用Jsp来实现文件下载功能的几种方式

public void service(HttpServletRequest req, HttpServletResponse res)

           throws ServletException, IOException {
        res.setContentType(" text/plain ");
        InputStream inputStream = null;
        try {
            inputStream = res.getInputStream();
//把输入流inputStream保存到文件路径为srcFile的文件中
            writefile(srcFile, inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    } // end service