Spring Boot @RestController Explained

#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

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

Spring Boot @Bean vs @Component — Hidden difference 🔥 Both create beans… but NOT the same 👇 ✅ @Component - Auto-detected via component scan - Used for your own classes ✅ @Bean - Defined manually inside @Configuration - Used for third-party classes Example: @Bean public ObjectMapper objectMapper() { return new ObjectMapper(); } 💡 Why it matters: ✔ Better control over bean creation ✔ Custom configuration 👉 Use @Bean when you need flexibility Small concept → big design impact 💯 #SpringBoot #Java #Backend

Spring Boot @Conditional — Hidden superpower ⚡ You can load beans conditionally! Examples: ✅ @ConditionalOnProperty ✅ @ConditionalOnMissingBean ✅ @ConditionalOnClass 💡 Use case: Load bean ONLY when needed Example: @Configuration @ConditionalOnProperty(name="feature.enabled", havingValue="true") 👉 Feature toggles made easy 🔥 ✔ Better flexibility ✔ Environment control ✔ Cleaner configs Most developers don’t use this — big mistake ❌ #SpringBoot #Java #BackendDeveloper

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

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

💡 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

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

🚀 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

⚙️ 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