Designing for Failure in Java and Spring Boot

🚀 PUT vs PATCH in Spring Boot — Are You Using Them Correctly?🚀 One small mistake I often see in Spring Boot projects is mixing up PUT and PATCH in REST APIs, or even some programmers keep using other alternatives like POST. They both update data… but they are NOT the same. 🔁 PUT = Full Update or replacing the entire object. When using @PutMapping, you’re expected to send the entire object. If a field is missing, it may be overwritten or set to null, unless it should be not null which may cause errors. 🩹 PATCH = Partial Update With @PatchMapping, you update only the fields you send. Unsent fields remain unchanged. If you're building clean, scalable APIs: Use PUT for full updates Use PATCH for partial updates Clean APIs = predictable behavior = better maintainability. #SpringBoot #Java #RESTAPI #BackendDevelopment #SoftwareEngineering #linkedin #network #Development #Controllers

At 3:30 AM, I stopped debugging the code. The bug wasn’t in my code. At least… that’s what I thought. It was 2:00 AM when I stopped writing the code and started testing it. The Student Feedback System built using Java Spring Boot was ready. JWT (JSON Web Token) authentication was implemented. Database connected. Endpoints responding. Everything looked stable. Until I tested the login flow. Every login attempt failed. No compilation errors. No stack traces. No crashes. Just silent authentication rejection. I checked the controller. Reviewed the service layer. Added logs. Restarted the application. Time passed. 2:45 AM. 3:10 AM. Still broken. And at 3:30 AM, I stopped debugging the code. That’s when I looked beyond the logic. The token expiration was calculated using one timezone, but validation was happening in another. I had generated the expiry using LocalDateTime.now() while validation was comparing it against a UTC-based time reference (similar to Instant.now()). Which meant the token was technically expired the moment it was created. Spring Security wasn’t failing. The backend wasn’t broken. The system was behaving exactly as configured. My assumption was wrong. That night changed how I approach debugging. Most real-world bugs aren’t syntax errors. They’re environment mismatches. Configuration inconsistencies. Context problems. Now before rewriting logic, I check: • System time • Timezone handling • Environment variables • application .properties • Token expiry configuration • Server logs Because sometimes… The difference between a working backend and a broken one is just two clocks speaking different languages. ⸻ #Java #SpringBoot #BackendDevelopment #SoftwareEngineering #Programming #Debugging #Developers #TechLearning #WebDevelopment #GrowthMindset

⚡ One Skill That Makes a Strong Backend Developer: Debugging Writing code is important, but debugging is where real learning happens. In backend development with Java and Spring Boot, issues can come from many places: 🔹 Database queries 🔹 API integrations 🔹 Configuration problems 🔹 Exception handling 🔹 Performance bottlenecks Understanding logs, stack traces, and system behavior is essential for identifying the root cause of problems. A developer who can quickly debug and resolve issues adds huge value to any engineering team. Debugging is not just fixing bugs — it’s understanding how systems actually work. What debugging techniques help you solve problems faster? 👇 #Java #SpringBoot #BackendDeveloper #Debugging #SoftwareEngineering

🚀 What actually happens when a request hits a Spring Boot application? Many developers use Spring Boot daily, but understanding the internal flow of a request helps you write cleaner and better backend code. Here is the simplified flow: 1️⃣ Client Request Browser or Postman sends an HTTP request Example: "POST /api/users" 2️⃣ DispatcherServlet Spring’s front controller receives the request and routes it to the correct controller. 3️⃣ Controller Layer "@RestController" receives the request, validates input, and delegates the work to the service layer. 4️⃣ Service Layer "@Service" contains the business logic such as validation, processing, and transformations. 5️⃣ Repository Layer "JpaRepository" interacts with the database and executes SQL queries. 6️⃣ Response to Client Spring converts the Java object to JSON (via Jackson) and sends it back with HTTP 200 OK. --- 🔑 Golden Rules ✅ Controller → HTTP only ✅ Service → Business logic ✅ Repository → Database operations ✅ Each layer has one responsibility (SRP) This layered architecture makes Spring Boot applications clean, testable, and scalable. #Java #SpringBoot #SpringFramework #Backend #SoftwareEngineering #Programming #Developer #Tech #CleanCode #JavaDeveloper

