專案中遇到一個問題，需要使用MD5加密後將字串上傳，嘗試了幾次發現總是返回簽名錯誤。網上查了很久以後發現
MD5加密後的byte[]陣列不能直接toString()
需要將byte[]每一位都轉成16進位制輸出，程式碼如下

    private static String byteToString(String bs) {
        StringBuilder stringBuilder = new StringBuilder();

        try {
            byte[] md5s = MessageDigest.getInstance("MD5"
 
).digest(bs.getBytes("utf-8"));
            for (byte b : md5s) {
                stringBuilder.append(String.format("%02x", new Integer(b & 0xff)));
            }
            return stringBuilder.toString();
        } catch (Exception e) {
            throw new FatalException("md5物件初始化失敗", e);
        }

    }