public static String getParam(MultiValueMap<String, String> parameters, String paramName) {
        String paramValue = parameters.getFirst(paramName);
        if (!StringUtils.hasText(paramValue) || parameters.get(paramName).size() != 1) {
            OAuthEndpointUtils.throwError(
                    OAuth2ErrorCodes.INVALID_REQUEST,
                    paramName,
                    OAuthEndpointUtils.ACCESS_TOKEN_REQUEST_ERROR_URI);
        }
        return paramValue;
    }
@author: zlt
@date: 2023/11/14
<p>
Blog: https://zlt2000.gitee.io
Github: https://github.com/zlt2000
zlt-uaa/src/main/java/com/central/oauth/utils/OAuthEndpointUtils.java