struts 文件下载

以下代码是struts1中的action中
一般下载有三种方式,我常用的是这两种,做个记录

String dlpath = request.getParameter("dlpath");//文件相对路径
        if(dlpath == null || "".equals(dlpath.trim())){
        return null;
        }
       
        //得到下载文件名
        //可能还会查询数据库中当初保存时的名字
        String fileName = "";
        if(dlpath.lastIndexOf("/") > 0) {
        fileName = new String(dlpath.substring(dlpath.lastIndexOf("/")+1, dlpath.length()).getBytes("GB2312"), "ISO8859_1");
        }else if(dlpath.lastIndexOf("\\") > 0) {
        fileName = new String(dlpath.substring(dlpath.lastIndexOf("\\")+1, dlpath.length()).getBytes("GB2312"), "ISO8859_1");
        }

        response.reset();
        response.setContentType("application/x-msdownload");
response.setHeader("Content-Disposition", "attachment; filename=\""+fileName + "\"");

//=================第一种,相对最简单=====================
        RequestDispatcher dispatcher = request.getRequestDispatcher(dlpath);    
        if(dispatcher != null){    
            dispatcher.forward(request,response);    
        }    
        response.flushBuffer();
//=================/第一种===============================      

//=================第二种,输入/出流方式=====================
//            File uploadFile = new File(request.getSession().getServletContext().getRealPath(dlpath));
//            InputStream is = new FileInputStream(uploadFile);
//            BufferedInputStream bis = new BufferedInputStream(is);
//            OutputStream os = response.getOutputStream();
//            BufferedOutputStream bos = new BufferedOutputStream(os);
//               
//            int bytesRead = 0;
//            byte[] buffer = new byte[2048];
//            while((bytesRead = bis.read(buffer,0,2048)) != -1){
//                bos.write(buffer, 0, bytesRead);
//            }
//            bos.flush();
//            is.close();
//            bis.close();
//            os.close();
//            bos.close();
//==================/第二种============================================       
        return null ;


注意:
dlpath要以/开头,dispatcher才正确
response的设置和流的关闭,在struts action里的话,一定最后要返回null,因为在第一种方法里,dispatcher.forward后,不返回null,框架再返回就会出错,response已关闭