Spring Boot Environment Variable Issue with Underscores

Ever wondered how Spring Boot sets up a DataSource, EntityManagerFactory, and transactions — without you writing a single line of config? That's auto-configuration. And I just wrote my first blog post breaking down exactly how it works. What's covered: → The role of META-INF/spring/AutoConfiguration.imports → @ConditionalOnClass, @ConditionalOnMissingBean, @ConditionalOnProperty → How condition evaluation happens before any bean is created If you've ever typed @SpringBootApplication and moved on without questioning it — this one's for you. This is my first blog, so if I've missed anything or something could be explained better — feel free to drop a comment. Happy to discuss and improve! 🔗 Link in the comments! #SpringBoot #Java #Backend

🚀 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

🚨 Why I stopped using field injection in Spring Boot I used to write this: @Autowired private UserService userService; Looks clean… but caused real issues. ❌ Problems: * Hard to test * Hidden dependencies * NullPointer risks in edge cases ✅ Now I always use constructor injection: public UserController(UserService userService) { this.userService = userService; } 💥 Real benefit: While writing unit tests, I realized I could mock dependencies easily without Spring context. 💡 Takeaway: Field injection is convenient. Constructor injection is production-safe. Small change. Big impact. #Java #SpringBoot #BackendDevelopment #SoftwareEngineering  #Microservices #RESTAPI #SystemDesign  #DeveloperLife #100DaysOfCode

Spring Boot Filters vs Interceptors — Most developers confuse this 🤯 Let’s simplify 👇 ✅ Filter (Servlet level) - Works BEFORE DispatcherServlet - Used for logging, authentication, request modification ✅ Interceptor (Spring level) - Works AFTER DispatcherServlet - Used for business-level checks 💡 Flow: Request → Filter → DispatcherServlet → Interceptor → Controller ⚡ Real use case: - Filter → JWT validation - Interceptor → role-based access 👉 Choosing wrong = messy architecture Know the difference = cleaner backend 🔥 #SpringBoot #Java #BackendDeveloper

Spring Boot Bean Scope — Not just Singleton 🤯 Most developers only know this: 👉 Default scope = Singleton But there’s more 👇 ✅ Prototype → New instance every time ✅ Request → Per HTTP request ✅ Session → Per user session 💡 Why it matters: ✔ Memory optimization ✔ Better state handling ⚠️ Mistake: Using singleton for stateful data ❌ 👉 Leads to concurrency issues 🔥 Real lesson: Choose scope based on use case, not default Backend bugs often start here 🚨 #SpringBoot #Java #Architecture

🚨 Spring Boot Trap @Transactional looks simple. But it has rules. It works when: • Called from another bean • Public methods • Proxy is active It fails silently when: • Self-invocation • Wrong propagation • Async methods Result? Data inconsistency. Always test transaction boundaries. Don’t assume they work. #SpringBoot #Java #Transactions #Backend #BackendDevelopment #JavaDeveloper #SoftwareEngineering #TechTips #SoftwareEngineer

🚀 Day 20/100: Spring Boot From Zero to Production Topic: Custom Auto-Configuration We covered Auto-Configuration. We covered disabling it. But does it stop there? Nope. 👀 Spring Boot lets you build your own auto-configuration too. 🔧 But, How It Works? You create a @Configuration class and slap conditionals on it. Spring Boot only loads it if your conditions are met. Two most common ones: @ConditionalOnClass → Load only if a class exists on the classpath @ConditionalOnProperty → Load only if a property is set in application.properties 💡 See the code attached below. ⬇️ No DataSource on classpath? → Skipped entirely db.enabled=false? → Skipped entirely Bean already defined by user? → Your default is skipped ✅ 📌 Don't forget to register it In META-INF/spring/org.springframework.boot.autoconfigure.AutoConfiguration.imports: -> com.yourpackage.MyDataAutoConfiguration Without this, Spring Boot won't pick it up. Checkout the previous posts on Auto-Config & disabling it to better understand the sequence. See you in the next one! #Java #SpringBoot #SoftwareDevelopment #100DaysOfCode #Backend #AutoConfiguration

Most developers use threads in Spring Boot without ever needing to think about what is happening underneath. I did too until I realized that some performance issues are not caused by slow code, but by how the application is handling work internally. Understanding threads changed the way I think about background tasks, request handling, and scalability in Java applications. I wrote about how Spring Boot threads work, how to configure them properly, and when using them can improve or complicate your system. Read more here: https://lnkd.in/ePmp5rMa

🧠 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

Spring Boot Bean Lifecycle — Most developers ignore this 🔥 Do you know what happens before your bean is ready? Here’s the flow 👇 1️⃣ Bean Instantiation 2️⃣ Dependency Injection 3️⃣ @PostConstruct runs 4️⃣ Bean is ready to use ✅ And before shutdown: 👉 @PreDestroy is called 💡 Why it matters: ✔ Resource initialization ✔ Cleanup logic ✔ Better control over application lifecycle ⚠️ Mistake: Putting heavy logic inside constructors ❌ 👉 Use @PostConstruct instead Understanding lifecycle = writing smarter Spring Boot apps 🚀 #SpringBoot #Java #BackendDeveloper