Spring Boot Circular Dependency Explained

🚀 Spring Boot Deep Dive: Solving the Singleton-Prototype Injection Problem Have you ever encountered a situation where your @Scope("prototype") bean behaves like a singleton when injected into a regular Spring service? 🧐 This is a classic challenge in Spring known as the "Scoped Bean Injection Problem." 🔍 The Problem A Singleton bean is instantiated only once by the Spring container. If you inject a Prototype bean into it using @Autowired, that injection happens only once at the time of the singleton's creation. The result? Every time you use that prototype bean inside your singleton, you are actually reusing the same instance instead of getting a fresh one. This defeats the entire purpose of the prototype scope! 🛠 The Solution: The @Lookup Annotation While there are several ways to fix this (like using ObjectFactory or implementing ApplicationContextAware), the most elegant and "Spring-way" is using the @Lookup annotation. 💻 How it works: * Create a method that returns the Prototype bean. * Annotate that method with @Lookup. * Spring will dynamically override this method to fetch a new instance from the container every time it is called. 📝 Code Example: @Component @Scope("prototype") class PrototypeBean { // New instance logic here } @Component class SingletonService { // Spring overrides this to return a new PrototypeBean every time @Lookup public PrototypeBean getPrototypeBean() { return null; } public void executeTask() { PrototypeBean freshInstance = getPrototypeBean(); System.out.println("Processing with: " + freshInstance); } } ✅ Why use @Lookup? * Decoupling: You don't need to manually interact with the ApplicationContext. * Readability: It clearly signals that the method's purpose is to provide a fresh dependency. * Thread Safety: Essential when the prototype bean is stateful and not thread-safe. Have you faced this issue in your production environment? How did you solve it—@Lookup, Provider<T>, or ObjectFactory? Let’s discuss in the comments! 👇 #SpringBoot #Java #SoftwareEngineering #BackendDevelopment #Microservices #CleanCode #SpringFramework #JavaDeveloper

A Spring Boot mistake that slows down your API. Using @Transactional on methods that don't need it. I've seen this pattern everywhere: @Transactional public User getUserById(Long id) { return userRepository.findById(id); } This is a read-only query. No updates. No writes. But @Transactional still opens a database connection, starts a transaction, and holds it until the method finishes. For simple reads, this adds unnecessary overhead. The fix is simple: @Transactional(readOnly = true) public User getUserById(Long id) { return userRepository.findById(id); } Or remove it entirely if you don't need transaction management. I optimized an API that had @Transactional on every method. Response time dropped by 25% just by cleaning this up. Small annotation. Big performance difference. What Spring Boot optimization gave you the best results? #SpringBoot #Java #Programming #BackendDevelopment #CodeReview

A Spring Boot mistake that breaks production but works in dev. Hardcoding environment-specific values. I've seen this pattern everywhere: String dbUrl = "localhost:5432/mydb"; String apiKey = "abc123"; Works fine on your machine. Breaks the moment it hits production. The fix is simple. Use externalized configuration. @Value("${database.url}") private String dbUrl; @Value("${api.key}") private String apiKey; Then set different values in application-dev.yml and application-prod.yml. I once spent 4 hours debugging a production issue. The root cause? A hardcoded URL that pointed to a dev server. One config change. Problem solved. Never hardcode what can change between environments. What's a config mistake that caught you off guard? #SpringBoot #Java #Programming #BackendDevelopment #CodeReview

🌱 My Spring Journey : Difference between BeanFactory and ApplicationContext BeanFactory Container : -> It can not pre-instantiate singleton scope spring bean -> It does not support to work with properties file -> It does not support for the Internationalization -> It does not support for Annotation driven configuration, 100% code driven configuration, spring boot application development ApplicationContext Container : -> It can pre-instantiate singleton scope spring bean -> It support to work with properties file -> It support for the Internationalization -> It support for Annotation driven configuration, 100% code driven configuration, spring boot application development -> But both containers support for the dependency injection, dependency lookup, autowiring, spring bean lifecycle and etc. Question : Where should we use BeanFactory and where should we use ApplicationContext container ? Answer : If in your application memory is big constraint then try to use BeanFactory otherwise we can use ApplicationContext container. ApplicationContext = Industry standard BeanFactory = Rarely used, basic container #Spring #SpringFramework #SpringBoot #Java #BeanFactory #ApplicationContext #DependencyInjection #JavaDeveloper

🚀 Day 14/100 - Dependency Injection (DI) - 1️⃣ One of the most important concepts in Spring Boot and modern backend development❗ ➡️ What is it? A design/programming technique where an object receives its dependencies from an external source (like the Spring container) instead of creating them itself. In simple words: 👉 Objects don’t create dependencies, they are provided. ➡️ Why to use? DI helps you write clean, scalable, and maintainable code: 🔹Promotes loose coupling between classes 🔹 Improves testability and maintainability 🔹 Encourages modular & reusable code 🔹 Follows SOLID principles - especially the "D: Dependency Inversion Principle" ➡️ Example: The attached image shows Dependency Injection via Constructor 👇 📌 Key Takeaway DI shifts responsibility from objects to the Spring container, making applications: - Easier to read - Easier to test - Easier to maintain Next post: https://lnkd.in/de9hpKXR Previous post: https://lnkd.in/dYC2XdM3 #100Days #SpringBoot #DependencyInjection #Java #BackendEngineering #SoftwareEngineering

