JSP短信验证码功能如何实现短信发送失败重试机制？
<%
String phoneNumber = request.getParameter("phoneNumber");
String code = generateCode(); // 生成验证码
if (phoneNumber != null && !phoneNumber.isEmpty()) {
boolean sendSuccess = RetryUtil.sendSMSWithRetry(phoneNumber, code);
if (sendSuccess) {
out.println("短信发送成功！");
} else {
out.println("短信发送失败，请稍后再试！");
}
} else {
out.println("请输入手机号码！");
}
%>