Hardy Tambeck’s Post

Understanding Key Annotations in Spring Boot Annotations make Spring Boot development simple and powerful. Let’s look at three important ones 👇 🔹 @Entity → Represents a table in the database → Each instance of the class maps to a row → Used in the data layer 🔹 @RestController → Handles HTTP requests and returns responses → Used to build REST APIs → Combines @Controller + @ResponseBody 🔹 @Service → Contains business logic of the application → Acts as a bridge between Controller and Repository ✅ In simple terms: • @RestController → Handles requests • @Service → Processes logic • @Entity → Represents data Understanding these annotations helps you see how different layers in Spring Boot work together. #SpringBoot #Java #BackendDevelopment #LearningInPublic #DeveloperGrowth

Why @Transactional is Your Best Friend in Spring In Spring Boot, the @Transactional annotation serves as your safety net. It guarantees that a series of database operations either all succeed or all fail together, embodying the "Atomic" aspect of ACID principles. Why it matters: • Data Integrity: Prevents "orphaned" records if the second step of a process crashes. • Automatic Rollback: If a RuntimeException occurs, Spring automatically undoes the changes. • Simplified Code: Eliminates the need to manually write session.begin() or commit(). The "Golden Rule" for New Developers: Always place @Transactional on the Service Layer, not the DAO/Repository. This ensures the entire business logic unit is protected. #SpringBoot #Java #Backend #CodingTips #Microservices #SoftwareEngineering

📌 Spring Boot Annotation Series Part 19 – @DeleteMapping @DeleteMapping is used to handle HTTP DELETE requests in a REST API. It is part of Spring Framework and is commonly used in RESTful services built with Spring Boot. 🔹 Why Do We Use @DeleteMapping? In REST APIs: GET → Fetch data POST → Create data PUT → Update data DELETE → Remove data @DeleteMapping handles delete operations. 🔹 What Happens Internally? @DeleteMapping is a shortcut for: @RequestMapping(method = RequestMethod.DELETE) So it is a specialized version of @RequestMapping. 🔹 In Simple Words @DeleteMapping connects an HTTP DELETE request to a controller method to remove a resource. #SpringBoot #Java #RESTAPI #DeleteMapping #BackendDevelopment #InterviewPreparation

Hi everyone 👋 📌 Spring Boot Annotation Series Part 18 – @PostMapping The @PostMapping annotation is used to handle HTTP POST requests in a Spring Boot application. It is part of the Spring Framework and is mainly used to create new resources in REST APIs. 🔹 What is @PostMapping? @PostMapping is a shortcut for: @RequestMapping(method = RequestMethod.POST) It makes the code cleaner and more readable. 🔹 When Do We Use POST? ✔ To create new data ✔ To submit form data ✔ To send request body (JSON/XML) ✔ When data is modified on the server Example use cases: Create a new user Place an order Register a customer Submit login details 🔹 Basic Example - @RestController @RequestMapping("/api/users") public class UserController { @PostMapping public String createUser(@RequestBody String user) { return "User created: " + user; } } 👉 Handles: POST http://localhost:8080/api/users 🔹 In Simple Words @PostMapping handles create operations in REST APIs. When a POST request hits the URL, Spring executes the mapped method and processes the request body. #SpringBoot #Java #RESTAPI #BackendDevelopment #InterviewPreparation #LearningInPublic

When building APIs in Spring Boot, you’ll see multiple mapping annotations. But what’s the difference? @RequestMapping → Generic mapping (can handle all HTTP methods) @GetMapping → Used for GET requests (fetch data) @PostMapping → Used for POST requests (create data) Example: @RestController @RequestMapping("/users") public class UserController { @GetMapping public List<String> getUsers() { return List.of("A", "B"); } @PostMapping public String createUser() { return "User created"; } } Modern Spring Boot prefers specific annotations like @GetMapping for clarity. Rule of thumb: GET → Read POST → Create PUT → Update DELETE → Remove Next post: What is @PathVariable and @RequestParam #Java #SpringBoot #APIDevelopment #BackendDevelopment

