private static <T> String fromBean(T obj) throws Exception {
        String json = "{}";
        log.debug(String.format("method start Object[obj:%s]", obj));
        if (obj != null) {   
            Class<?> cls = obj.getClass();
            Field[] fields = Reflect.getFields(cls);
            StringBuilder sb = new StringBuilder(fields.length * 10); //假设10是一个键值对的平均长度
            sb.append("{");
            Object value;
            for (Field field : fields) {
                value = Reflect.getFieldValue(obj, field);
                sb.append("\"").append(field.getName()).append("\":")
                    .append(fromObject(value)).append(",");
            }
            sb.setCharAt(sb.length() - 1, '}');
            json = sb.toString();
        }
        log.debug(String.format("method stop return:String[%s]", json));
        return json;
    }