架构师训练营第十一周作业

   /**
     * <p>系统使用SHA-256加密用户密码</p>
     *
     * @param str 需要加密的字符串
     * @return
     */
    private static String getSHA256(String str) {
        if (str == null || str.equals(""))
            return null;
        String encodeStr = "";
        try {
            MessageDigest messageDigest = MessageDigest.getInstance("SHA-256");
            messageDigest.update(str.getBytes());
            encodeStr =  byte2Hex(messageDigest.digest());
        }catch (NoSuchAlgorithmException exception){
            // 异常处理
        }
        return encodeStr;
    }
    private static String byte2Hex(byte[] bytes) {
        StringBuffer stringBuffer = new StringBuffer();
        for (byte aByte : bytes) {
            if(aByte < 16)
                stringBuffer.append("0");
            stringBuffer.append(Integer.toHexString(aByte & 0xFF));
        }
        return stringBuffer.toString();
    }
    /**
     *
     *
     * @param userID 用户ID
     * @param plainTextPW 用户密码明文
     * @param ciphertextPW 用户密码密文
     * @return
     */
    public static boolean checkPW(String userID, String plainTextPW, String cipherTextPW) {
        //使用userID + plainTextPW构建字符串做SHA-256单向散列
        String encodePlainTextPW = getSHA256(userID + plainTextPW);
        return cipherTextPW.equals(encodePlainTextPW);
    }