实现分布式的Membership和上下文传递

1、实现分布式的Membership和上下文传递通过上一篇了解了模块内基本的层次划分之后，接下来我们来聊聊PetShop中一些基本基础功能的实现，以及一些设计、架构上的应用如何同WCF进行集成。本篇讨论两个问题：实现分布式的Membership和客户端到服务端上下文（Context）的传递。一、 如何实现用户验证对登录用户的验证是大部分应用所必需的，对于ASP.NET来说，用户验证及帐号管理实现在成员资格（Membership）模块中。同ASP.NET的其他模块一样，微软在设计Membership的时候，为了实现更好地可扩展性，采用了策略（Strategy）设计模式：将模块相关的功能定义在被称为P

2、rovider的抽象类型中，并通过继承它提供具体的Provider。如果这些原生的Provider不能满足你的需求，你也可以通过继承该抽象的Provider，创建自定义的Provider。通过ASP.NET提供的配置，你可以很轻易地把自定义的Provider应用到你的应用之中。在一般情况下，最终的编程人员并不通过Provider调用相关的功能，而是通过一个外观（Facade）类实现对相关功能的调用。ASP.NET成员资格模块的设计基本上可以通过下面的类图1反映出来：最终的编程人员通过外观类型（Faade Class）Membership调用成员资格相关的功能，比如用户认证、用户注册、修改密码等

3、；Membership通过抽象类MembershipProvider提供所有的功能，至于最终的实现，则定义在一个个具体的MembershipProvider中。基于成员资格信息不同的存储方式，ASP.NET提供了两个原生的MembershipProvider：SqlMembershipProvider和ActiveDirectoryMembershipProvider，前者基于SQL Server数据库，后者基于AD。如果这两个MembershipProvider均不能满足需求，我们还可以自定义MembershipProvider。clip_image002图1 ASP.NET Members

4、hip 设计原理我们的案例并不会部署于AD之中，所以不能使用ActiveDirectoryMembershipProvider；直接通过Web服务器进行数据库的存取又不符合上述物理部署的要求（通过应用服务器进行数据库访问），所以SqlMembershipProvider也不能为我们所用。为此需要自定义MembershipProvider，通过WCF服务调用的形式提供成员资格所有功能的实现。我们将该自定义MembershipProvider称为RemoteMembershipProvider。图2揭示了RemoteMembershipProvider实现的原理：RemoteMembershipP

5、rovider通过调用WCF服务MembershipService提供对成员资格所有功能的实现；MembershipService则通过调用Membership实现服务；最终的实现还是落在了SqlMembershipProvider这个原生的MembershipProvider上。clip_image004图2 RemoteMembershipProvider实现原理1、服务契约和服务实现首先来看看MembershipService实现的服务契约的定义。由于MembershipService最终是为RemoteMembershipProvider这个自定义MembershipProvider服

6、务的，所以服务操作的定义是基于MembershipProvider的API定义。MembershipProvider包含两种类型的成员：属性和方法，简单起见，我们可以为MembershipProvider每一个抽象方法定义一个匹配的服务操作；而对于所有属性，完全采用服务端（应用服务器）的MembershipProvider相关属性。在RemoteMembershipProvider初始化的时候通过调用MembershipService获取所有服务端MembershipProvider的配置信息。为此，我们为MembershipProvider的所有属性定义了一个数据契约：MembershipC

7、onfigData。在PetShop中，MembershipConfigData和服务契约一起定义在Infrastructures.Service.Interface项目中。 1: using System.Runtime.Serialization; 2: using System.Web.Security; 3: namespace Artech.PetShop.Infrastructures.Service.Interface 4: 5: DataContract(Namespace = 6: public class MembershipConfigData 7: 8: DataMem

8、ber 9: public string ApplicationName 10: get; set; 11: 12: DataMember 13: public bool EnablePasswordReset 14: get; set; 15: 16: DataMember 17: public bool EnablePasswordRetrieval 18: get; set; 19: 20: DataMember 21: public int MaxInvalidPasswordAttempts 22: get; set; 23: 24: DataMember 25: public in

9、t MinRequiredNonAlphanumericCharacters 26: get; set; 27: 28: DataMember 29: public int MinRequiredPasswordLength 30: get; set; 31: 32: DataMember 33: public int PasswordAttemptWindow 34: get; set; 35: 36: DataMember 37: public MembershipPasswordFormat PasswordFormat 38: get; set; 39: 40: DataMember

10、41: public string PasswordStrengthRegularExpression 42: get; set; 43: 44: DataMember 45: public bool RequiresQuestionAndAnswer 46: get; set; 47: 48: DataMember 49: public bool RequiresUniqueEmail 50: get; set; 51: 52: 在服务契约中，定义了一个额外的方法GetMembershipConfigData获取服务端MembershipProvider的所有配置信息，而对于服务操作的定义，

