apollo-adminservice/src/main/java/com/ctrip/framework/apollo/adminservice/filter/AdminServiceAuthenticationFilter.java/AdminServiceAuthenticationFilter/checkAccessToken
class AdminServiceAuthenticationFilter:  private boolean checkAccessToken(String token) {
    String accessTokens = bizConfig.getAdminServiceAccessTokens();

    // if user forget to configure access tokens, then default to pass
    if (Strings.isNullOrEmpty(accessTokens)) {
      return true;
    }

    // no need to check
    if (Strings.isNullOrEmpty(token)) {
      return false;
    }

    // update cache
    if (!accessTokens.equals(lastAccessTokens)) {
      synchronized (this) {
        accessTokenList = ACCESS_TOKEN_SPLITTER.splitToList(accessTokens);
        lastAccessTokens = accessTokens;
      }
    }

    return accessTokenList.contains(token);
  }