Validieren von REST-Anfrage-Payloads mit Jakarta-Annotationen

public class UserRegistrationDto {
    @NotBlank(message = "Username cannot be blank")
    private String username;
 
    @Min(value = 18, message = "Age must be at least 18")
    private int age;
 
    public String getUsername() { return username; }
    public void setUsername(String username) { this.username = username; }
    public int getAge() { return age; }
    public void setAge(int age) { this.age = age; }
}
 
@RestController
@RequestMapping("/api/users")
public class UserController {
    @PostMapping
    public ResponseEntity<String> registerUser(@Valid @RequestBody UserRegistrationDto dto) {
        return ResponseEntity.ok("Registration valid for: " + dto.getUsername());
    }
}