🚀 Day 55/100 - Spring Boot - Logging Once your application is running in production, System.out.println() is not enough ❌ You need structured, configurable, and production-ready logging❗ For that, spring boot uses: 🔹SLF4J (Logging API / facade) 🔹Logback (Default implementation) ➡️ Why Logging Matters? Because it helps you: ✔ Monitor application behavior ✔ Debug issues in production ✔ Track errors ✔ Audit important events ✔ Analyze system health Good logging = easier debugging = better reliability ➡️ SLF4J and Logback 🔹 SLF4J (Simple Logging Facade for Java) 🔹It’s a logging abstraction 🔹Allows switching logging frameworks (Logback, Log4j, etc.) 🔹Spring Boot includes it by default Think of it as an interface for logging. ➡️ Basic Logging Example (see attached image 👇) ➡️ Different Log Levels & their Purpose TRACE: used for very detailed debugging DEBUG: used for development debugging INFO: used for general application events WARN: used for something unexpected ERROR: used for serious problems ➡️ Best Practices ✔ Use INFO for important business events ✔ Use WARN for suspicious behavior ✔ Use ERROR for failures ✔ Avoid excessive logging Previous post: https://lnkd.in/dZVkgwcD #100Days #SpringBoot #Logging #SLF4J #Logback #Java #BackendDevelopment #WebDevelopment #SoftwareEngineering

Day 12 – Exception Handling in Spring Boot (Handling Failures Properly) Building APIs is not enough. Today I focused on how to handle errors properly in real-world backend applications. Why Exception Handling is important: Every application will fail at some point The way you handle failures defines your system quality Problems without proper handling: * Unclear error messages * Exposed internal details * Poor user experience * Difficult debugging How Spring Boot handles exceptions: @ExceptionHandler – Handle specific exceptions @ControllerAdvice – Global exception handling @ResponseStatus – Customize HTTP status codes Real-world approach (Important): Create a Global Exception Handler Return standard error response format Log errors properly Never expose internal stack traces to clients Example error response structure: { "timestamp": "...", "status": 400, "error": "Bad Request", "message": "Invalid input data" } Why this matters in real projects: Makes APIs professional and reliable Improves debugging and monitoring Provides better client-side experience Mandatory in microservices communication Handling failure correctly is what makes you a real backend developer. #Java #SpringBoot #SpringFramework #BackendDevelopment #Microservices #LearningInPublic

Laying the foundation for stronger backend systems. I’ve started setting up the backend foundation of my project using Java & Spring Boot. Focused on: • Structuring the project properly • Implementing Controller → Service → Repository layering • Configuring database connectivity Realizing that strong backend systems start with clean architecture not just working endpoints. Building step by step. 🚀 #Java #SpringBoot #BackendDeveloper #SoftwareEngineering #BuildingInPublic

🚀 Spring Boot Annotations Every Backend Developer Must Master Spring Boot may look simple from the outside… But the real magic lies in its annotations 🔥 Building APIs is easy. Designing secure, scalable, production-grade systems? That’s where annotations shine. Here are the ones I use the most in real-world projects: 🔹 Application Bootstrapping @SpringBootApplication @EnableAutoConfiguration @ComponentScan 🔹 Dependency Injection @Autowired @Qualifier @Primary 🔹 REST APIs @RestController @RequestMapping @GetMapping / @PostMapping / @PutMapping / @DeleteMapping 🔹 Database & JPA @Entity @Id @Transactional @Repository 🔹 Validation @NotNull @NotBlank @Size @Email 🔹 Exception Handling @ExceptionHandler @ControllerAdvice @RestControllerAdvice 🔹 Security (Production Level) @EnableWebSecurity @PreAuthorize @Secured Spring Boot isn’t just about writing controllers. It’s about clean architecture, layered design, transaction management, validation, and security. 💬 Which annotation do you use the most in your projects? #Java #SpringBoot #BackendDevelopment #Microservices #SystemDesign #JWT #SoftwareEngineering #LearningInPublic

Day 19 – Exception Handling in Spring Boot Today I focused on handling exceptions properly in Spring Boot applications. Exception handling is important for building reliable and production-ready APIs. Instead of exposing raw errors, we should return meaningful and structured responses. =>@ControllerAdvice Used to handle exceptions globally across the entire application. It allows centralized error handling instead of writing try-catch blocks in every controller. =>@ExceptionHandler Used to handle specific exceptions. It defines what response should be returned when a particular exception occurs. => Custom Exceptions Creating custom exception classes improves clarity. For example, throwing a ResourceNotFoundException when data is not found makes the API more meaningful. => Proper exception handling improves: Code cleanliness User-friendly error responses Maintainability API reliability Structured exception handling is essential for building production-ready and maintainable backend systems. #Day19 #SpringBoot #ExceptionHandling #Java #BackendDevelopment #LearningJourney