public void storeAccessToken(OAuth2AccessToken token, OAuth2Authentication authentication) {
    String refreshToken = null;
    if (token.getRefreshToken() != null) {
      refreshToken = token.getRefreshToken().getValue();
    }

    // the JdbcTokenStore removes the existing token for this token_id [if it exists]
    // We'll avoid doing so for now, unless a compelling reason to do otherwise presents itself
    //        if (readAccessToken(token.getValue()) != null) {
    //            removeAccessToken(token.getValue());
    //        }

    Map<String, AttributeValueUpdate> updates = new HashMap<String, AttributeValueUpdate>();
    updates.put(
        schema.getAccessColumnToken(),
        new AttributeValueUpdate(
            new AttributeValue().withB(serializeAccessToken(token)), AttributeAction.PUT));
    DynamoDBUtils.nullSafeUpdateS(
        updates,
        schema.getAccessColumnAuthenticationId(),
        authenticationKeyGenerator.extractKey(authentication));
    if (authentication.isClientOnly()
        || authentication.getName() == null
        || authentication.getName().length() == 0) {
      DynamoDBUtils.nullSafeUpdateS(
          updates, schema.getAccessColumnUserName(), schema.getAccessNullUserToken());
      updates.put(
          schema.getAccessColumnIsNullUser(),
          new AttributeValueUpdate(
              new AttributeValue().withN(schema.getAccessIsNullUserTrueToken()),
              AttributeAction.PUT));
    } else {
      DynamoDBUtils.nullSafeUpdateS(
          updates, schema.getAccessColumnUserName(), authentication.getName());
      DynamoDBUtils.nullSafeUpdateS(updates, schema.getAccessColumnIsNullUser(), null);
    }

    DynamoDBUtils.nullSafeUpdateS(
        updates, schema.getAccessColumnClientId(), authentication.getOAuth2Request().getClientId());
    updates.put(
        schema.getAccessColumnAuthentication(),
        new AttributeValueUpdate(
            new AttributeValue().withB(serializeAuthentication(authentication)),
            AttributeAction.PUT));
    DynamoDBUtils.nullSafeUpdateS(
        updates, schema.getAccessColumnRefreshToken(), extractTokenKey(refreshToken));

    dynamoDBTemplate.update(
        schema.getAccessTableName(), //
        Collections.singletonMap(
            schema.getAccessColumnTokenId(),
            new AttributeValue(extractTokenKey(token.getValue()))), //
        updates);
  }
  public void storeRefreshToken(
      OAuth2RefreshToken refreshToken, OAuth2Authentication authentication) {
    Map<String, AttributeValueUpdate> updates = new HashMap<String, AttributeValueUpdate>();
    updates.put(
        schema.getRefreshColumnToken(),
        new AttributeValueUpdate(
            new AttributeValue().withB(serializeRefreshToken(refreshToken)), AttributeAction.PUT));
    updates.put(
        schema.getRefreshColumnAuthentication(),
        new AttributeValueUpdate(
            new AttributeValue().withB(serializeAuthentication(authentication)),
            AttributeAction.PUT));

    dynamoDBTemplate.update(
        schema.getRefreshTableName(), //
        Collections.singletonMap(
            schema.getRefreshColumnTokenId(),
            new AttributeValue(extractTokenKey(refreshToken.getValue()))), //
        updates);
  }