🧩 The @SpringBootApplication annotation is a meta-annotation in Spring Boot that combines several other important annotations to streamline the configuration process. It marks the main class of a Spring Boot application as: ✨A configuration class for defining beans. ✨The starting point for component scanning. ✨A trigger for auto-configuration based on project dependencies. 🧩 By using @SpringBootApplication, developers can quickly bootstrap an application with sensible defaults, significantly reducing the need for manual or XML-based configuration, and allowing them to focus more on business logic. 🌱Advantages of @SpringBootApplication:- 🟦Reduces configuration complexity by combining multiple annotations. 🟦Automatically configures commonly used components based on classpath dependencies. 🟦Simplifies the application bootstrap process. 🟦Provides sensible defaults while allowing customization when needed. 🟦Supports a clean, convention-over-configuration approach. #SpringBoot #Java #BackendDevelopment #LearnSpring #JavaDeveloper #CodingBasics #SoftwareEngineering #CleanCode #Java #CodingTips #RESTAPI #WebDevelopment #SpringCore #SpringFramework #SoftwareArchitecture

🌱 Spring Bean Lifecycle — What REALLY Happens Behind the Scenes? Ever wondered what Spring actually does with your beans after you write @Component? Here’s the journey every Spring Bean goes through 👇 ➡️ Create – Spring instantiates the bean using constructors or factory methods ➡️ Configure – Dependencies are injected (@Autowired, @Value, setters) ➡️ Aware Phase – Bean becomes context-aware (BeanNameAware, ApplicationContextAware) ➡️ Initialize – Custom init logic runs (@PostConstruct, InitializingBean) ➡️ Use – Bean is fully ready and used across the application ➡️ Destroy – Cleanup happens gracefully (@PreDestroy, DisposableBean) 🧠 Why this matters in real projects Prevents bugs caused by using beans before they’re ready Helps design clean startup & shutdown logic Critical for microservices, resource management, and performance Essential for understanding Spring Boot auto-configuration 👉 One-liner to remember: Spring creates → configures → initializes → uses → destroys beans Mastering the lifecycle = mastering Spring 🚀 #Spring #SpringBoot #Java #BackendEngineering #Microservices #SystemDesign #SoftwareDevelopment #Learning

🚀 Day 12/100 - Spring Boot Annotations - 3️⃣ @Autowired & @Qualifier Dependency Injection (DI) in Spring boot is managed with the help of these two annotatios❗ ➡️ @Autowired 🔹What it does: Automatically injects a bean from the Spring container into another bean by type 🔹Where to use: - With class attributes - Constructors - Setter methods ➡️ @Qualifier 🔹What it does: Resolves conflicts when multiple beans of the same type exist 🔹When to use: - When there is disambiguity between multiple beans - To explicitly choosing which implementation to inject 💡 Key takeaway: @Autowired injects → @Qualifier decides which one. Next post: https://lnkd.in/dYC2XdM3 Previous post: https://lnkd.in/dtUTs85c #100Days #SpringBoot #Java #DependencyInjection #Annotations #BackendDevelopment #SoftwareEngineering

One of the most important pillars of structural software quality is coupling and decoupling. Decoupling means reducing how much one part of the system depends on another. When components know less about each other, the code becomes easier to maintain, test, and evolve. To reduce coupling between classes and objects, there are many design patterns that can be applied. Dependency Injection is a design pattern that allows objects to receive their dependencies instead of creating them directly. This removes tight coupling, because classes depend on abstractions rather than concrete implementations — making changes safer and cleaner. Using Spring Boot, we can make Dependency Injection much easier through annotations: @Component, @Service, @Repository → define beans without manual instantiation @Autowired → inject dependencies instead of creating them @Configuration + @Bean → control dependencies explicitly when needed By combining decoupling principles with Spring’s Dependency Injection, we can build systems that are more flexible, testable, and ready to scale. #Java #SpringBoot #SoftwareArchitecture #CleanCode #softwareengineering #Backend

🚀 Day 21/100 - Property Injection in Spring Boot How to bring configuration values into Spring Boot classes? Spring gives 2 options for this 👇 1️⃣ @Value Best for small, individual values ✔ Quick and lightweight ✔ Supports default (fallback) values ✔ Ideal for simple configs Example use cases 🔹Server port 🔹Feature flags 🔹Single custom values 2️⃣ @ConfigurationProperties Best for grouped / structured configuration ✔ Maps multiple related properties into a POJO ✔ Cleaner & more maintainable ✔ Ideal for complex configs Example use cases 🔹App metadata 🔹External service configs 🔹Feature-based settings 🧠 When to use what? 👉 Few values → @Value 👉 Structured configs → @ConfigurationProperties In real-world projects, both are used together for clean and scalable configuration management. Next post: https://lnkd.in/dbNhz8af Previous post: https://lnkd.in/djW2-Xh2 #100Days #SpringBoot #Java #BackendDevelopment #Configuration #PropertyInjection #WebDevelopment #SoftwareEngineering