将id属性定义为objectid可以生成12个字母数字字符的id

跟随这个亲爱的：

public static String getAlphaNumbericRandom(int length) {
         String chars = "abcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";

            int numberOfCodes = 0;//controls the length of alpha numberic string
            String code = "";
            while (numberOfCodes < length) {
                char c = chars.charAt((int) (Math.random() * chars.length()));
                code += c;
                numberOfCodes++;
            }
            return code;
        }

调用此方法并传递长度（例如4、5等）