将错误消息下载或重定向到Spring Web MVC中的另一个控制器操作

Question

想法:我有一个Spring Web MVC动作应该完成其中一个或两个:

• 从远程服务器下载文件,并将输入流写入响应输出流
• 或者捕获下载的异常,设置多个错误消息之一并重定向到/ addresses页面.地址页面将显示错误

问题:Spring无法下载文件并在出现问题时重定向 - 某种方式flash属性不起作用,因为重定向中丢失了:

@ResponseBody
@RequestMapping(value = "/download/{fileaddress}", method = RequestMethod.GET)
public void download(HttpServletRequest request, HttpServletResponse response, @PathVariable(value = "fileaddress") String fileaddress) throws Exception
{
    if(fileaddress != null && fileaddress.length() > 0)
    {
        try
        {
            // Get the remove file based on the fileaddress
            RemoteFile remotefile = new RemoteFile(fileaddress);

            // Set the input stream
            InputStream inputstream = remotefile.getInputStream();

            // Write the input stream to the output stream or throw an exception
            Utils.writeTo(inputstream, response.getOutputStream());
        }
        catch(MyExceptionA)
        {
            // TODO: Define error message a and pass it to /addresses
            // PROBLEM: Flash attributes that contain all critical error information don't work
            response.sendRedirect(request.getContextPath() + "/addresses");
        }
        catch(MyExceptionB)
        {
            // TODO: Add another error message and redirect
            response.sendRedirect(request.getContextPath() + "/addresses");
        }
        catch(MyExceptionC)
        {
            // TODO: Add another error message and redirect
            response.sendRedirect(request.getContextPath() + "/addresses");
        }
        catch(MyExceptionN)
        {
            // TODO: Add another error message and redirect
            response.sendRedirect(request.getContextPath() + "/addresses");
        }
    }
    else
    {
        // TODO: Add error message
        response.sendRedirect(request.getContextPath() + "/addresses");
    }
}

JSP页面/地址:

<%@ page pageEncoding="UTF-8" %>
<%@ taglib prefix="tags" tagdir="/WEB-INF/tags" %>
<%@ taglib prefix="core" uri="http://java.sun.com/jsp/jstl/core" %>

<tags:index>
    <jsp:attribute name="content">
        <core:if test="${not empty error}">
            <div class="alert alert-danger">
                <p>${error}</p>
            </div>
        </core:if>
        <p>Page under construction!</p>
    </jsp:attribute>
</tags:index>

问题:我如何在/ addresses站点中显示错误消息(例如,简单字符串)？使用不同的URL参数(error = errora,error = errorb ...)是一个巨大的痛苦,如果有多种错误类型并传递错误消息,因为GET参数看起来不专业并且是编码问题的根源.

Answer 1

你需要什么RedirectAttributes的一个特例Model,其控制器可以用它来选择重定向场景的属性.所以对于一个工作示例,请参阅以下代码

@ResponseBody
@RequestMapping(value = "/download/{fileaddress}", method = RequestMethod.GET)
public Object download(@PathVariable(value = "fileaddress") String fileaddress, RedirectAttributes redirectAttrs) throws Exception {
    if(StringUtils.hasText(fileaddress)){
        try{
            // Get the remove file based on the fileaddress
            RemoteFile remotefile = new RemoteFile(fileaddress);

            // Set the input stream
            InputStream inputstream = remotefile.getInputStream();
            // asume that it was a PDF file
            HttpHeaders responseHeaders = new HttpHeaders();
            InputStreamResource inputStreamResource = new InputStreamResource(inputStream);
            responseHeaders.setContentLength(contentLengthOfStream);
            responseHeaders.setContentType(MediaType.valueOf("application/pdf"));
            return new ResponseEntity<InputStreamResource> (inputStreamResource,
                                       responseHeaders,
                                       HttpStatus.OK);
         } catch (MyExceptionA | MyExceptionB | MyExceptionC | MyExceptionD ex) {
           redirectAttrs.addFlashAttribute("error", ex.getMessage());
         }        
    } else {
        redirectAttrs.addFlashAttribute("error", "File name is required");
    }
    return "redirect:/addresses";
}