Redis中的StackExchange.redis在C#中的应用

Redis，基于这种Key-Value的内存数据库很适合来做分布式Session。本示例将基于StackExchange.Redis.dll进行实现，序列化使用的是Newtonsoft.json.dll。

为了避免APP等客户端重复登录导致同一个用户出现重复的Session，将以ServerID（可以是数据库主键）为服务端令牌，并生成一个新的GUID作为其客户端令牌，客户端令牌将返回给客户端。
两个令牌都将存储在Redis中，形成2个键值对，在服务端令牌中保存了其对应的客户端令牌ID。当同一用户再次登录时，将首先检查是否有基于其ServerID的服务端令牌存在，如果存在，则直接取其值（客户端令牌）返回给客户端，以此避免重复的Session浪费。

Web.config:

 "SessionRedisDBIndex" value="0"/>

 "SessionRedisMaster" value="pass:192.168.1.236:6379"/>

 "SessionTimeOut" value="120"/>

Session基类：

 public abstract class BaseSession
     {
         DateTime mExpiresTime = DateTime.Now;

         [JsonConverter(typeof(TimestampConverter))]
         public DateTime ExpiresTime
         {
             get { return mExpiresTime; }
         }

         ///
         /// 设置Session过期时间
         ///
         ///
         internal void SetExpiresTime(DateTime aExpiresTime)
         {
             mExpiresTime = aExpiresTime;
         }

         [JsonIgnore]
         ///
         /// 获取服务端ID
         ///
         public abstract string ServerID { get; }
     }

 public static class SessionService
    {
        ///
        /// Session有效时长,默认120分钟
        ///
        static int TimeOutMinutes=120;

        ///
        /// Redis缓存访问对象
        ///
        static ConnectionMultiplexer mRedisSession;

        ///
        /// Session管理
        ///
        static SessionService()
        {
            try
            {
                TimeOutMinutes = int.Parse(ConfigurationManager.AppSettings["SessionTimeOut"]);
                string[] redisMaster = ConfigurationManager.AppSettings["SessionRedisMaster"].Split(':');
                ConfigurationOptions fRedisConfig = new ConfigurationOptions()
                {
                    Password = redisMaster[0],
                    EndPoints ={ { redisMaster[1], int.Parse(redisMaster[2]) } },
                    KeepAlive = 180,
                    DefaultDatabase = int.Parse(ConfigurationManager.AppSettings["SessionRedisDBIndex"])
                };
                mRedisSession = ConnectionMultiplexer.Connect(fRedisConfig);
            }
            catch (Exception ex)
            {
                Lib.LocalLog.Append("Session Error(SessionService):" + ex.Message, "", "SessionError", "SessionError");
                throw ex;
            }
        }

        ///
        /// 添加Session
        ///
        /// Session对象类型
        /// 要存为Session的对象
        /// 前缀
        /// 令牌
        public static string Add(T aSession,string aPrefix="") where T:BaseSession
        {
            try
            {
                IDatabase client = mRedisSession.GetDatabase();
                aSession.SetExpiresTime(DateTime.Now.AddMinutes(TimeOutMinutes));
                string fExistToken = client.StringGet(aSession.ServerID);//获取服务端唯一码当前对应的客户端令牌
                if (fExistToken != null)
                {//存在客户端令牌
                    //更新客户端令牌
                    if (client.StringSet(fExistToken,
                        JsonConvert.SerializeObject(aSession),
                        aSession.ExpiresTime.Subtract(DateTime.Now)))
                    {
                        return fExistToken;
                    }
                }
                else
                {
                    string token = aPrefix + Guid.NewGuid().ToString("N");
                    if(client.StringSet(token,
                        JsonConvert.SerializeObject(aSession),
                        aSession.ExpiresTime.Subtract(DateTime.Now)) &&//添加Session
                       client.StringSet(aSession.ServerID,
                        token,
                        aSession.ExpiresTime.AddSeconds(-5).Subtract(DateTime.Now)))//绑定服务端唯一码与客户端令牌（将比Session早5秒失效）
                    {
                        return token;
                    }
                }
            }
            catch (Exception ex)
            {
                Lib.LocalLog.Append("Session Error(Add):" + ex.Message, "", "SessionError", "SessionError");
            }
            return null;
        }

        ///
        /// 获取Session
        ///
        /// Session对象类型
        /// 令牌
        /// 令牌对应的Session对象
        public static T Get(string aToken) where T : BaseSession
        {
            try
            {
                IDatabase client = mRedisSession.GetDatabase();
                T fEntity = null;
                string fSessionValue = client.StringGet(aToken);
                if (!string.IsNullOrEmpty(fSessionValue))
                {
                    fEntity = JsonConvert.DeserializeObject(fSessionValue);
                    CheckExpireTime(aToken, fEntity, client);
                }
                return fEntity;
            }
            catch (Exception ex)
            {
                Lib.LocalLog.Append("Session Error(Get):" + ex.Message, "", "SessionError", "SessionError");
            }
            return default(T);
        }

        ///
        /// 获取Session 字符串值
        ///
        /// 令牌
        /// 令牌对应的Session 字符串值
        public static string GetValue(string aToken) where T : BaseSession
        {
            try
            {
                IDatabase client = mRedisSession.GetDatabase();
                string fSessionValue = client.StringGet(aToken);
                if (fSessionValue != null)
                {
                    CheckExpireTime(aToken, JsonConvert.DeserializeObject(fSessionValue), client);
                }
                return fSessionValue;
            }
            catch (Exception ex)
            {
                Lib.LocalLog.Append("Session Error(GetValue):" + ex.Message, "", "SessionError", "SessionError");
            }
            return null;
        }

        ///
        /// 删除Session
        ///
        /// 令牌
        public static void Remove(string aToken) where T : BaseSession
        {
            try
            {
                IDatabase client = mRedisSession.GetDatabase();
                T fEntity = null;
                string fSessionValue = client.StringGet(aToken);
                if (!string.IsNullOrEmpty(fSessionValue))
                {
                    fEntity = JsonConvert.DeserializeObject(fSessionValue);
                    client.KeyDelete(fEntity.ServerID);
                    client.KeyDelete(aToken);
                }
            }
            catch (Exception ex)
            {
                Lib.LocalLog.Append("Session Error(Remove):" + ex.Message, "", "SessionError", "SessionError");
            }
        }

        ///
        /// 令牌有效时间检查
        ///
        ///
        /// 令牌
        ///
        static void CheckExpireTime(string aToken, T aSession, IDatabase client) where T : BaseSession
        {
            if (aSession.ExpiresTime.Subtract(DateTime.Now).TotalMinutes < 10)
            {//离Session过期时间小于10分钟，延长Session有效期
                try
                {
                    aSession.SetExpiresTime(DateTime.Now.AddMinutes(TimeOutMinutes));
                    client.StringSet(aToken, JsonConvert.SerializeObject(aSession), aSession.ExpiresTime.Subtract(DateTime.Now));
                    client.KeyExpire(aSession.ServerID, aSession.ExpiresTime.AddSeconds(-5).Subtract(DateTime.Now));
                }
                catch (Exception ex)
                {
                    Lib.LocalLog.Append("Session Error(6):" + ex.Message, "", "SessionError", "SessionError");
                }
            }
        }
    }