Java對字符串進行sha1加密

/**
     * 進行sha1加密
     * @param str
     * @return
     * @throws NoSuchAlgorithmException
     * @throws UnsupportedEncodingException
     */
    public String getSha1(@RequestParam String str) throws NoSuchAlgorithmException, UnsupportedEncodingException {
        if (null == str || str.length() == 0){
            return null;
        }
        char[] hexDigits = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
                'a', 'b', 'c', 'd', 'e', 'f'};
        try {
            MessageDigest mdTemp = MessageDigest.getInstance("SHA1");
            mdTemp.update(str.getBytes("UTF-8"));

            byte[] md = mdTemp.digest();
            int j = md.length;
            char[] buf = new char[j * 2];
            int k = 0;
            for (int i = 0; i < j; i++) {
                byte byte0 = md[i];
                buf[k++] = hexDigits[byte0 >>> 4 & 0xf];
                buf[k++] = hexDigits[byte0 & 0xf];
            }
            return new String(buf);
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }