form.add(new TextField("publicationYear", new PropertyModel<String>(book, "publicationYear")).setRequired(true));
form.add(new TextField( "publicationPlace", new PropertyModel<String>(book, "publicationPlace")).setRequired(true));
form.add(new TextField("publisher", new PropertyModel<String>(book, "publisher")).setRequired(true));
form.add(new TextField("ISBN", new PropertyModel<String>(book, "ISBN")).setRequired(true));
BookmarkablePageLink books = new BookmarkablePageLink<>(
"list", ShowAllBook.class);
add(books);
}