Question

用于下载的弹簧控制器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;
}

但一般情况下，我看到控制器的void返回类型看起来像下面那个

    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.
    }
}

我在这里有两个问题：

a）他们的一种方法的缺点是否超过其他方法。我看到第一个用例比第二个更多。

b）返回null而不是ModelAndView是否有任何缺点。

参考文献：

Downloading a file from spring controllers

Error handling by redirection in spring download file controller

Answer 1

标记方法为void没什么不好的。您正在通过HttpServletResponse处理下载操作。有人建议FileSystemResource更清洁但考虑到例如在某些情况下，您需要将数据转发到其他地方，以便在其他地方撰写报告。

同样 Spring 可让您轻松处理异常，即使控制器中的返回类型为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扮演其角色：

@ControllerAdvice
public class ExceptionControllerAdvice {

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

来自Spring resources

的更多信息

Spring文件下载控制器中返回类型的意义

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