Circular Dependency in Spring Boot: Causes and Fixes

Most Spring Boot developers ship to production without knowing if their app is truly healthy. 🩺 You test your endpoints. Your CI passes. You deploy. But the moment something silently breaks, a database connection drops, an external API becomes unreachable, disk space runs out , your application keeps running, no errors, no alerts, just quietly serving failures to your users. That's the problem Health Checks solve. And Spring Boot makes it almost too easy to get right. 🩺 What is a Health Check? A simple mechanism that answers one question on a schedule: "Is this service actually ready to serve traffic?" Not just "is the JVM running?" — but "are all the pieces this app depends on working?" ⚡ Spring Boot Actuator , built-in and ready Add one dependency and you instantly get a /actuator/health endpoint that checks your database, MongoDB, disk space and more, automatically. UP ➡️ all good, serve traffic. DOWN ➡️ something is wrong, alert immediately. No custom code needed to get started. 🔧 But the real power is in custom indicators The default tells you if the app is alive. Custom health indicators tell you if your app is useful. You can write checks for anything: an external payment API, a message queue, a critical cache, if that dependency is down, your health endpoint reflects it, and your infrastructure reacts automatically. 💡 Two checks every production app needs: Liveness ➡️Is the app alive? Should it be restarted? Readiness➡️ Is the app ready to receive traffic? These two signals are especially critical in Kubernetes, they drive automatic restarts and traffic routing without any manual intervention. Are you using custom health indicators in your Spring Boot apps? Or just relying on the defaults? 👇 #Java #SpringBoot #HealthCheck #BackendDevelopment #SoftwareArchitecture #LearningInPublic #Kubernetes #Programming

🚨 Ever wondered what actually happens when a Spring Boot app starts? Most developers just run the app and move on. But understanding this helped me debug startup issues faster. Here’s the simplified flow 👇 Spring Boot initializes the ApplicationContext Auto-configuration kicks in (based on classpath) Beans are created and wired Embedded server (Tomcat) starts Application is ready to serve requests 💥 Real issue I faced: A misconfigured bean was slowing startup by ~20 seconds. Root cause? Unnecessary component scanning + heavy initialization logic inside a bean. ✅ Fix: Reduced scan scope Moved heavy logic to lazy initialization 💡 Takeaway: Startup time matters more than you think in microservices. Have you ever debugged a slow Spring Boot startup? #Java #SpringBoot #BackendDevelopment #SoftwareEngineering  #Microservices #RESTAPI #SystemDesign  #DeveloperLife #100DaysOfCode

🚀 Day 17/100: Spring Boot From Zero to Production Topic: Activating Profiles in Spring Boot -> Why Activation Matters Creating profiles isn’t enough You need to activate them to use their config Otherwise, Spring Boot falls back to the default profile. -> Method 1: JVM Argument Pass this when running your app: -Dspring.profiles.active=dev Common for: Local development Switching configs quickly Loads application-dev.yaml -> Method 2: Environment Variable Set: SPRING_PROFILES_ACTIVE=dev Best for: Production environments CI/CD pipelines -> Default Behavior No active profile? default gets loaded Others are ignored Quick Insight Profiles = Config separation Activation = Making them work Simple concept. Powerful impact. This might sound simple but stay consistent. We’re building production mindset step by step. #Java #SpringBoot #SoftwareDevelopment #100DaysOfCode #Backend

Your Spring Boot app works perfectly… Until it doesn’t in production. Same code. Different behavior. Why? 𝗣𝗿𝗼𝗳𝗶𝗹𝗲𝘀 This is one of the most underrated features in Spring Boot. When you build an application, you don’t run it in just one environment. You usually have:  • Development (dev)  • Testing (test)  • Production (prod) And here’s the problem: Each environment needs different configurations. Different databases Different APIs Different logging levels You can’t hardcode all of this. That’s where Spring Boot Profiles come in. What do profiles do? They let you 𝘀𝘄𝗶𝘁𝗰𝗵 𝗰𝗼𝗻𝗳𝗶𝗴𝘂𝗿𝗮𝘁𝗶𝗼𝗻𝘀 based on the environment — without changing your code. Spring boot lets you manage this using .𝗽𝗿𝗼𝗽𝗲𝗿𝘁𝗶𝗲𝘀 or .𝘆𝗺𝗹 files, where each profile has its own dedicated configurations And you just activate it like: spring.profiles.active=prod Done. Your entire app behaves differently. Why this is powerful: No more “it works on my machine” issues Clean separation of environments Safer deployments Easy testing without breaking production Profiles are a small feature… But they solve a big real-world problem. Next time you build a Spring Boot app, Don’t just run it — run it with the right profile. #CoreJava #JavaDeveloper #SpringFramework #SpringBoot #Profiles #BackEndDevelopment #SoftwareEngineering #Programing #Developers #WebDevelopment #Environments #Microservices #aswintech

