Lapisan Perkhidmatan CRUD

import jakarta.persistence.*;@Entity
public class User {
  @Id @GeneratedValue
  private Long id;
  private String name;
  // getters/setters omitted
}

import org.springframework.stereotype.Service;import java.util.*;
@Service
public class UserService {
  private final UserRepository repo;
  public UserService(UserRepository repo) { this.repo = repo; }

  public List<User> all() { return repo.findAll(); }
  public User add(User u) { return repo.save(u); }
  public Optional<User> find(Long id) { return repo.findById(id); }
  public void delete(Long id) { repo.deleteById(id); }
}

import org.springframework.web.bind.annotation.*;import java.util.*;@RestController
@RequestMapping("/users")
public class UserController {
  private final UserService service;
  public UserController(UserService service) { this.service = service; }

  @GetMapping
  public List<User> all() { return service.all(); }

  @PostMapping
  public User add(@RequestBody User u) { return service.add(u); }

  @GetMapping("/{id}")
  public User one(@PathVariable Long id) { return service.find(id).orElse(null); }

  @DeleteMapping("/{id}")
  public void delete(@PathVariable Long id) { service.delete(id); }
}