关于springmvc 文件下载，nginx 转发去掉了content-length ,浏览器前端下载没有进度，无法显示文件总大小的问题。

若要前端、浏览器显示下载进度，就必须直到问价总大小，要直到文件总大小就必须后端在响应头中加上content-length 即文件总大小。

Content-Length:byte大小

若响应有content-length时，浏览器会显示文件大小，如：

若响应没有content-length时，浏览器只会显示下载多少：

java下载代码

 1 /**
 2      * 下载/导出本地文件
 3      *
 4      * @author:
 5      * @param request
 6      * @param response
 7      * @param fileBytesLength 数据
 8      * @param fileLocalPath
 9      * @param responseContentType
10      * @param downFileName
11      * @throws Exception
12      */
13     public static void download(HttpServletRequest request, HttpServletResponse response,
14             String fileLocalPath,String responseContentType, String downFileName) throws Exception {
15         response.setContentType("text/html;charset=UTF-8");
16         request.setCharacterEncoding("UTF-8");
17         BufferedInputStream bis = null;
18         BufferedOutputStream bos = null;
19         File file=new File(fileLocalPath);
20         long fileLength = file.length();
21         response.setContentType(responseContentType);
22         response.setHeader("Content-disposition",
23                 "attachment; filename=" + new String(downFileName.getBytes("utf-8"), "ISO8859-1"));
24         response.setHeader("Content-Length", String.valueOf(fileLength));
25         bis = new BufferedInputStream(new FileInputStream(file));
26         bos = new BufferedOutputStream(response.getOutputStream());
27         byte[] buff = new byte[1024*10];
28         int bytesRead;
29         while (-1 != (bytesRead = bis.read(buff, 0, buff.length))) {
30             bos.write(buff, 0, bytesRead);
31         }
32         bis.close();
33         bos.close();
34     }