private static String pathAndQueryString(HttpRequestMessage request) {
        // parsing the params cleans up any empty/null params using the logic of the HttpQueryParams class
        HttpQueryParams cleanParams =
                HttpQueryParams.parse(request.getQueryParams().toEncodedString());
        String cleanQueryStr = cleanParams.toEncodedString();
        if (cleanQueryStr == null || cleanQueryStr.isEmpty()) {
            return request.getPath();
        } else {
            return request.getPath() + "?" + cleanParams.toEncodedString();
        }
    }
Override to add custom modifications to the request before it goes out

@param headers
zuul-core/src/main/java/com/netflix/zuul/netty/server/OriginResponseReceiver.java