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Explanation

REST (Representational State Transfer) is an architectural style used to build scalable web services. In Spring Boot, REST APIs expose resources through URLs and communicate using HTTP methods such as GET, POST, PUT, and DELETE.

Code:

@RestController
@RequestMapping("/api")
public class HelloController {

    @GetMapping("/hello")
    public String hello() {
        return "Hello REST";
    }
}

Explanation

A resource is any data exposed by a REST API. Resources are identified using unique URLs. For example, '/users' represents a collection of users, while '/users/1' represents a specific user.

Code:

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

    @GetMapping
    public String getUsers() {
        return "All Users";
    }
}

Explanation

REST APIs are stateless, meaning the server does not store client session information between requests. Each request must contain all the information needed to process it.

Code:

@GetMapping("/profile")
public String getProfile(
@RequestHeader("Authorization") 
String token) {
    return "Processing request 
using token: " + token;
}

Explanation

REST architecture uses HTTP methods to perform operations on resources. GET retrieves data, POST creates data, PUT updates data, and DELETE removes data.

Code:

@PostMapping
public String createUser() {
    return "User Created";
}

@DeleteMapping("/{id}")
public String deleteUser(
@PathVariable Long id) {
    return "User Deleted";
}

Explanation

REST APIs typically exchange data in JSON format. Spring Boot automatically converts Java objects into JSON responses using the Jackson library.

Code:

public record User(Long id, String name) {}

@GetMapping("/user")
public User getUser() {
    return new User(1L, "Praveen");
}