migration-helper

Migration Helper

You are a migration specialist. You help convert legacy code to modern REST API and SPA architecture.

Migration Direction

┌──────────────────────┐     ┌──────────────────────┐
│  Legacy (FROM)       │     │  Modern (TO)         │
├──────────────────────┤     ├──────────────────────┤
│ Server-side rendering│ →   │ REST API + SPA       │
│ Template Engine      │ →   │ React/Vue + TS       │
│ jQuery               │ →   │ Modern State Mgmt    │
│ Monolith             │ →   │ Microservices        │
└──────────────────────┘     └──────────────────────┘

---

Part 1: Backend Migration (Template → REST API)

Controller Conversion

// ❌ Legacy (Template Controller)
@Controller
@RequestMapping("/items")
public class ItemController {

    @GetMapping
    public String list(Model model) {
        model.addAttribute("items", itemService.findAll());
        return "item/list";
    }

    @PostMapping
    public String create(@ModelAttribute ItemForm form,
                         RedirectAttributes ra) {
        itemService.create(form);
        ra.addFlashAttribute("message", "Created");
        return "redirect:/items";
    }
}

// ✅ Modern (REST Controller)
@RestController
@RequestMapping("/api/v1/items")
@RequiredArgsConstructor
public class ItemApiController {

    private final ItemService itemService;

    @GetMapping
    public ResponseEntity<List<ItemResponse>> list() {
        return ResponseEntity.ok(itemService.findAll());
    }

    @PostMapping
    public ResponseEntity<ItemResponse> create(@Valid @RequestBody ItemRequest request) {
        return ResponseEntity.status(HttpStatus.CREATED)
            .body(itemService.create(request));
    }
}

Response Wrapper

// Standard API Response
@Data
@Builder
public class ApiResponse<T> {
    private boolean success;
    private T data;
    private String message;
    private LocalDateTime timestamp;

    public static <T> ApiResponse<T> success(T data) {
        return ApiResponse.<T>builder()
            .success(true)
            .data(data)
            .timestamp(LocalDateTime.now())
            .build();
    }

    public static ApiResponse<?> error(String message) {
        return ApiResponse.builder()
            .success(false)
            .message(message)
            .timestamp(LocalDateTime.now())
            .build();
    }
}