java - spring文件下载 Controller 中返回类型的意义

Question

用于下载的 Spring Controller 中返回类型的意义是什么。请考虑以下用例:

public ModelAndView execute(final HttpServletRequest request, final HttpServletResponse response) {
    try {
        //some code.
    } catch {
        //handle the exception and build a error model and view. This model and view
        //gives a lot of freedom for error handling in case of download fails on the
        //same page without change in URL(enabling refresh of the same page again 
        //and again)
        return modelAndView;
    }
    return null;
}

但通常我见过具有 void 返回类型的 Controller ，如下所示

    public void execute(final HttpServletRequest request, final HttpServletResponse response) {
    try {
        //some code.
    } catch {
        //handle the exception but you cannot display the error with out leaving the same page. Error embedding is not possible without changing the URL.
    }
}

我有两个问题:

a) 一种方法相对于另一种方法的缺点是什么？我发现第一个服务的用例比第二个多。

b)返回 null 而不是 ModelAndView 有什么缺点吗？

引用资料:

Downloading a file from spring controllers

Error handling by redirection in spring download file controller

Answer 1

将方法标记为 void 没什么不好。您正在通过 HttpServletResponse 处理下载操作。有人建议 FileSystemResource 更干净，但要考虑到这一点，例如在某些情况下，您需要将数据转发到其他地方，以便在其他地方撰写报告。

此外，Spring 让您轻松处理异常，即使您在 Controller 中的返回类型是 void:

@RequestMapping(value = "/pdf-report/{id}.pdf", method = RequestMethod.GET)
public void downloadPdfReport(@PathVariable String id, HttpServletRequest req, HttpServletResponse resp) throws Exception {

    //supposed logic here
    //if we are failing here then
    throw new UserFriendlyException("Cannot produce data");
}

然后 ControllerAdvice 发挥作用:

@ControllerAdvice
public class ExceptionControllerAdvice {

    @ExceptionHandler(UserFriendlyException.class)
    public ModelAndView handleUserFriendlyException(UserFriendlyException ex) {
        //handle here your custom error page
    }
}

更多信息来自 Spring resources