private static String fromCollection(Collection<?> collection) throws Exception {
        String json = "[]";
        log.debug(String.format("method start Collection[collection:%s]", collection));
        if (collection != null && collection.size() > 0) {
            StringBuilder sb = new StringBuilder(collection.size() * 10); //假设一个元素平均长度为10
            sb.append("[");
            for (Object obj : collection) {
                sb.append(fromObject(obj)).append(",");
            }
            sb.setCharAt(sb.length() - 1, ']');
            json = sb.toString();
        } 
        log.debug(String.format("method stop return:String[%s]", json));
        return json;
    }