struts上传文件如何限制大小

upload = FileUpload.fileUpload(file, file_save_name, prefix,"manyPicture");if (!upload) {
request.setAttribute("_JavaScript",
"alert('上传图片失败！请检查后重新尝试');window.history.back();");
return mapping.findForward("info");
} 调用的上传类中的部分代码：            Context ic = new InitialContext();
            ic = (Context) ic.lookup("java:comp/env/");
            szPath = (String) ic.lookup(filePath);            fileName = file.getFileName();
            if (fileName != null && !fileName.equals(""))
            {
                fullPath = prefix + szPath + SEPERATOR + fileSaveName;                File newFile = new File(fullPath);
                if (!newFile.exists())
                {
                    newFile.createNewFile();
                }                bis = new BufferedInputStream(file.getInputStream());
                bos = new BufferedOutputStream(new FileOutputStream(newFile));
                byte[] buffer = new byte[1024];
                int bytesRead = 0;
                long hastransfered = 0;
                long size = 10000*1024;                 //10000单位是Kb
                while ((bytesRead = bis.read(buffer, 0, 1024)) != -1)
                {
                    bos.write(buffer, 0, bytesRead);
                    hastransfered+=bytesRead;
                    if(hastransfered>=size)
                    {
                     return false;
                    }
                }                bis.close();
                bos.close();
                file.destroy();