基于Nginx XSendfile+SpringMVC进行文件下载

2018-12-15 13:38:10
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在平常我们实现文件下载通常是通过普通 read-write方式,如下代码所示。


@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。 


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;  
        }  
    }

Spring代码为: 


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;  
    }  
}



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