Проблемы с валидацией

При добавлении invNum которого нету в базе все работает и добавляется, а вот если есть уже такой в базе то ошибка! класс валидации

@Component("bookValidator")
public class BookValidator implements Validator {
@Autowired
private CatalogBooksService catalogBooksService;
@Override
public boolean supports(Class<?> aClass) {
    return CatalogBooks.class.equals(aClass);
}
@Override
public void validate(@Nullable Object o, Errors errors) {
    CatalogBooks catalogBooks = (CatalogBooks) o;
    if (catalogBooksService.getCatalogBookByInvNum(catalogBooks.getInvNum()) != null){
        errors.rejectValue("invNum","jjj","Книга с таким инвентарным номером уже существует!");
    }
}

}

так получаю из базы существующий номер

 @Override
public CatalogBooks getCatalogBookByInvNum(int invNum) {
    CatalogBooks catalogBooks = (CatalogBooks) currentSession().createQuery("from CatalogBooks c where c.invNum =:inv")
            .setParameter("inv",invNum)
            .setMaxResults(1)
            .uniqueResult();
    return catalogBooks;
}

это контроллер

 @RequestMapping(value = "/bookAdd", method = RequestMethod.POST)
public String bookNew(@ModelAttribute @Valid CatalogBooks catalogBooks,
                        @ModelAttribute Category category,
                      BindingResult bindingResult,
                      Model model){
     bookValidator.validate(catalogBooks, bindingResult);
    if (bindingResult.hasErrors()){
        Map<String, String> errorsMap = ControllerUtils.getErrors(bindingResult);
        model.addAttribute("errorsMap", errorsMap);
        model.addAttribute("book", catalogBooks);
        model.addAttribute("category", categoryService.categoryList());
    }else {
        Category category1 = categoryService.getCategory(category.getId_Category());
        catalogBooks.setCategory(category1);
        catalogBooksService.addCatalogBook(catalogBooks);
        model.addAttribute("addOk", true);
    }
    model.addAttribute("category", categoryService.categoryList());
    return "/bookAdd";
}

Выскакивает ошибка

класс Category

@Entity
@Table(name = "categoryes")
public class Category {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column (name = "id_category")
private int id_Category;
@Column (name = "name")
private String categoryName;
@OneToMany(fetch = FetchType.LAZY, mappedBy = "category")
private Set<CatalogBooks> catalogBooks;
public Category() {
}
public int getId_Category() {
    return id_Category;
}
public void setId_Category(int id_Category) {
    this.id_Category = id_Category;
}
public String getCategoryName() {
    return categoryName;
}
public void setCategoryName(String categoryName) {
    this.categoryName = categoryName;
}
public Set<CatalogBooks> getCatalogBooks() {
    return catalogBooks;
}
public void setCatalogBooks(Set<CatalogBooks> catalogBooks) {
    this.catalogBooks = catalogBooks;
}
@Override
public String toString() {
    return "Category{" +
            "id_Category=" + id_Category +
            ", categoryName='" + categoryName + '\'' +
            //", catalogBooks=" + catalogBooks +
            '}';
}

}

класс CatalogBooks

@Entity
@Table(name = "catalog_books")
public class CatalogBooks {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "id_catalog_book")
private int id;
@ManyToOne(fetch = FetchType.EAGER)
@JoinColumn(name = "category_id")
private Category category;
@OneToMany(fetch = FetchType.LAZY, mappedBy = "catalogBooks")
Set<Give> gives;
@NotBlank(message = "Название книги не может быть пустым")
@Column (name = "name")
private String name;
@Column (name = "author")
private String author;
@Column (name = "year")
private int year;
@Column (name = "inv_num")
private int invNum;
@Column (name = "count_book")
private int countBook;
public CatalogBooks(){
}
public int getId() {
    return id;
}
public void setId(int id) {
    this.id = id;
}
public Category getCategory() {
    return category;
}
public void setCategory(Category category) {
    this.category = category;
}
public String getName() {
    return name;
}
public void setName(String name) {
    this.name = name;
}
public String getAuthor() {
    return author;
}
public void setAuthor(String author) {
    this.author = author;
}
public int getYear() {
    return year;
}
public void setYear(int year) {
    this.year = year;
}
public int getInvNum() {
    return invNum;
}
public void setInvNum(int invNum) {
    this.invNum = invNum;
}
public int getCountBook() {
    return countBook;
}
public void setCountBook(int countBook) {
    this.countBook = countBook;
}
@Override
public String toString() {
    return "CatalogBooks{" +
            "id=" + id +
            ", category=" + category +
            ", name='" + name + '\'' +
            ", author='" + author + '\'' +
            ", year=" + year +
            ", invNum=" + invNum +
            ", countBook=" + countBook +
            '}';
}

}