最近在研发一款O2O产品，考虑到分布式架构的需要，以前那一套.NET的Session管理方式已经不合用了。遂研究了一下Redis，发现基于这种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:
<!--Redis数据库编号（范围：0~15）--><add key="SessionRedisDBIndex" value="0"/><!--主Redis连接串--><add key="SessionRedisMaster" value="pass:192.168.1.236:6379"/><!--Session有效时长，单位：分钟--><add key="SessionTimeOut" value="120"/>Session基类：
public abstract class BaseSession { DateTime mExpiresTime = DateTime.Now; [JsonConverter(typeof(TimestampConverter))] public DateTime ExpiresTime { get { return mExpiresTime; } } /// <summary> /// 设置Session过期时间 /// </summary> /// <param name="aExpiresTime"></param> internal void SetExpiresTime(DateTime aExpiresTime) { mExpiresTime = aExpiresTime; } [JsonIgnore] /// <summary> /// 获取服务端ID /// </summary> public abstract string ServerID { get; } } public static class SessionService { /// <summary> /// Session有效时长,默认120分钟 /// </summary> static int TimeOutMinutes=120; /// <summary> /// Redis缓存访问对象 /// </summary> static ConnectionMultiplexer mRedisSession; /// <summary> /// Session管理 /// </summary> 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; } } /// <summary> /// 添加Session /// </summary> /// <typeparam name="T">Session对象类型</typeparam> /// <param name="aSession">要存为Session的对象</param> /// <param name="aPrefix">前缀</param> /// <returns>令牌</returns> public static string Add<T>(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<T>):" + ex.Message, "", "SessionError", "SessionError"); } return null; } /// <summary> /// 获取Session /// </summary> /// <typeparam name="T">Session对象类型</typeparam> /// <param name="aToken">令牌</param> /// <returns>令牌对应的Session对象</returns> public static T Get<T>(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<T>(fSessionValue); CheckExpireTime<T>(aToken, fEntity, client); } return fEntity; } catch (Exception ex) { Lib.LocalLog.Append("Session Error(Get<T>):" + ex.Message, "", "SessionError", "SessionError"); } return default(T); } /// <summary> /// 获取Session 字符串值 /// </summary> /// <param name="aToken">令牌</param> /// <returns>令牌对应的Session 字符串值</returns> public static string GetValue<T>(string aToken) where T : BaseSession { try { IDatabase client = mRedisSession.GetDatabase(); string fSessionValue = client.StringGet(aToken); if (fSessionValue != null) { CheckExpireTime<T>(aToken, JsonConvert.DeserializeObject<T>(fSessionValue), client); } return fSessionValue; } catch (Exception ex) { Lib.LocalLog.Append("Session Error(GetValue<T>):" + ex.Message, "", "SessionError", "SessionError"); } return null; } /// <summary> /// 删除Session /// </summary> /// <param name="aToken">令牌</param> public static void Remove<T>(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<T>(fSessionValue); client.KeyDelete(fEntity.ServerID); client.KeyDelete(aToken); } } catch (Exception ex) { Lib.LocalLog.Append("Session Error(Remove):" + ex.Message, "", "SessionError", "SessionError"); } } /// <summary> /// 令牌有效时间检查 /// </summary> /// <typeparam name="T"></typeparam> /// <param name="aToken">令牌</param> /// <param name="aSession"></param> static void CheckExpireTime<T>(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"); } } } }