11、则与MembershipProvider同名抽象方法相对应。 1: using System.ServiceModel; 2: using System.Web.Security; 3: namespace Artech.PetShop.Infrastructures.Service.Interface 4: 5: ServiceContract(Namespace= 6: public interface IMembershipService 7: 8: OperationContract 9: bool ChangePassword(string username, string oldP

12、assword, string newPassword); 10: OperationContract 11: bool ChangePasswordQuestionAndAnswer(string username, string password, string newPasswordQuestion, string newPasswordAnswer); 12: OperationContract 13: MembershipUser CreateUser(string username, string password, string email, string passwordQue

13、stion, string passwordAnswer, bool isApproved, object providerUserKey, out MembershipCreateStatus status); 14: OperationContract 15: bool DeleteUser(string username, bool deleteAllRelatedData); 16: OperationContract 17: MembershipUserCollection FindUsersByEmail(string emailToMatch, int pageIndex, in

14、t pageSize, out int totalRecords); 18: OperationContract 19: MembershipUserCollection FindUsersByName(string usernameToMatch, int pageIndex, int pageSize, out int totalRecords); 20: OperationContract 21: MembershipUserCollection GetAllUsers(int pageIndex, int pageSize, out int totalRecords); 22: Ope

15、rationContract 23: int GetNumberOfUsersOnline(); 24: OperationContract 25: string GetPassword(string username, string answer); 26: OperationContract(Name=GetUserByName) 27: MembershipUser GetUser(string username, bool userIsOnline); 28: OperationContract(Name=GetUserByID) 29: MembershipUser GetUser(

16、object providerUserKey, bool userIsOnline); 30: OperationContract 31: string GetUserNameByEmail(string email); 32: OperationContract 33: string ResetPassword(string username, string answer); 34: OperationContract 35: bool UnlockUser(string userName); 36: OperationContract 37: void UpdateUser(Members

17、hipUser user); 38: OperationContract 39: bool ValidateUser(string username, string password); 40: OperationContract 41: MembershipConfigData GetMembershipConfigData(); 42: 43: 服务的实现，则异常简单，我们须要做的仅仅是通过Membership.Provider获得当前的MembershipProvider，调用同名的属性或方法即可。MembershipService定义在Infrastructures.Service中，

18、定义如下： 1: using System.Web.Security; 2: using Artech.PetShop.Infrastructures.Service.Interface; 3: namespace Artech.PetShop.Infrastructures.Service 4: 5: public class MembershipService : IMembershipService 6: 7: #region IMembershipService Members 8: 9: public bool ChangePassword(string username, stri

19、ng oldPassword, string newPassword) 10: 11: return Membership.Provider.ChangePassword(username, oldPassword, newPassword); 12: 13: 14: public bool ChangePasswordQuestionAndAnswer(string username, string password, string newPasswordQuestion, string newPasswordAnswer) 15: 16: return Membership.Provide

20、r.ChangePasswordQuestionAndAnswer(username, password, newPasswordQuestion, newPasswordAnswer); 17: 18: /其他成员 19: public MembershipConfigData GetMembershipConfigData() 20: 21: return new MembershipConfigData 22: 23: ApplicationName = Membership.Provider.ApplicationName, 24: EnablePasswordReset = Memb

21、ership.Provider.EnablePasswordReset, 25: EnablePasswordRetrieval = Membership.Provider.EnablePasswordRetrieval, 26: MaxInvalidPasswordAttempts = Membership.Provider.MaxInvalidPasswordAttempts, 27: MinRequiredNonAlphanumericCharacters = Membership.Provider.MinRequiredNonAlphanumericCharacters, 28: Mi

22、nRequiredPasswordLength = Membership.Provider.MinRequiredPasswordLength, 29: PasswordAttemptWindow = Membership.Provider.PasswordAttemptWindow, 30: PasswordFormat = Membership.Provider.PasswordFormat, 31: PasswordStrengthRegularExpression = Membership.Provider.PasswordStrengthRegularExpression, 32:

23、RequiresQuestionAndAnswer = Membership.Provider.RequiresQuestionAndAnswer, 33: RequiresUniqueEmail = Membership.Provider.RequiresUniqueEmail 34: ; 35: 36: 37: #endregion 38: 39: 2、RemoteMembershipProvider的实现由于RemoteMembershipProvider完全通过调用WCF服务的方式提供对所有成员资格功能的实现，所以进行RemoteMembershipProvider配置时，配置相应的终

24、结点就可以了。 1: 2: 3: 4: 5: 6: 7: 8: 9: 10: 11: 12: 13: 14: 15: 在RemoteMembershipProvider中，通过Initialize方法获取配置的终结点名称并创建服务代理。通过该代理调用GetMembershipConfigData操作获取服务端MembershipProvider的配置信息，并对RemoteMembershipProvider进行初始化，RemoteMembershipProvider定义如下： 1: using System.Collections.Specialized; 2: using System.Co

