java下载文件

public void downloadTmp(HttpServletRequest request,HttpServletResponse response){
        try {
            request.setCharacterEncoding("UTF-8"); 5             //第一步：设置响应类型
            response.setContentType("application/force-download");//应用程序强制下载
            //第二读取文件
            String path = request.getServletContext().getRealPath(File.separator+"source"+File.separator+"tmp.txt");
            InputStream in = new FileInputStream(path);
            //设置响应头，对文件进行url编码
            //name = URLEncoder.encode(name, "UTF-8");
            response.setHeader("Content-Disposition", "attachment;filename=tmp.txt");
            response.setContentLength(in.available());

            OutputStream out = response.getOutputStream();
            byte[] b = new byte[1024];
            int len = 0;
            while((len = in.read(b))!=-1){
                out.write(b, 0, len);
            }
            out.flush();
            out.close();
            in.close();
        }catch (Exception e){
            e.printStackTrace();
        }
    }