Nie mogę dodać obiektu do bazy danych

Question

Cześć,

Potrzebuję wasze pomocy. Piszę właśnie aplikacje internetowej biblioteki za pomocą Spring Boot + thymeleaf. W związku z tym, że pomiędzy ksiażkami a autorami w bazie danych zachodzi relacja @Manytomany nie potrafię poradzić sobie z dodanie nowej ksiażki za pomocą formularza html. Czy ktoś mógłby mi podpowiedzieć jak to należy zrobić. Na dole wysyłam mój kod.

import javax.persistence.*;
import java.util.List;
import java.util.Objects;

@Entity
@Table(name = "book")
public class Book {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id")
    private Integer id;
    @Column(name = "title")
    private String title;
    @Column(name = "year")
    private Integer year;

    @ManyToMany(cascade = {CascadeType.DETACH, CascadeType.MERGE,
            CascadeType.PERSIST, CascadeType.REFRESH})
    @JoinTable(
            name = "books_authors",
            joinColumns = @JoinColumn(name = "book_id", unique = false),
            inverseJoinColumns = @JoinColumn(name = "author_id", unique = false)
    )
    private List<Author> authors;

    //konstruktory, gettery/settery toString()

}

 

import javax.persistence.*;
import java.util.List;

@Entity
@Table(name = "author")
public class Author {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id")
    private Integer id;
    @Column(name = "name")
    private String name;


    @ManyToMany(cascade = {CascadeType.DETACH, CascadeType.MERGE,
            CascadeType.PERSIST, CascadeType.REFRESH})
    @JoinTable(
            name = "books_authors",
            joinColumns = @JoinColumn(name = "author_id", unique = false),
            inverseJoinColumns = @JoinColumn(name = "book_id", unique = false)
    )
    private List<Book> books;

   //konstruktory gettery/settery toString()

}

 

import com.example.myTestProject.entity.Author;
import org.springframework.data.jpa.repository.JpaRepository;

public interface AuthorRepository extends JpaRepository<Author, Integer> {
}



import com.example.myTestProject.entity.Book;
import org.springframework.data.jpa.repository.JpaRepository;

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

 

mport com.example.myTestProject.entity.Book;

import java.util.List;
import java.util.Optional;

public interface BookService {

    public List<Book> findAll();

    public Optional<Book> findById(int theId);

    public void save(Book theBook);

    public void deleteById(int theId);
}




import com.example.myTestProject.dao.BookRepository;
import com.example.myTestProject.entity.Book;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;
import java.util.Optional;

@Service
public class BookServiceImpl implements BookService {

    private BookRepository bookRepository;

    @Autowired
    public BookServiceImpl(BookRepository theBookRepository){
        bookRepository = theBookRepository;
    }

    @Override
    public List<Book> findAll() {
        return bookRepository.findAll();
    }

    @Override
    public Optional<Book> findById(int theId) {

        Optional<Book> book = bookRepository.findById(theId);

        if (book.isEmpty()){
            throw new RuntimeException("Didn't find book id - " + theId);
        }
        else {
            return book;
        }
    }

    @Override
    public void save(Book theBook) {
        bookRepository.save(theBook);
    }

    @Override
    public void deleteById(int theId) {
        bookRepository.deleteById(theId);
    }
}

 

import com.example.myTestProject.entity.Book;
import com.example.myTestProject.service.BookService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;

import java.util.List;

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

    private BookService bookService;

    @Autowired
    public BookController(BookService theBookService){
        bookService = theBookService;
    }

    @GetMapping("/list")
    public String listBooks(Model theModel){
        List<Book> theBooks = bookService.findAll();

        //add to the spring model
        theModel.addAttribute("books", theBooks);

        return"books/list-books";
    }

    @GetMapping("/showFormForAdd")
    public String showFormForAdd(Model theModel) {

        // create model attribute to bind form data
        Book theBook = new Book();

        theModel.addAttribute("book", theBook);

        return "books/book-form";
    }

    @PostMapping("/save")
    public String saveBook(@ModelAttribute("book") Book theBook){

        //save the book
        bookService.save(theBook);

        //use a ridirect to prevent duplicate submissions
        return "redirect:/book/list";
    }
}

 

<!DOCTYPE HTML>
<html lang="en" xmlns:th="http://www.thymeleaf.org">

<head>
  <!-- Required meta tags -->
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">

  <!-- Bootstrap CSS -->
  <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.2.1/css/bootstrap.min.css" integrity="sha384-GJzZqFGwb1QTTN6wy59ffF1BuGJpLSa9DkKMp0DgiMDm4iYMj70gZWKYbI706tWS" crossorigin="anonymous">

  <title>Books</title>
</head>

<body>

<div class="container">

  <h3>Books</h3>
  <hr>

  <!-- Add a button -->
  <a th:href="@{/books/showFormForAdd}"
     class="btn btn-primary btn-sm mb-3">
    Add Book
  </a>

  <table class="table table-bordered table-striped">
    <thead class="thead-dark">
    <tr>
      <th>Title</th>
      <th>Year</th>
      <th>Author</th>
    </tr>
    </thead>

    <tbody>
    <tr th:each="tempBook : ${books}">

      <td th:text="${tempBook.title}" />
      <td th:text="${tempBook.year}" />
      <td th:text="${tempBook.authors}" />

    </tr>
    </tbody>
  </table>
</div>
</body>
</html>

 

<!DOCTYPE HTML>
<html lang="en" xmlns:th="http://www.thymeleaf.org">

<head>
  <!-- Required meta tags -->
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">

  <!-- Bootstrap CSS -->
  <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.2.1/css/bootstrap.min.css" integrity="sha384-GJzZqFGwb1QTTN6wy59ffF1BuGJpLSa9DkKMp0DgiMDm4iYMj70gZWKYbI706tWS" crossorigin="anonymous">

  <title>Save Book</title>
</head>
<body>
  <div class="container">

    <h3>Book Directory</h3>
    <hr>

    <p class="h4 mb-4">Save Book</p>

    <form action="#" th:action="@{/books/save}"
                      th:object="${book}" method="post">

      <input type="text" th:field="*{title}"
              class="form-control mb-4 col-4" placeholder="Title">

      <input type="text" th:field="*{year}"
             class="form-control mb-4 col-4" placeholder="Year">

      <input type="text" th:field="*{authors}"
             class="form-control mb-4 col-4" placeholder="author">

      <button type="submit" class="btn btn-info col-2">Save</button>

    </form>

    <hr>
    <a th:href="@{/books/list}">Back to Employees List</a>

  </div>
</body>
</html>

 

Z góry dziękuję za wszystkie podpowiedzi :)