{
  ‘typ‘: ‘JWT‘,
  ‘alg‘: ‘HS256‘
}

    /// <summary>
    /// token管理类
    /// </summary>
    public class TokenManager
    {
        //私有字段建议放到配置文件中
        /// <summary>
        /// 秘钥  4的倍数  长度大于等于24
        /// </summary>
        private static string _secret = "levy0102030405060708asdf";
        /// <summary>
        /// 发布者
        /// </summary>
        private static string _issuer = "levy";

        /// <summary>
        /// 生成token
        /// </summary>
        /// <param name="tokenStr">需要签名的数据  </param>
        /// <param name="expireHour">默认3天过期</param>
        /// <returns>返回token字符串</returns>
        public static string GenerateToken(string tokenStr, int expireHour = 3 * 24) //3天过期
        {
            var key1 = new SymmetricSecurityKey(Convert.FromBase64String(_secret));
            var cred = new SigningCredentials(key1, SecurityAlgorithms.HmacSha256);
            var claims = new[]
            {
                new Claim("sid",tokenStr),
                //new Claim(ClaimTypes.Name,name), //示例  可使用ClaimTypes中的类型
            };
            var token = new JwtSecurityToken(
                issuer: _issuer,//签发者
                notBefore: DateTime.Now,//token不能早于这个时间使用
                expires: DateTime.Now.AddHours(expireHour),//添加过期时间
                claims: claims,//签名数据
                signingCredentials: cred//签名
                );
            //解决一个不知什么问题的PII什么异常
            IdentityModelEventSource.ShowPII = true;
            return new JwtSecurityTokenHandler().WriteToken(token);
        }

        /// <summary>
        /// 得到Token中的验证消息
        /// </summary>
        /// <param name="token"></param>
        /// <param name="dateTime"></param>
        /// <returns></returns>
        public static string ValidateToken(string token, out DateTime dateTime)
        {
            dateTime = DateTime.Now;
            var principal = GetPrincipal(token, out dateTime);

            if (principal == null)
                return default(string);

            ClaimsIdentity identity = null;
            try
            {
                identity = (ClaimsIdentity)principal.Identity;
            }
            catch (NullReferenceException)
            {
                return null;
            }
            //identity.FindFirst(ClaimTypes.Name).Value;
            return identity.FindFirst("sid").Value;
        }

        /// <summary>
        /// 从Token中得到ClaimsPrincipal对象
        /// </summary>
        /// <param name="token"></param>
        /// <returns></returns>
        private static ClaimsPrincipal GetPrincipal(string token, out DateTime dateTime)
        {
            try
            {
                dateTime = DateTime.Now;
                var tokenHandler = new JwtSecurityTokenHandler();
                var jwtToken = (JwtSecurityToken)tokenHandler.ReadToken(token);

                if (jwtToken == null)
                    return null;

                var key = Convert.FromBase64String(_secret);

                var parameters = new TokenValidationParameters()
                {
                    RequireExpirationTime = true,
                    ValidateIssuer = true,//验证创建该令牌的发布者
                    ValidateLifetime = true,//检查令牌是否未过期，以及发行者的签名密钥是否有效
                    ValidateAudience = false,//确保令牌的接收者有权接收它
                    IssuerSigningKey = new SymmetricSecurityKey(key),
                    ValidIssuer = _issuer//验证创建该令牌的发布者
                };
                //验证token 
                var principal = tokenHandler.ValidateToken(token, parameters, out var securityToken);
                //若开始时间大于当前时间 或结束时间小于当前时间 则返回空
                if (securityToken.ValidFrom.ToLocalTime() > DateTime.Now || securityToken.ValidTo.ToLocalTime() < DateTime.Now)
                {
                    dateTime = DateTime.Now;
                    return null;
                }
                dateTime = securityToken.ValidTo.ToLocalTime();//返回Token结束时间
                return principal;
            }
            catch (Exception e)
            {
                dateTime = DateTime.Now;
                LogHelper.Logger.Fatal(e, "Token验证失败");
                return null;
            }
        }
    }

        [HttpGet]
        [Route("testtoken")]
        public ActionResult TestToken()
        {
            var token = TokenManager.GenerateToken("测试token的生成");
            Response.Headers["token"] = token;
            Response.Headers["Access-Control-Expose-Headers"] = "token";//一定要添加这一句  不然前端是取不到token字段的值的！更别提存store了。
            return Succeed(token);
        }

        [HttpPost]
        [Route("validtoken")]
        public ActionResult ValidToken([FromHeader]string token)
        {
            var str = TokenManager.ValidateToken(token, out DateTime date);
            if (!string.IsNullOrEmpty(str) || date > DateTime.Now)
            {
                //当token过期时间小于五小时，更新token并重新返回新的token
                if (date.AddHours(-5) > DateTime.Now) return Succeed($"Token字符串:{str},过期时间：{date}");
                var nToken = TokenManager.GenerateToken(str);
                Response.Headers["token"] = nToken;
                token = nToken;
                Response.Headers["Access-Control-Expose-Headers"] = "token";
            }
            else
            {
                return Fail(101, "未取得授权信息");
            }
            return Succeed($"Token字符串:{str},过期时间：{DateTime.Now.AddHours(3 * 24)}");
        }