Markus Eisele’s Post

🚀 Internal Working of IOC (Inversion of Control) in Spring. Understanding how Spring manages your application behind the scenes 👇 📌 Step-by-Step Flow: 1️⃣ Configuration Loading → Spring reads config (@Component, @Bean, etc.) 2️⃣ Bean Definition → Classes are identified & metadata is created 3️⃣ IOC Container → ApplicationContext initializes 4️⃣ Bean Creation → Objects created by Spring (no "new") 5️⃣ Dependency Injection → Dependencies injected (@Autowired) 6️⃣ Initialization → Init methods called (@PostConstruct) 7️⃣ Ready to Use → Bean is fully configured ✅ 8️⃣ Lifecycle Management → Create → Use → Destroy 9️⃣ Destruction → Cleanup (@PreDestroy) 💡 In Short: Spring handles object creation & dependencies, you focus only on business logic! ✨ IOC = Less effort, more control #Java #SpringBoot #SpringFramework #IOC #DependencyInjection #BackendDevelopment #Coding #InterviewPreparation

Nice material how to write efficient architecture (to handle many requests per seconds). It is always the same question we stand in front of Java and other platforms. https://lnkd.in/dm2_8XJX

🔒 Singleton Design Pattern — One Instance to Rule Them All Ever faced a situation where you need exactly one instance of a class throughout your application? That’s where the Singleton Design Pattern comes in. 💡 What is it? The Singleton pattern ensures that a class has only one instance and provides a global point of access to it. 🚀 Why use Singleton? Control shared resources (e.g., database connections, logging systems) Avoid unnecessary object creation Maintain a single source of truth 🧠 How it works: Make the constructor private Create a static instance of the class Provide a public method to access that instance 🧩 Simple Example (Java): public class Singleton { private static Singleton instance; private Singleton() {} public static Singleton getInstance() { if (instance == null) { instance = new Singleton(); } return instance; } } ⚠️ Things to watch out for: Thread safety issues in multithreaded environments Difficulties in unit testing Can lead to hidden dependencies if overused ✅ Pro Tip: Use Singleton only when truly needed. Overusing it can make your system rigid and harder to maintain. #DesignPatterns #SoftwareEngineering #Java #Programming #SystemDesign #Coding

🚀 Day 98/100 - Spring Boot - Creating & Listening to Custom Events As, we have discussed event-driven architecture in the previous post (https://lnkd.in/dWjTG_3j)... Now let’s implement it in Spring Boot. ➡️ Create and Listen to Custom Events it's a 3-step process: 🔹Step 1: Define a Custom Event 🔹Step 2: Publish the Event 🔹Step 3: Listen to the Event ❗See attached image for code 👇 ➡️ What’s Happening Actually? 🔹Event is published after user creation 🔹Listener automatically reacts 🔹No direct dependency between components #100Days #SpringBoot #EventDriven #Java #BackendDevelopment #SoftwareEngineering

Spring Boot Circular Dependency — Dangerous issue ⚠️ Example: Service A → depends on Service B Service B → depends on Service A 👉 Boom 💥 Circular dependency error 💡 Why it happens: Poor design & tight coupling Solutions 👇 ✅ Refactor logic ✅ Use constructor injection properly ✅ Introduce third service ✅ Use @Lazy (temporary fix) ⚠️ Avoid: Field injection (hard to debug) 👉 Best practice: Use constructor injection ALWAYS Clean architecture prevents these issues 🔥 #SpringBoot #Java #CleanCode

Devlog #6 - PulseNotify: Sometimes the best architectural decision is switching before you go too deep in the project. Today: - Switched from Thymeleaf to FreeMarker for lightweight, database driven template processing. - Built the TemplateController with a dedicated render endpoint - Used Java 21 Records with @Valid to ensure data integrity across the API - Achieved full coverage with JUnit 5 & Mockito, using @Spy to verify real FreeMarker processing. Check the commits here: https://lnkd.in/dPYf3m_D #Java #SpringBoot #Microservices #BuildingInPublic #SoftwareArchitecture

Have you ever debugged a production issue where logs show the same error everywhere… but you still can’t figure out what actually failed? I used to make this mistake a lot — catch exception → log error → throw again Service logs Repository logs Controller logs Same exception 3–4 times. Just noise. Then I changed one simple thing: don’t log where you’re just throwing the exception. Now I follow this: Service/Repository → just throw or wrap the exception Log only once at the boundary (API / consumer) Always add context We often don’t pay much attention to logging, but it plays a crucial role when debugging a system. You need clarity on where to log, what to log, and where not to. Now instead of messy logs, I get one clear error log with full context. Debugging feels less like guessing and more like tracing a story. Less logs. Better logs. That’s the real strategy. #BackendDevelopment #Microservices #SystemDesign #Java #SpringBoot #Logging #SoftwareEngineering #CleanCode

🚀How @Transactional works behind the scenes in Spring 🤔 I created this visual to break it down simply 👇 🔹 How @Transactional works behind the scenes 🔹 Proxy Design Pattern (JDK vs CGLIB) 🔹 AOP magic (Before → After → Exception) 🔹 Complete internal execution flow 🔹 Common mistakes (self-invocation, private methods, exceptions) 🔹 Propagation behaviors (REQUIRED, REQUIRES_NEW, NESTED, etc.) 🔹 Isolation levels (READ_COMMITTED → SERIALIZABLE) 💡 Key Takeaway: It’s not magic — Spring uses Proxy + AOP + Transaction Manager to manage transactions seamlessly. ⚠️ Real-world tip: If your transaction is not working, always check: ✔️ Is method called via proxy? ✔️ Correct propagation level? ✔️ Proper exception handling? #Java #SpringBoot #Transactional #AOP #BackendDevelopment #Microservices

#Day21 🧠 Multithreading Design Patterns — thinking beyond threads Multithreading isn’t just about creating threads — it’s about designing systems 💡 Some key patterns I explored today: 👉 Producer–Consumer → task queues 👉 Thread Pool → reuse threads 👉 CompletableFuture → async pipelines 👉 ThreadLocal → per-thread data 👉 Immutable objects → thread safety Example 👇 ExecutorService executor = Executors.newFixedThreadPool(3); executor.submit(() -> System.out.println("Task running")); 💡 Choosing the right pattern makes your system scalable and safe #Java #Multithreading #DesignPatterns #Concurrency #JavaDeveloper #SystemDesign #InterviewPreparation #LearningInPublic

🚀 Day 97/100 - Spring Boot - Event-Driven Communication with ApplicationEventPublisher In real world applications, not everything needs direct method calls... We often want loose coupling between components. That’s where Event Driven Communication comes in... ➡️ What is Event-Driven Approach? 🔹One component publishes an event 🔹Other components listen and react 🔹No tight dependency between them See attached image 👇 for architectural flow ➡️ Why Event Driven Architecture is Appreciated? 🔹It decouples components 🔹Improves scalability 🔹Provides cleaner architecture 🔹Easy to extend (you can add more listeners anytime) ➡️ How to create CustomEvents and listen to them? (will be covered in next post) Previous post - Configuration Server in Microserices: https://lnkd.in/dbvU7U7U #100Days #SpringBoot #EventDriven #Java #Microservices #BackendDevelopment #SoftwareEngineering