently Recently, I gained better clarity on why separation of concerns matters in backend services. Keeping controllers, services, and repositories focused on their own roles: • improves readability • makes changes safer • reduces mental overload Simple ideas, but powerful when applied consistently. #BackendDevelopment #Java #SpringBoot #CleanCode #LearningInPublic

Spring Boot dependency injection (DI) pitfalls I learned building my first REST API: Don't rely on field injection blindly-use constructors for immutability and testability. Scenario: Multiple beans of the same type? @Qualifier saves the day. @Autowired @Qualifier('taskServiceImpl') private TaskService taskService; Pro tip: @Configuration + @Bean for custom wiring. Deployed my task manager CRUD in 20 mins-zero null pointers. Reduced boilerplate by 60%. Try it on your next project! Thoughts? #SpringBoot #Java #BackendDev

Day 38 — LeetCode Progress (Java) Problem: Successful Pairs of Spells and Potions Required: For each spell, find how many potions form a successful pair such that spell × potion ≥ success. Idea: Sort the potions array so binary search can be used to find the first valid potion that satisfies the condition. Approach: Sort the potions array. For each spell, perform binary search on potions. Find the smallest index where spell × potion ≥ success. All potions to the right of that index form valid pairs. Store the count in the result array. Time Complexity: O(n log m) Space Complexity: O(1) (excluding output array) #LeetCode #DSA #Java #BinarySearch #Arrays #CodingJourney #100DaysOfCode