Can you explain what a REST controller is and how it is used in API development?

A REST controller is a component in a web application that handles HTTP requests and forms HTTP responses according to REST principles (Representational State Transfer).

In Java, especially with the Spring Framework, REST controllers are created using the @RestController annotation. They enable the implementation of APIs that interact with clients via standard HTTP methods (GET, POST, PUT, DELETE).

Main features of a REST controller:

• Routes requests based on URL.
• Handles data in JSON or XML format.
• Uses HTTP methods to define actions (e.g., GET — retrieve data, POST — create).

Example of a simple REST controller in Spring Boot:

@RestController
@RequestMapping("/users")
public class UserController {

    @GetMapping("/{id}")
    public User getUser(@PathVariable Long id) {
        // logic to get user by id
        return userService.findById(id);
    }

    @PostMapping
    public User createUser(@RequestBody User user) {
        // logic to create user
        return userService.save(user);
    }
}

This controller simplifies API creation, making it understandable and standardized.