Before diving into the world of Java web development, it is very important to understand how the client-server model works. It is necessary for you to understand the client-server model because all Java web applications are built on it. Please know everything about the different layers on the server. This will make your basics stronger and it will be easier to understand advanced Java. Because nowadays we are developing web apps using advanced java (Spring or Spring Boot), the client server will help you understand how the Spring/Spring Boot framework works.

annotations define the mapping of incoming HTTP requests to methods within the controller, allowing for seamless handling of client requests.

@Controller is used to declare common web controllers which can return HTTP response but @RestController is used to create controllers for REST APIs which can return JSON.

@GetMapping is only for HTTP GET request @RequestMapping can be used to process any HTTP methods like POST, PUT, GET and even DELETE.