TestSpringBoot.java

@Entity
@Setter
@Getter
public class Book {
    @Id
    @GeneratedValue
    private Long id;
    private String name;
    private String genre;
}

public interface BookRepository extends JpaRepository<Book, Long> { }

@RestController
@RequestMapping("/rest")
public class Controller {
    private BookRepository bookRepository;

    @Autowired
    public void setBookRepository(BookRepository bookRepository) {
        this.bookRepository = bookRepository;
    }

    @GetMapping("/books")
    public List<Book> getBooks() {
        return bookRepository.findAll();
    }

    @GetMapping("/book/{id}")
    public Book getBookById(@PathVariable int id) {
        return bookRepository.findById((long) id)
                             .orElse(null);
    }

    @GetMapping("/editBook/{id}")
    public void editBook(@PathVariable int id, @RequestParam String name, @RequestParam String genre) {
        Book book = getBookById(id);
        book.setGenre(genre);
        book.setName(name);
        bookRepository.save(book);
    }
}