public class SmsEntity{
  private Integer id;
  private String mobile;
  private String ip;
  private Integer type;
  private Date time;
  private String captcha;

  // 省略构造方法和getter、setter方法
}

public interface SmsFilter {

  /**
   * 初始化该过滤器
   */
  void init() throws Exception;

  /**
   * 判断短信是否可以发送.
   * @param smsEntity 将要发送的短信内容
   * @return 可以发送则返回true, 否则返回false
   */
  boolean filter(SmsEntity smsEntity);

  /**
   * 销毁该过滤器
   */
  void destroy();

}

public class FrequencyFilter implements SmsFilter {
  /**
   * 发送间隔, 单位: 毫秒
   */
  private long sendInterval;
  private ConcurrentMap<String, Long> sendAddressMap = new ConcurrentHashMap<>();

  // 省略了部分无用代码

  @Override
  public boolean filter(SmsEntity smsEntity) {
    if(setSendTime(smsEntity.getMobile()) && setSendTime(smsEntity.getIp())){
      return true;
    }
    return false;
  }

  /**
   * 将发送时间修改为当前时间.
   * 如果距离上次发送的时间间隔大于{@link #sendInterval}则设置发送时间为当前时间. 否则不修改任何内容.
   *
   * @param id 发送手机号 或 ip
   * @return 如果成功将发送时间修改为当前时间, 则返回true. 否则返回false
   */
  private boolean setSendTime(String id) {
    long currentTime = System.currentTimeMillis();

    Long sendTime = sendAddressMap.putIfAbsent(id, currentTime);
    if(sendTime == null) {
      return true;
    }

    long nextCanSendTime = sendTime + sendInterval;
    if(currentTime < nextCanSendTime) {
      return false;
    }

    return sendAddressMap.replace(id, sendTime, currentTime);
  }
}

/**
 * 在上面代码的基础上, 再添加如下代码
 */
public class FrequencyFilter implements SmsFilter {
  private long cleanMapInterval;
  private Timer timer = new Timer("sms_frequency_filter_clear_data_thread");

  @Override
  public void init() {
    timer.schedule(new TimerTask() {
      @Override
      public void run() {
        cleanSendAddressMap();
      }
    }, cleanMapInterval, cleanMapInterval);
  }

  /**
   * 将sendAddressMap中的所有过期数据删除
   */
  private void cleanSendAddressMap() {
    long currentTime = System.currentTimeMillis();
    long expireSendTime = currentTime - sendInterval;

    for(String key : sendAddressMap.keySet()) {
      Long sendTime = sendAddressMap.get(key);
      if(sendTime < expireSendTime) {
        sendAddressMap.remove(key, sendTime);
      }
    }
  }

  @Override
  public void destroy() {
    timer.cancel();
  }
}

private boolean setSendTime(String id) {
  // 省略前面的代码
  if(sendAddressMap.replace(id, sendTime, currentTime)) {
    return true;
  }
  return sendAddressMap.putIfAbsent(id, currentTime) == null;
}

public class SmsService{
  private Sms sms;
  private List<SmsFilter> filters;
  private Properties template;

  // 省略了部分代码

  /**
   * 发送验证码
   *
   * @param smsEntity 发送短信的基本数据
   * @return 如果提交成功, 返回0. 否则返回其他值.
   */
  public int sendCaptcha(SmsEntity smsEntity){
    for(SmsFilter filter : filters) {
      if(!filter.filter(smsEntity)){
        return 1;
      }
    }
    if(SmsEntity.REGISTER_TYPE.equals(smsEntity.getType())) {
      sendRegisterSms(smsEntity);
    }
    else{
      return 2;
    }
    return 0;
  }

  /**
   * 发送注册验证码
   *
   * @param smsEntity 发送短信的基本数据
   */
  private void sendRegisterSms(SmsEntity smsEntity) {
    sms.sendMessage(smsEntity.getMobile(),
        template.getProperty("register").replace("{captcha}", smsEntity.getCaptcha()));
  }

}