Spring Boot doesn't run your app. You don't know what does. 🤯 Most devs have shipped 3 projects without reading a single auto-configuration class. When an interviewer asks "how does Spring Boot work internally" — they blank. 😶 Here's what actually happens when you run your app: 👇 → JVM starts, Spring Application Context initializes → @SpringBootApplication triggers 3 annotations at once → @EnableAutoConfiguration scans the classpath → Finds META-INF/spring/org.springframework.boot.autoconfigure.AutoConfiguration.imports → Loads ~150+ configuration classes conditionally The key word is conditionally. 🔑 @ConditionalOnClass → only loads if a class exists in classpath. @ConditionalOnMissingBean → only loads if YOU haven't defined one @ConditionalOnProperty → only loads if a property is set This is why adding one dependency changes your app's behavior. Not magic. Conditional class loading. ✅ Where to actually look: 🔍 → Open any *AutoConfiguration class in your IDE → Read the @Conditional annotations at the top → That's your app's real wiring diagram Most devs add spring-boot-starter-* and move on. 🚶 The ones who read the source code answer interview questions differently. 💡 Have you ever read a Spring Boot AutoConfiguration class top to bottom? Which one? #SpringBoot #Java #BackendDevelopment #SpringInternals

Do you also think building apps is complicated? Setting up everything… connecting pieces… making it all work together. But what if you could just focus on your idea? That’s what Spring Boot does. It takes care of the heavy lifting in the background, so you can build faster, with less stress - and actually enjoy the process. Think less setup. More building. 🚀 #SpringBoot #Java #BackendDevelopment #SoftwareEngineering #CleanCode #DeveloperLife

Your Spring Boot app works fine… Dependencies are getting injected… Everything looks clean. But there’s a hidden problem @𝗔𝘂𝘁𝗼𝘄𝗶𝗿𝗲𝗱 field injection Most beginners use it like this: @𝗔𝘂𝘁𝗼𝘄𝗶𝗿𝗲𝗱 𝗽𝗿𝗶𝘃𝗮𝘁𝗲 𝗨𝘀𝗲𝗿𝗦𝗲𝗿𝘃𝗶𝗰𝗲 𝘂𝘀𝗲𝗿𝗦𝗲𝗿𝘃𝗶𝗰𝗲; It works. But that doesn’t mean it’s right. What’s the hidden cost? 🔸 Harder to test You can’t easily mock dependencies without reflection or Spring context 🔸 Breaks immutability Fields can’t be final → objects become mutable 🔸 Hidden dependencies From outside, it’s not clear what your class depends on 🔸 Tight coupling with Spring Your class depends on the framework to work properly Now here’s the better approach: 𝗖𝗼𝗻𝘀𝘁𝗿𝘂𝗰𝘁𝗼𝗿 𝗜𝗻𝗷𝗲𝗰𝘁𝗶𝗼𝗻 𝗽𝗿𝗶𝘃𝗮𝘁𝗲 𝗳𝗶𝗻𝗮𝗹 𝗨𝘀𝗲𝗿𝗦𝗲𝗿𝘃𝗶𝗰𝗲 𝘂𝘀𝗲𝗿𝗦𝗲𝗿𝘃𝗶𝗰𝗲; 𝗽𝘂𝗯𝗹𝗶𝗰 𝗨𝘀𝗲𝗿𝗖𝗼𝗻𝘁𝗿𝗼𝗹𝗹𝗲𝗿(𝗨𝘀𝗲𝗿𝗦𝗲𝗿𝘃𝗶𝗰𝗲 𝘂𝘀𝗲𝗿𝗦𝗲𝗿𝘃𝗶𝗰𝗲) {   𝘁𝗵𝗶𝘀.𝘂𝘀𝗲𝗿𝗦𝗲𝗿𝘃𝗶𝗰𝗲 = 𝘂𝘀𝗲𝗿𝗦𝗲𝗿𝘃𝗶𝗰𝗲; } Why this is better:  • Makes dependencies explicit  • Easy unit testing (no Spring needed)  • Supports immutability (final fields)  • Fails fast if dependency is missing ⚡ And the best part? In modern Spring Boot, you don’t even need @Autowired on constructors. It just works. 💡 Real insight Field injection is convenient for small demos. Constructor injection is what survives in 𝗿𝗲𝗮𝗹 𝗽𝗿𝗼𝗷𝗲𝗰𝘁𝘀. Next time you write @Autowired, pause for a second… And ask: “Is there a better way?” #SpringBoot #CoreJava #SpringFramework #BackendDevelopment #BackEnd #SoftwareEngineering #SpringAnnotations #Programming #Developers #RealtimeProjects #Microservices #systemdesign #aswintech

