就是自己写的下载代码
String filename = this.getFilename();
             ServletActionContext.getResponse().addHeader("Content-Disposition",
             "attachment; filename=" + filename);
            String filetype = ServletActionContext.getServletContext()
                                                  .getMimeType(filename);
            ServletActionContext.getResponse().setContentType(filetype);
            
            BufferedInputStream input = null;
            BufferedOutputStream output = null;            try {
                input = new BufferedInputStream(inputStream);
                output = new BufferedOutputStream(ServletActionContext.getResponse()
                                                                      .getOutputStream());
                int bufsize=4096;
                byte[] buf=new byte[bufsize];
                int cnt=0;
                while((cnt=input.read(buf))>=0)
                 output.write(buf);
}