@RequestMapping("/courseware/{id}")
public void download(@PathVariable("id") String courseID, HttpServletResponse response) throws Exception {
ResourceFile file = coursewareService.downCoursewareFile(courseID);
response.setContentType(file.getType());
response.setContentLength(file.contentLength());
response.setHeader("Content-Disposition","attachment; filename=\"" + file.getFilename() +"\"");
//Reade File - > Write To response
FileCopyUtils.copy(file.getFile(), response.getOutputStream());
}
@RequestMapping("/courseware/{id}")
public void download(@PathVariable("id") String courseID, HttpServletResponse response) throws Exception {
ResourceFile file = coursewareService.downCoursewareFile(courseID);
response.setContentType(file.getType());
response.setContentLength(file.contentLength());
response.setHeader("Content-Disposition","attachment; filename=\"" + file.getFilename() +"\"");
//Reade File - > Write To response
FileCopyUtils.copy(file.getFile(), response.getOutputStream());
}
由于程序的IO都是调用系统底层IO进行文件操作，于是这种方式在read和write时系统都会进行两次内存拷贝(共四次)。linux 中引入的 sendfile 的实际就为了更好的解决这个问题，从而实现"零拷贝"，大大提升文件下载速度。
使用 sendfile() 提升网络文件发送性能
RoR网站如何利用lighttpd的X-sendfile功能提升文件下载性能
在apache，nginx，lighttpd等web服务器当中，都有sendfile feature。下面就对 nginx 上的XSendfile与SpringMVC文件下载及访问控制进行说明。我们这里的大体流程为：
1.用户发起下载课件请求； (http://dl.mydomain.com/download/courseware/1)
2.nginx截获到该(dl.mydomain.com)域名的请求;
3.将其proxy_pass至应用服务器；
4.应用服务器根据课件id获取文件存储路径等其它一些业务逻辑(如增加下载次数等)；
5.如果允许下载，则应用服务器通过setHeader -> X-Accel-Redirect 将需要下载的文件转发至nginx中)；
6.Nginx获取到header以sendfile方式从NFS读取文件并进行下载。
其nginx中的配置为：
在location中加入以下配置
server {
listen 80;
server_name dl.mydomain.com;
location / {
proxy_pass http://127.0.0.1:8080/; #首先pass到应用服务器
proxy_redirect off;
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
client_max_body_size 10m;
client_body_buffer_size 128k;
proxy_connect_timeout 90;
proxy_send_timeout 90;
proxy_read_timeout 90;
proxy_buffer_size 4k;
proxy_buffers 4 32k;
proxy_busy_buffers_size 64k;
proxy_temp_file_write_size 64k;
}
location /course/ {
charset utf-8;
alias /nfs/files/; #文件的根目录（允许使用本地磁盘，NFS，NAS，NBD等）
internal;
}
}
其Spring代码为：
package com.xxxx.portal.web;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import javax.servlet.http.HttpServletResponse;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import com.xxxx.core.io.ResourceFile;
import com.xxxx.portal.services.CoursewareService;
/**
* File download controller, provide courseware download or other files. <br>
* <br>
* <i> download a course URL e.g:<br>
* http://dl.mydomain.com/download/courseware/1 </i>
*
* @author denger
*/
@Controller
@RequestMapping("/download/*")
public class DownloadController {
private CoursewareService coursewareService;
protected static final String DEFAULT_FILE_ENCODING = "ISO-8859-1";
/**
* Under the courseware id to download the file.
*
* @param courseID The course id.
* @throws IOException
*/
@RequestMapping("/courseware/{id}")
public void downCourseware(@PathVariable("id") String courseID, final HttpServletResponse response) throws IOException {
ResourceFile file = coursewareService.downCoursewareFile(courseID);
if (file != null && file.exists()){
// redirect file to x-accel-Redirect
xAccelRedirectFile(file, response);
} else { // If not found resource file, send the 404 code
response.sendError(404);
}
}
protected void xAccelRedirectFile(ResourceFile file, HttpServletResponse response)
throws IOException {
String encoding = response.getCharacterEncoding();
response.setHeader("Content-Type", "application/octet-stream");
//这里获取到文件的相对路径。其中 /course/ 为虚拟路径，主要用于nginx中进行拦截包含了/course/ 的URL， 并进行文件下载。
//在以上nginx配置的第二个location 中同样也设置了 /course/，实际的文件下载路径并不会包含 /course/
//当然，如果希望包含的话可以将以上的 alias 改为 root 即可。
response.setHeader("X-Accel-Redirect", "/course/"
+ toPathEncoding(encoding, file.getRelativePath()));
response.setHeader("X-Accel-Charset", "utf-8");
response.setHeader("Content-Disposition", "attachment; filename="
+ toPathEncoding(encoding, file.getFilename()));
response.setContentLength((int) file.contentLength());
}
//如果存在中文文件名或中文路径需要对其进行编码成 iSO-8859-1
//否则会导致 nginx无法找到文件及弹出的文件下载框也会乱码
private String toPathEncoding(String origEncoding, String fileName) throws UnsupportedEncodingException{
return new String(fileName.getBytes(origEncoding), DEFAULT_FILE_ENCODING);
}
@Autowired
public void setCoursewareService(CoursewareService coursewareService) {
this.coursewareService = coursewareService;
}
}
