I am new to Spring and yesterday I created a simple app. I type book's title, author and genre and it saves it to List<Book>. Book.java contains private fields (title, author, genre).
So creating books and saving them to list works fine. Also I can view all books I have added. So it works fine. But now I want to create and delete them. So I have BookService.java that can add and delete books.
BookService.java
private List<Book> allBooks = new ArrayList<>();
public List<Book> getAllBooks() {
return allBooks;
}
public void addBook(String title, String author, String genre) {
allBooks.add(new Book(title, author, genre));
}
public void deleteBook(Book book) {
allBooks.remove(book);
}
This is stuff in my controller to delete books
@GetMapping("/books/delete")
public String deleteBook(Model model) {
model.addAttribute("BookList", bookService.getAllBooks()); // Works fine
return "delete";
}
@PostMapping("/books/delete")
public String deletedBook(@ModelAttribute Book book, Model model) {
System.out.println(book.getTitle()); // null
bookService.deleteBook(book); // can't delete null so nothing happens to the list
model.addAttribute("deletedBook", book);
return "deletedBookResult";
}
delete.html
<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
<meta charset="UTF-8"/>
<title>Title</title>
</head>
<body>
<h2>Delete page</h2>
<div th:each="bookObj : ${BookList}"> <!-- BookList - all books I add using submit form -->
<form action="#" th:action="@{/books/delete}" th:object="${bookObj}" method="post"> <!-- I SEND bookObj -->
<input type="submit" th:value="${bookObj.title}"/> <!-- WORKS. I GET BOOK'S NAME ON THIS BUTTON-->
</form>
</div>
</body>
</html>
I use th:each="bookObj : ${BookList}". So bookObj is every book I add. That's why I use th:object=${bookObj}. There is a form for each book I added later. And it display's it's title on the button. But when I press it, I get null to IDEA's console and on webpage. Why? Thank you in advance.
<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
<meta charset="UTF-8"/>
<title>Title</title>
</head>
<body>
<h2 th:text=" 'You have just deleted' + ${deletedBook.title}"></h2>
<!-- You have just deleted null -->
</body>
</html>
You are not sending anything in your form. Add some hidden fields:
<div th:each="bookObj : ${BookList}">
<form action="#" th:action="@{/books/delete}" method="post">
<input type="hidden" th:name="genre" th:value="${bookObj.genre}"/>
<input type="hidden" th:name="author" th:value="${bookObj.author}"/>
<input type="hidden" th:name="title" th:value="${bookObj.title}"/>
<input type="submit" th:value="${bookObj.title}"/>
</form>
</div>
Or if you don't want to expose your data in html, you can try to use some sort of session objects instead (Probably an overkill, but sometimes can be useful):
@GetMapping("/books/delete")
public String deleteBook(Model model, HttpSession session) {
session.setAttribute("BookList", new Book[]{
new Book("Title", "Tom","genre"),
new Book("Title 2", "Jerry","genre2")}
);
return "delete";
}
@PostMapping("/books/delete")
public String deletedBook(HttpSession session, Integer id, Model model) {
Book[] books = (Book[]) session.getAttribute("BookList");
Book book = books[id];
System.out.println(book);
model.addAttribute("deletedBook", book);
return "deletedBookResult";
}
And use it like:
<div th:each="bookObj, iter : ${session.BookList}">
<form action="#" th:action="@{/books/delete}" method="post">
<input type="hidden" th:name="id" th:value="${iter.index}"/>
<input type="submit" th:value="${bookObj.title}"/>
</form>
</div>
Collected from the Internet
Please contact [email protected] to delete if infringement.
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