private static String getFileExtName(String filename) {
        if ((filename != null) && (filename.length() > 0)) {
            int dot = filename.lastIndexOf('.');
            if ((dot > -1) && (dot < (filename.length() - 1))) {
                return filename.substring(dot);
            }
        }
        return filename;
    }
Construct RequestDispatcher from web config

@param config  the web configure object
inlong-tubemq/tubemq-server/src/main/java/org/apache/inlong/tubemq/server/master/web/simplemvc/RequestDispatcher.java