Your Spring Boot app is probably a monolith in disguise. Here's how to tell: 1. One change = full redeployment 2. 50+ beans in a single context and nobody knows why 3. Shared database between "microservices" 4. Every service talks to every other service 5. Your docker-compose.yml is longer than your README If 3 or more hit home — you don't have microservices. You have a distributed monolith with extra network calls. The fix isn't more services. It's better boundaries. Start here: → Define clear domain ownership → One service = one database → Communicate through events, not direct calls → Deploy independently or it's not a microservice The goal was never "more services." It was "less coupling." Save this for your next architecture review. ♻️ Repost if your team needs to see this. Follow Kuldeep Singh for more real-world system design tips. #SystemDesign #SpringBoot #Microservices #SoftwareArchitecture #Java #BackendDevelopment #TechTips #Developers

🚀 Spring Configuration — The Backbone of Every Spring Boot App When I first started learning Spring Boot, I thought configuration was just “setup stuff.” Turns out… it’s the brain behind everything 🧠 🔹 What is Spring Configuration? It’s how you tell Spring: ✔️ What objects (beans) to create ✔️ How they connect (Dependency Injection) ✔️ How your app should run 🔹 3 Ways to Configure in Spring Boot 1️⃣ Annotation-Based (Most Common) Use "@Component", "@Service", "@Autowired" 👉 Clean, simple, and widely used 2️⃣ Java-Based Configuration Use "@Configuration" + "@Bean" 👉 Gives you full control when needed 3️⃣ application.properties / application.yml 👉 Configure ports, DB, and custom values 🔹 The Magic Annotation ✨ "@SpringBootApplication" It combines: - "@Configuration" - "@EnableAutoConfiguration" - "@ComponentScan" 👉 That’s why Spring Boot feels so easy! 🔹 Realization 💡 Spring Configuration is not just setup… It’s what makes your app: ✔️ Scalable ✔️ Maintainable ✔️ Production-ready 💬 My Take: If you truly understand configuration, you stop “using Spring” …and start thinking like Spring. #SpringBoot #Java #BackendDevelopment #LearnInPublic #Developers #CodingJourney

🚀 Day 88/100 - Spring Boot - Docker 🐳 Dockerizing Your Spring Boot Application Docker is a widely used technology which lets you package your app with all its dependencies into a portable container, so that it runs the same everywhere.. Here are some basic docker commands: ➡️ Creating a Dockerfile FROM openjdk:21 COPY target/myapp.jar app.jar ENTRYPOINT ["java", "-jar", "/app.jar"] 🔹Uses Java 21 base image 🔹Copies your built JAR 🔹Runs the app inside the container ➡️ Build Docker Image docker build -t myapp 🔹Creates an image named myapp ➡️ Run the Container docker run -p 8080:8080 myapp 🔹App will be available at: http://localhost:8080 ⚠️ Some Tips About Docker 🔹Use .dockerignore to reduce image size 🔹Use smaller base images for optimization 🔹Externalize configs using environment variables Previous post: https://lnkd.in/dkrCtq22 #100Days #SpringBoot #Docker #DevOps #Java #Microservices #BackendDevelopment #WebDevelopment #SoftwareEngineering