从jsp页面检索多个模型属性（Spring）

Question

在ReservationController中。java我有以下方法，它从新的reservation中获取reservation对象。jsp

    @PostMapping("/addBookToReservation")
    public String addBookToReservation(Model model,
                                      @Valid @ModelAttribute("reservation") Reservation reservation,
                                      BindingResult result,
                                      RedirectAttributes redirectAttributes) {
        
        if(result.hasErrors()) {
            return "reservation/new-reservation";
        }
    
        redirectAttributes.addFlashAttribute("reservation", reservation);
        
        return "redirect:/book/add-book";
    }

并将其发送到BookController。java，其中另一个方法向模型添加另一个属性

    @GetMapping("/book/add-book")
    public String showAddBookForm(Model model) {

        model.addAttribute("book", new Book());
        Reservation reservation = (Reservation) model.getAttribute("reservation");
        System.out.println(reservation);       //prints the object I passed it!

        return "/book/add-book";
    }

并返回以下addbook。jsp

<form:form action="/addBook" modelAttribute="book" method="post">                    
   <div>
        <div>
            <form:label path="title">Title</form:label>
            <form:input type="text" id="title" path="title" />
            <form:errors path="title" />
        </div>
        ...
    </div>
    <div>
        <input type="submit" value="Add book">
    </div>
</form:form>

现在，当我处理表单的action addBook时

    @PostMapping("/addBook")
    public String addBook(@Valid @ModelAttribute Book book,
                            BindingResult result,
                            Model model) {
        
        if (result.hasErrors()) {
            return "book/add-book";
        }
        
        Reservation reservation = (Reservation) model.getAttribute("reservation");
        System.out.println(reservation); // reservation is null!!
        
        
        return "somewhere/else";
    } 

我试图从模型中检索保留对象，但得到一个空。我如何通过我之前向您展示过的JSP传递我的预订对象？

Answer 1

尝试在控制器顶部添加模型属性的@SessionAttributes，并在完成后删除会话属性

@SessionAttributes("reservation")