/**
     * 对密码进行加密,并转换为十六进制
     * @param password
     * @return
     */
    private static String digest(String password){
        try {
            //获取一个加密对象 Java自带API
            MessageDigest md = MessageDigest.getInstance("sha1");//sha1为加密算法
            //加密
            byte[] digest = md.digest(password.getBytes());
            char[] chars = {'0','1','2','3','4','5','6','7','8','9','a','b','c','d','e'};
            StringBuilder sb = new StringBuilder();
            //处理加密结果
            for (byte b: digest) {
                //byte为一个字节8位,高四位右移4位与15求与
                sb.append(chars[(b>>4)&15]);
                //低四位直接与15求与
                sb.append(chars[b&15]);
            }
            return sb.toString();
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        }
     return null;   
    }