所以实际上我有一个控制器，显示表单给用户。用户得到的表单，例如，如果他输入了错误的数据，例如金额字段只是正数，但用户插入-1用户将在屏幕上得到错误消息，但当用户改变该值，并输入例如3金额和提交表单，用户得到404 Whitelabel Error Page。
第一个网址是：
http://localhost:8080/api/transaction/expenseTransaction/4，现在，用户输入金额-1并单击提交，URL为http://localhost:8080/api/transaction/saveExpense/4，因此，是否有任何方法可以停留在同一页面上，并允许用户在正确插入数据后保存表单？
我有这个控制器显示窗体：

@GetMapping("/expenseTransaction/{id}")
public String expenseTransaction(@PathVariable(value = "id") long id, Transaction transaction, Model model) {
    Authentication authentication = SecurityContextHolder.getContext().getAuthentication();
    UserDetailsImpl user = (UserDetailsImpl) authentication.getPrincipal();
    long userId = user.getId();
    model.addAttribute("userId", userId);

    model.addAttribute("transaction", transaction);
    model.addAttribute("expenseCategories", ExpenseCategories.values());

    return "expense_transaction";

}

这是一种形式：

<div class="container my-5">
<h3> Expense transaction</h3>
<div class="card">
    <div class="card-body">
        <div class="col-md-8">
            <form action="#"
                  th:action="@{/api/transaction/saveExpense/{walletId} (walletId=${id})}"
                  th:object="${transaction}" method="post">
                <div class="row">
                    <div class="form-group col-md-6">
                        <label for="amount" class="col-form-label">Amount</label> <input
                            type="text" th:field="*{amount}" class="form-control" id="amount"
                            placeholder="amount"> <span
                            th:if="${#fields.hasErrors('amount')}" th:errors="*{amount}"
                            class="text-danger"></span>
                    </div>
                    <div class="form-group col-md-8">
                        <label for="note" class="col-form-label">Note</label> <input
                            type="text" th:field="*{note}" class="form-control" id="note"
                            placeholder="note"> <span
                            th:if="${#fields.hasErrors('note')}" th:errors="*{note}"
                            class="text-danger"></span>
                    </div>
                    <div class="form-group col-md-8">
                        <label for="date" class="col-form-label">Date</label> <input
                            type="date" th:field="*{date}" class="form-control"
                            id="date" placeholder="date"> <span
                            th:if="${#fields.hasErrors('date')}" th:errors="date"
                            class="text-danger"></span>
                    </div>
                    <div class="form-group col-md-8">
                        <label for="date" class="col-form-label">Category</label>
                        <select th:field="${transaction.expenseCategories}">
                            <option value="0">Select expense category</option>
                            <option
                                    th:each="expenseCategories : ${expenseCategories}"
                                    th:value="${expenseCategories}"
                                    th:text="${expenseCategories.displayName}"
                            ></option>
                        </select>
                    </div>

                    <div class="form-group col-md-8">
                        <input type="submit" class="btn btn-primary"
                               value="Update Student">
                    </div>
                </div>
            </form>
        </div>
    </div>
</div>

这是保存该表单的控制器：

@PostMapping("/saveExpense/{walletId}")
public String saveExpense(@PathVariable(value = "walletId") long walletId,
                          @Valid Transaction transaction, BindingResult result, Model model) {

    Authentication authentication = SecurityContextHolder.getContext().getAuthentication();
    UserDetailsImpl user = (UserDetailsImpl) authentication.getPrincipal();
    long userId = user.getId();

    Wallet wallet = walletService.getWalletById(walletId);

    boolean thereAreErrors = result.hasErrors();
    if (thereAreErrors) {
        transaction.setId(walletId);
        model.addAttribute("expenseCategories", ExpenseCategories.values());
        return "expense_transaction";
    }

    transaction.setWallet(wallet);
    transactionService.saveExpense(transaction, walletId, userId);
    return "redirect:/api/wallet/userWallet/balance/" + userId;

}