流下载

 private ActionForward doExportPrefixData(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response)
    {
        String fileName=request.getParameter("fileName"); //页面传来的文件名
        String filePath=ServerInfo.getDownloadPath()+fileName;//路径+文件名
        try
        {
            InputStream in=new FileInputStream(new File(filePath));
            BufferedInputStream bfin=new BufferedInputStream(in);
            response.setBufferSize(5*1024*1024);//5M大小
            response.setContentType("APPLICATION/OCTET-STREAM");
            response.setHeader("Content-Disposition","attachment;filename="+fileName);//设置文件头
            OutputStream out=response.getOutputStream();
            BufferedOutputStream bfout=new BufferedOutputStream(out);
            int len=0;
            byte[] b=new byte[1024*1024];
            while((len=bfin.read(b))!=-1)
            {
                bfout.write(b, 0, len);
                bfout.flush();
            }            
            bfout.close();
            out.close();
            bfin.close();
            in.close();
        }
        catch (FileNotFoundException e)
        {            
            showInfoDialog(response,"文件没找到");
        }
        catch (IOException e)
        {
            showInfoDialog(response,"文件读取失败");
        }
        return null;
    }
/**
     * 
     * 方法描述：公用的弹出提示框
     * @param response
     * @param msg 要提示的消息
     */
    private void showInfoDialog(HttpServletResponse response,String msg)
    {
        try
        {
            response.setContentType("text/html;charset=gb2312");
            PrintWriter pw=response.getWriter();   
            pw.print("<script>");
            pw.print("alert('"+msg+"');window.close();");
            pw.print("</script>");                
            pw.flush();
            pw.close();            
        }
        catch (IOException e1)
        {                
            e1.printStackTrace();
        }
    }