1 public void fileDownload(HttpServletResponse response){  
 2         //获取网站部署路径(通过ServletContext对象)，用于确定下载文件位置，从而实现下载  
 3         String path = servletContext.getRealPath("/");  
 4   
 5         //1.设置文件ContentType类型，这样设置，会自动判断下载文件类型  
 6         response.setContentType("multipart/form-data");  
 7         //2.设置文件头：最后一个参数是设置下载文件名(假如我们叫a.pdf)  
 8         response.setHeader("Content-Disposition", "attachment;fileName="+"a.pdf");  
 9         ServletOutputStream out;  
10         //通过文件路径获得File对象(假如此路径中有一个download.pdf文件)  
11         File file = new File(path + "download/" + "download.pdf");  
12   
13         try {  
14             FileInputStream inputStream = new FileInputStream(file);  
15   
16             //3.通过response获取ServletOutputStream对象(out)  
17             out = response.getOutputStream();  
18   
19             int b = 0;  
20             byte[] buffer = new byte[512];  
21             while (b != -1){  
22                 b = inputStream.read(buffer);  
23                 //4.写到输出流(out)中  
24                 out.write(buffer,0,b);  
25             }  
26             inputStream.close();  
27             out.close();  
28             out.flush();  
29   
30         } catch (IOException e) {  
31             e.printStackTrace();  
32         }  
33     }