Spring Boot: Understanding the Internal Request Flow 🚀 Ever wondered what actually happens inside a Spring Boot application when a request is sent? Here’s a simplified breakdown of the internal flow: 1️⃣ Dispatcher Servlet Every HTTP request (from browser, Postman, or mobile) first reaches the Dispatcher Servlet. It acts as the central entry point that manages and routes all incoming requests. 2️⃣ Handler Mapping The Dispatcher Servlet consults Handler Mapping to identify which controller method should handle the incoming request URL. 3️⃣ Controller Layer (@RestController) Once identified, the appropriate controller method is invoked to handle the request. 4️⃣ Service Layer (@Service) The controller delegates business logic to the service layer, ensuring proper separation of concerns. 5️⃣ Data Access Layer (@Repository) The service interacts with the repository layer, which communicates with the database using Spring Data JPA. 6️⃣ Database Interaction The query is executed in the database, and results flow back through the layers: Database → Repository → Service → Controller → Dispatcher Servlet 7️⃣ Serialization (Jackson) With @RestController, Spring skips the View Resolver. Instead, Jackson automatically converts Java objects into JSON/XML format. 8️⃣ HTTP Response Finally, the serialized response is sent back to the client in a clean and efficient way. 💡 Key Insight @RestController = @Controller + @ResponseBody This is why Spring Boot directly returns data instead of resolving views—making REST APIs lightweight and high-performing. #SpringBoot #Java #BackendDevelopment #SpringFramework #RESTAPI #SoftwareEngineering #JavaDeveloper

🚀 Spring Boot Internals Series – Part 3 Ever seen this error? 👉 404 Not Found 👉 405 Method Not Allowed And thought: “My controller is correct… why is this not working?” You’re not alone. The issue is often NOT your code. It’s how Spring is trying to find your method. --- 🔍 Who decides which method gets called? 👉 HandlerMapping This is the component that tells Spring: “Which controller method should handle this request?” --- ⚙️ What actually happens When a request comes in: 1️⃣ DispatcherServlet receives the request 2️⃣ It asks HandlerMapping 3️⃣ HandlerMapping scans all controllers 4️⃣ Matches URL + HTTP method 5️⃣ Returns the correct handler method --- 🧠 Example @GetMapping("/users") public List<User> getUsers() { return userService.getUsers(); } If your request is: GET /users 👉 It matches perfectly ✅ But if your request is: POST /users 👉 No match ❌ → 405 error --- ⚠️ Why developers struggle Because we assume: “If the method exists, it will be called” But Spring checks: - URL path - HTTP method (GET/POST/PUT/DELETE) - Request mappings If anything doesn’t match → request fails --- 💡 Key takeaway Spring doesn’t “guess” your method. 👉 It strictly matches request → mapping Understanding this saves hours of debugging. --- 📌 Next post: I’ll break down how Spring converts request data into Java objects (Data Binding) Follow if you want to understand backend systems deeply. #SpringBoot #JavaDeveloper #BackendDeveloper #SoftwareEngineering #Microservices #LearningInPublic

Good evening LinkedIn connections 👋 Quick backend lesson I learned recently 👇 🚀 JOIN vs N+1 Problem Fetching related data inside loops can lead to the N+1 query problem. Example: 1 query to fetch users 100 queries to fetch related data = 201 database calls 😅 Instead, a proper JOIN can fetch everything in 1 optimized query. Small architectural decisions make a huge difference in performance and scalability. Are you careful about N+1 in your APIs? #BackendDevelopment #Java #SpringBoot #JPA #Performance #SoftwareEngineering

⚡ One common mistake many Spring Boot beginners make: using Entities directly in APIs. In real-world applications, developers usually separate Entity and DTO classes. But why? --- 🔹 Entity An Entity represents the database table and is used by JPA/Hibernate to interact with the database. Example: @Entity public class User { @Id private Long id; private String name; private String email; } Entities are mainly used in the Repository and Database layer. --- 🔹 DTO (Data Transfer Object) A DTO is used to transfer data between layers, especially between the backend and client (API response/request). Example: public class UserDTO { private String name; private String email; } DTOs are mainly used in the Controller layer. --- 📌 Why use DTO instead of Entity in APIs? ✔ Protects sensitive data ✔ Avoids exposing database structure ✔ Improves security ✔ Allows custom API responses --- 💡 Typical Flow in Spring Boot Client → Controller → DTO → Service → Entity → Repository → Database --- Using DTOs helps keep applications clean, secure, and scalable. #Java #SpringBoot #BackendDevelopment #SoftwareEngineering #JavaDeveloper #CleanArchitecture