Spring Boot 3 + Java 21 = modern Java backend. Auto-configuration, dependency injection, huge ecosystem.
REST API¶
@RestController @RequestMapping(“/api/users”) public class UserController { private final UserRepository repo; public UserController(UserRepository repo) { this.repo = repo; } @GetMapping public List findAll() { return repo.findAll(); } @PostMapping @ResponseStatus(HttpStatus.CREATED) public User create(@Valid @RequestBody User user) { return repo.save(user); } @GetMapping(“/{id}”) public User findById(@PathVariable Long id) { return repo.findById(id) .orElseThrow(() -> new ResponseStatusException(HttpStatus.NOT_FOUND)); } }
JPA Entity¶
@Entity public class User { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Long id; @NotBlank private String name; @Email private String email; // getters, setters } public interface UserRepository extends JpaRepository { List findByNameContaining(String name); }
Key Takeaway¶
Spring Boot 3 + Java 21 + virtual threads = modern Java. JPA for the database, Spring Security for auth.