Building REST APIs

REST (Representational State Transfer) is the standard architectural style for web APIs.

Annotations for REST

• @RestController: Tells Spring this class handles web requests.
• @GetMapping("/path"): Handles HTTP GET requests.
• @PostMapping("/path"): Handles HTTP POST requests.
• @PathVariable: Extracts values from the URL.
• @RequestBody: Extracts data from the request body (JSON).

Example Controller

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

    @GetMapping
    public List<String> getUsers() {
        return List.of("Alice", "Bob");
    }

    @GetMapping("/{id}")
    public String getUserById(@PathVariable int id) {
        return "User ID: " + id;
    }

    @PostMapping
    public String createUser(@RequestBody String name) {
        return "User " + name + " created!";
    }
}

Request & Response

Spring Boot uses Jackson to automatically convert Java objects to JSON and vice versa.

@GetMapping("/me")
public User getMe() {
    return new User("John", 25); 
    // Returns: { "name": "John", "age": 25 }
}

Interactive Code

We can't run a real server here, but we can model the logic!

Quiz

Next Steps

We built it. Does it work? Let's verify with Testing.