Question

您已经编写了如下控制器类。我试图从mongo db获取文件并尝试下载它。

    organizationFileAttachmentService.setUser(getUser());
    GridFSDBFile file = organizationFileAttachmentService.getGridFSDBFileById(new ObjectId(id), "File");
    if (file != null) {
        byte[] content = organizationFileAttachmentService.findByIdAndBucket(new ObjectId(id), "File");
        try {
            int size = content.length;
            InputStream is = null;
            byte[] b = new byte[size];
            try {
                is = new ByteArrayInputStream(content);
                is.read(b);
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                try {
                    if (is != null)
                        is.close();
                } catch (Exception ex) {

                }
            }
            response.setContentType(file.getContentType());
            // String attachment =
            // "attachment; filename=\""+file.getFilename()+"\"";
            String attachment = "attachment; filename=" + file.getFilename();
            // response.setContentLength(new
            // Long(file.getLength()).intValue());
            response.setCharacterEncoding(file.getMD5());
            response.setHeader("content-Disposition", attachment);// "attachment;filename=test.xls"
            // copy it to response's OutputStream
            // FileCopyUtils.copy(is, response.getOutputStream());
            IOUtils.copy(is, response.getOutputStream());
            response.flushBuffer();
            is.close();
        } catch (IOException ex) {
            _logger.info("Error writing file to output stream. Filename was '" + id + "'");
            throw new RuntimeException("IOError writing file to output stream");
        }

但我无法下载文件。任何人都可以帮助我。

Answer 1

如果您错过了它，Spring会提供各种内置资源处理程序。

http://docs.spring.io/spring/docs/3.2.5.RELEASE/spring-framework-reference/html/resources.html#resources-implementations

如果你的方法返回其中一个（在你的情况下可能是ByteArrayResource），那么你只需要在界面上添加几个注释：

@RequestMapping(value = "/foo/bar/{fileId}", 
    method = RequestMethod.GET, 
    produces = { MediaType.APPLICATION_OCTET_STREAM_VALUE })
@ResponseBody FileSystemResource downloadFile(Long fileId);

不要以这种方式摆弄编码和标题。我推荐在推出自己之前尝试一下。

编辑：以上在Spring 3.1.4中运行良好。它不再适用于3.2.x或4.x.而以前，produce = {MediaType.APPLICATION_OCTET_STREAM_VALUE}会导致Spring添加适当的标头，现在它将其视为限制。如果使用标准Web浏览器访问URL，则不会发送“application / octet-stream”的接受标头。因此Spring将返回406错误。为了让它再次工作，需要重写这种方法而不使用“produce”属性。相反，将HttpServletResponse添加到方法参数并在方法内添加标头。即：

@RequestMapping(value = "/foo/bar/{fileId}", 
    method = RequestMethod.GET)
@ResponseBody FileSystemResource downloadFile(
            Long fileId, HttpServletResponse response) {
    ...
    response.setHeader( "Content-Disposition", "attachment;filename=" + fileName );
    ...
}

编辑redux：现在通过Spring Boot 1.1.8使用Spring 4.0.7。似乎设置produces = { MediaType.APPLICATION_OCTET_STREAM_VALUE }指令现在再次起作用。对于我尝试过的所有浏览器来说，只是拥有该指令似乎已经足够了。但请注意，我还发现它没有设置Content-Disposition，而是application/json。虽然这似乎不是浏览器的问题，但我遇到了PHP客户端应用程序中的错误，它们似乎只基于Content-Disposition。因此，目前的解决方案似乎是要做到上述两点！

Answer 2

我已将我的请求更改为GET，并在html中的锚标记中添加了请求。 Aslo将我的代码更改为

@RequestMapping(value = "/getFileById/{id}", method = RequestMethod.GET)
public @ResponseBody
void download(@PathVariable String id, HttpServletRequest request, HttpServletResponse response) throws IOException {
    organizationFileAttachmentService.setUser(getUser());
    GridFSDBFile file = organizationFileAttachmentService.getGridFSDBFileById(new ObjectId(id), "File");
    if (file != null) {
        try {
            response.setContentType(file.getContentType());
            response.setContentLength((new Long(file.getLength()).intValue()));
            response.setHeader("content-Disposition", "attachment; filename=" + file.getFilename());// "attachment;filename=test.xls"
            // copy it to response's OutputStream
            IOUtils.copyLarge(file.getInputStream(), response.getOutputStream());
        } catch (IOException ex) {
            _logger.info("Error writing file to output stream. Filename was '" + id + "'");
            throw new RuntimeException("IOError writing file to output stream");
        }
    }
}

现在它对我来说很好。

如何在Spring mvc和mongodb中下载文件

2 个答案: