java之servlet之文件下载

@WebServlet("/download")
public class DownloadServlet extends HttpServlet{
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        resp.setCharacterEncoding("utf-8");
        resp.setContentType("application/octet-stream");
        //解决 以文件形式下载 而不会被浏览器打开    以及中文文件名需要编码
        resp.setHeader("Content-Disposition", "attachment;filename="+URLEncoder.encode("中国", "utf-8")+".txt");
        PrintWriter os = resp.getWriter();
        String path = this.getServletContext().getRealPath("/download");
        Reader is = new BufferedReader(new FileReader(new File(path,"t.txt")));
        int len=0;
        char[] buffer = new char[200];
        while((len=is.read(buffer))!=-1){
            os.print(new String(buffer,0,len));
        }
        is.close();
        os.close();
    }
}