How to write Query find Book by Category? - spring-data-jpa

Question

Suppose I have 2 tables: Book and Category.
I use Spring Data JPA
I want to get a list of books by category and view it on Thymeleaf as Category Menu
-> how should I write Query?
below is my way but it has no data
Book
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer id;
private String name;
#Column(length = 100)
private int isbn;
private String description;
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "categoryid")
private Category category;
Category
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer id;
#NotEmpty(message="Thể loại không được trống")
private String name;
#NotEmpty(message="Mã không được trống")
private String code;
#OneToMany(mappedBy = "category")
private List<Book> books = new ArrayList<>();
BookRepo
#Query(value = "SELECT b.* FROM book b INNER JOIN category c on b.name = c.id WHERE c.id = ?1", nativeQuery = true)
List<Book> findBookByCategory(Integer categoryId);
Controller
#GetMapping("/{category}")
public String getBookByProduct(#PathVariable("category") Integer category, Model model, HttpSession session) {
List<Book> bookList = bookService.findBookByCategory(category);
if(bookList == null) {
session.setAttribute("message", new MessageResponse("Không có Sách","danger"));
}
for(Book book : bookList ) {
System.out.println(book.toString());
}
model.addAttribute("category", bookList);
return "home/category";
}
View
<h4 class="text-uppercase font-weight-bold mb-3">Thể Loại</h4>
<div class="mt-2 mb-2 pl-2 ">
<div class="custom-control" th:each="category : ${category}" th:value="${category.id}">
<h5>
<a class="btn btn-info popovers" th:href="#{'/category/' + ${category.id}}" >[[${category.name}]]</a>
</h5>
</div>
</div>

Answer 1

hello this is the approach I used in my case;
in your repository interface
or
List<Book> findBookByCategoryId(Integer cId);
then in your service class implement the above repo methods
List<Book> bks= new ArrayList<>();
BookRepo.findBookByCategoryName("programming books")
.forEach(bks::add);
System.out.println(bks);
BookRepo.findBookByCategoryId(1)
.forEach(bks::add);
System.out.println(bks);