Learned about @Async in Spring Boot: proxy requirement for parallel execution

Today I learned something interesting about Spring Boot’s @Async annotation. I was debugging why an async method wasn’t actually running in parallel — and eventually realized it was because I was calling it from within the same class. Since the call never went through the Spring proxy, the @Async behavior didn’t trigger. Lesson: @Async only works when the method is invoked through a Spring-managed proxy — not via direct internal calls within the same bean. Moving the method to a separate service (or injecting the bean itself via a proxy) fixed it instantly. A small reminder that many “magic” framework features are really just smart proxies under the hood — and understanding how they work can save hours of debugging. Have you ever run into similar proxy or async surprises in Spring Boot? #TodayILearned #SpringBoot #Java #Microservices #BackendDevelopment #LearningInPublic

🚀 Debugging @Async in Spring Boot Was wondering why my async method wasn’t actually running in parallel… After some digging, I realized the issue: 👉 I was calling it from the same class, so Spring’s proxy never intercepted the method call. 💡 Lesson learned: @Async (just like @Transactional) only works when the method is invoked through the Spring proxy, not directly within the same bean. ✅ Moving the method to a separate service (or injecting the bean into itself via proxy) instantly fixed it. It’s a good reminder — many Spring features are just smart proxies under the hood. Understanding that saves hours of debugging! Have you ever hit similar proxy or async issues in Spring Boot? #TodayILearned #SpringBoot #Java #Microservices #BackendDevelopment #AsyncProgramming #SpringFramework #LearningInPublic #JavaDevelopers #TechTips #CodeBetter

Before the release of Spring Boot 4, it was necessary to explicitly include the following dependency for JSON serialization and deserialization: <dependency> <groupId>com.fasterxml.jackson.dataformat</groupId> <artifactId>jackson-dataformat-xml</artifactId> </dependency> However, starting with Spring Boot 4.0.x, this functionality is included with the spring-boot-starter-webmvc artifact or dependency as a tool with dependency as a spring-boot-starter-jackson, and the import changes accordingly, exhibiting a transitive nature. For more details about Jackson 3 support in Spring Boot 4, please read through https://lnkd.in/gvGN58M7 Spring I/O #springboot4 #springframework #java

@Component vs @Bean @Component marks a class for automatic bean detection via scanning. @Bean defines a bean manually inside a @Configuration class. Use @Component for simple POJOs and services. Use @Bean when you need full control over object creation. Both ultimately register beans in the Spring container. #SpringFramework #Java #SoftwareEngineering #BackendDevelopment

🧩 Spring Boot Tip: Simplify Dependency Injection with @Autowired Constructor! Want cleaner beans and easier testing? Use constructor injection with Spring’s @Autowired on constructors—making your dependencies explicit and your classes immutable. ✨ Example: @Service public class UserService { private final UserRepository userRepository; @Autowired public UserService(UserRepository userRepository) { this.userRepository = userRepository; } } Benefits: Easier unit testing, mandatory dependency injection, and clearer design. 💡 Pro Tip: Starting from Spring 4.3, @Autowired on constructors is optional if the class has a single constructor. How do you prefer to inject dependencies in your Spring apps? Share your favorite DI style! #SpringBoot #Java #DependencyInjection #Autowired #CleanCode #BackendTips #DesignPatterns

⚙️ Bean Lifecycle in Spring Every Spring bean goes through stages like instantiation, dependency injection, initialization, and destruction. Developers can customize these steps using lifecycle annotations such as @PostConstruct and @PreDestroy. Spring automatically manages this entire lifecycle, ensuring optimal resource handling and clean object management. 🔁 #SpringBoot #SpringFramework #Java #SpringBeans #Lifecycle #BackendDevelopment

Understanding HandlerInterceptor Order in Spring Boot When you register multiple HandlerInterceptors in a Spring Boot application, have you ever wondered which one runs first? Here’s how Spring decides the order: Unlike Filters (which use @Order), HandlerInterceptors run in the order they are registered inside your WebMvcConfigurer. #SpringBoot #Java #SoftwareEngineering #BackendDevelopment #SpringMVC #CleanArchitecture

𝐇𝐨𝐰 𝐈 𝐔𝐬𝐞 𝐟𝐢𝐧𝐚𝐥 I make use of final to mark 𝐯𝐚𝐫𝐢𝐚𝐛𝐥𝐞𝐬, 𝐩𝐚𝐫𝐚𝐦𝐞𝐭𝐞𝐫𝐬, and 𝐟𝐢𝐞𝐥𝐝𝐬 when they won’t change. It prevents    1. Accidental reassignments.    2. Makes code intent clear.    3. Helps the JVM optimize. 𝐋𝐞𝐬𝐬𝐨𝐧 𝐋𝐞𝐚𝐫𝐧𝐞𝐝: Adding final to variables you don’t reassign prevents bugs and improves readability. For example, 𝐟𝐢𝐧𝐚𝐥 𝐒𝐭𝐫𝐢𝐧𝐠 𝐧𝐚𝐦𝐞 = 𝐮𝐬𝐞𝐫.𝐠𝐞𝐭𝐍𝐚𝐦𝐞() signals it’s not meant to change. Use it in methods and loops — it’s free safety! #Java #SpringBoot #CleanCode

🔹 Spring Scopes in a Nutshell Session bean → Singleton dependency ✅ Each user gets their own session bean All share the same singleton Singleton → Session dependency ❌ Singleton can’t directly hold a session bean Spring injects a proxy (like a mailbox) When the singleton calls a method, the proxy delivers it to the correct session bean for the current user 💡 Analogy: Session → Singleton: each user has their notebook, everyone uses the same pen ✍️ Singleton → Session: singleton talks to a mailbox, which routes messages to the right notebook 📬 Mix scopes carefully — proxies make it safe! #SpringBoot #Java #SessionScope #Singleton #BackendEngineering #SpringTips