Spring Boot redirectAttributes.addFlashAttribute不保留立即重定向中的值

问题描述

我有一个实现GET-POST-GET重定向模式的控制器类.我试图在POST请求中使用addFlashAttribute并将其重定向到GET，但是GET中的模型对象不包含设置值.这是我的代码:

I have a controller class which implements GET-POST-GET redirect pattern. I have tried to use addFlashAttribute in the POST request and redirecting to GET but the model object in GET does not contain the set value. Here is my code:

@Controller
@RequestMapping("/eg")
public class Example extends AbstractBaseController {

@RequestMapping(value = "/account", method = RequestMethod.GET)
public String renderFavouriteView(
        HttpServletRequest request,
        HttpServletResponse response,
        ExtendedModelMap modelMap,
        @ModelAttribute("result") String postResult) {


    modelMap.addAttribute("result", postResult); //postResult is empty

    return "account.ftl";
}

@RequestMapping(value = "/account", method = RequestMethod.POST)
public String handleFavouriteView(
        AccountForm accountForm,
        HttpServletRequest request,
        HttpServletResponse response,
        ExtendedModelMap modelMap,
        RedirectAttributes redirectAttributes) {

    ServiceResult serviceResult = myAccountService.createAccount(accountForm);

    if (!serviceResult.isSuccess()) {
        redirectAttributes.addFlashAttribute("result", "Done");
    } else {

        redirectAttributes.addFlashAttribute("result", "Failed");
    }

    Map<String,?> m = redirectAttributes.getFlashAttributes(); // present here.

    return "redirect:/eg/account";
}

}

如果我在这里丢失了一些东西，请告诉我.

Please let me know, if I am missing something here.

推荐答案

在PRG情况下使用 RedirectAttributes 时，您要做的只是:

When using RedirectAttributes in a PRG situation, all you need to do is:

1. 将 RedirectAttributes 作为POST方法签名的参数
2. 通过POST方法中的 addFlashAttribute 设置所需的属性
3. 在GET方法签名中包含一个@ModelAttribute注释的参数，该参数引用了flash属性

1. Include RedirectAttributes as parameter to the POST method signature
2. Set the attribute you want via addFlashAttribute within the POST method
3. Include a @ModelAttribute annotated parameter in the GET method signature which references the flash attribute

所以您真的不需要POST方法中的这一行:

So you really do not need this line from the POST method:

Map<String,?> m = redirectAttributes.getFlashAttributes(); // present here.

但是我认为您的实际问题是您无意中使用了以下行覆盖GET方法中的model属性:

modelMap.addAttribute("result", postResult); //postResult is empty

Flash属性已在重定向期间自动添加到模型中，因此上面的行实际上覆盖了它.如果您删除该行，它应该可以正常工作.

Flash attributes are already automatically added to the model during the redirection, so above line is actually overwriting it. If you remove that line it should work as intended.

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