//servlet下载：根据请求url。拦截路径，读取服务器文件流，返回给浏览器，

 // 其中请求url可以通过request对象的getRequestURI()获取文件名（用来重命名文件）

public class DownloadServlet extends HttpServlet

{

 @Override

 protected void doGet(HttpServletRequest req, HttpServletResponse resp)

   throws ServletException, IOException

 {

  doPost(req, resp);

 }

 @Override

 protected void doPost(HttpServletRequest req, HttpServletResponse resp)

   throws ServletException, IOException

 {

  String url = req.getRequestURI();

  String resFileName = url.substring(url.lastIndexOf("/")+1,url.length());

  String realPath = req.getRealPath("/");

  String exeFile = realPath + "download/test.exe";

  String kipFile = realPath + "download/exe";

  PrintWriter out = resp.getWriter();

  if (Tools.checkFileExist(exeFile, kipFile))

  {

   try

   {

    File f = new File(exeFile);

    BufferedInputStream buffer = new BufferedInputStream(

      new FileInputStream(f));

    byte[] bt = new byte[1024];

    int len = 0;

    resp.reset();

    resp.setContentType("application/x-msdownload");

    resp.setHeader("Content-Disposition", "attachment;filename="

      + resFileName);

    OutputStream out1 = resp.getOutputStream();

    while ((len = buffer.read(bt)) > 0)

    {

     out1.write(bt, 0, len);

    }

    buffer.close();

    out1.close();

                                

   } catch (Exception e)

   {

    System.out.println("read downloadfile error:" + e);

   }

  } else

  {

   out.println("<center>file is not exsit!</center>");

  }

 }

}