package com.springmvc.controller;
...
import com.springmvc.validator.UnitsInStockValidator;

@Controller
@RequestMapping("/books")
public class BookController {

    @Autowired
    private BookService bookService;

    @Autowired
    // UnitsInStockValidator의 인스턴스 선언 
    private UnitsInStockValidator unitsInStockValidator; ➊
    ...
    @InitBinder
    public void initBinder(WebDataBinder binder) {
        binder.setValidator(unitsInStockValidator); // 생성한 unitsInStockValidator 설정 ➋
        binder.setAllowedFields("bookId", "name", "unitPrice", "author", "description",
                               "publisher", "category", "unitsInStock", "totalPages", 
                               "releaseDate", "condition", "bookImage");
    }
    ...
}