25、nfiguration; 3: using System.Linq; 4: using System.Web.Security; 5: using Artech.PetShop.Common; 6: using Artech.PetShop.Infrastructures.Service.Interface; 7: 8: namespace Artech.PetShop.Infrastructures 9: 10: public class RemoteMembershipProvider : MembershipProvider 11: 12: private bool _enablePas

26、swordReset; 13: private bool _enablePasswordRetrieval; 14: /其他字段成员 15: 16: public IMembershipService MembershipProxy 17: get; private set; 18: 19: public override int MaxInvalidPasswordAttempts 20: 21: get return this._maxInvalidPasswordAttempts; 22: 23: 24: /其他属性成员 25: public override void Initiali

27、ze(string name, NameValueCollection config) 26: 27: if (!config.AllKeys.Contains(endpoint) 28: 29: throw new ConfigurationErrorsException(Missing the mandatory endpoint configuraiton property.); 30: 31: 32: this.MembershipProxy = ServiceProxyFactory.Create(configendpoint); 33: base.Initialize(name,

28、config); 34: MembershipConfigData configData = this.MembershipProxy.GetMembershipConfigData(); 35: this.ApplicationName = configData.ApplicationName; 36: this._enablePasswordReset = configData.EnablePasswordReset; 37: this._enablePasswordRetrieval = configData.EnablePasswordRetrieval; 38: /. 39: 40:

29、 41: 对于其他抽象方法的实现，仅仅须要通过上面创建的服务代理，调用相应的服务操作即可。注： 为了避免在服务操作调用后频繁地进行服务代理的关闭（Close）和终止（Abort）操作，我们采用基于AOP的方式实现服务的调用，将这些操作封装到一个自定义的RealProxy中，并通过ServiceProxyFactory创建该RealProxy的TransparentProxy。相关实现可以参考WCF技术剖析（卷1）第九章。二、 上下文的共享及跨域传递在进行基于N-Tier的应用开发中，我们往往需要在多个层次之间共享一些上下文（Context）信息，比如当前用户的Profile信息；在进行远程服务

30、调用时，也经常需要进行上下文信息的跨域传递。比如在PetShop中，服务端进行审核（Audit）的时候，须要获取当前登录的用户名。而登录用户名仅仅对于Web服务器可得，所以在每次服务调用的过程中，需要从客户端向服务端传递。1、ApplicationContext基于上下文的共享，我创建了一个特殊的类型：ApplicationContext。ApplicationContext定义在Common项目中，简单起见，直接将其定义成字典的形式。至于上下文数据的真正存储，如果当前HttpContext存在，将其存储与HttpSessionState中，否则将其存储于CallContext中。注： 由于C

31、allConext将数据存储于当前线程的TLS（Thread Local Storage）中，实际上HttpContext最终也采用这样的存储方式，所以ApplicaitonContext并不提供上下文信息跨线程的传递。 1: using System.Collections.Generic; 2: using System.Runtime.Remoting.Messaging; 3: using System.Web; 4: namespace Artech.PetShop.Common 5: 6: public class ApplicationContext:Dictionary 7:

32、8: public const string ContextKey = Artech.PetShop.Infrastructures.ApplicationContext; 9: public const string ContextHeaderLocalName = ApplicationContext; 10: public const string ContextHeaderNamespace = 11: public static ApplicationContext Current 12: 13: get 14: 15: if (HttpContext.Current != null

33、) 16: 17: if (HttpContext.Current.SessionContextKey = null) 18: 19: HttpContext.Current.SessionContextKey = new ApplicationContext(); 20: 21: 22: return HttpContext.Current.SessionContextKey as ApplicationContext; 23: 24: 25: if (CallContext.GetData(ContextKey) = null) 26: 27: CallContext.SetData(Co

34、ntextKey, new ApplicationContext(); 28: 29: 30: return CallContext.GetData(ContextKey) as ApplicationContext; 31: 32: set 33: 34: if (HttpContext.Current != null) 35: 36: HttpContext.Current.SessionContextKey = value; ; 37: 38: else 39: 40: CallContext.SetData(ContextKey, value); 41: 42: 43: 44: pub

35、lic string UserName 45: 46: get 47: 48: if (!this.ContainsKey(_UserName ) 49: 50: return string.Empty; 51: 52: 53: return (string)this_UserName; 54: 55: set 56: 57: this_UserName = value; 58: 59: 60: 61: 2、ApplicationContext在WCF服务调用中的传递下面我们来介绍一下如何实现上下文信息在WCF服务调用过程中的“隐式”传递。在PetShop中，我们通过WCF的扩展实现此项功能。

36、上下文传递的实现原理很简单：在客户端，将序列化后的当前上下文信息置于出栈（Outgoing）消息的SOAP报头中，并为报头指定一个名称和命名空间；在服务端，在服务操作执行之前，通过报头名称和命名空间将上下文SOAP报头从入栈（Incoming）消息中提取出来，进行反序列化，并将其设置成服务端当前的上下文。所以，上下文的传递实际上包含两个方面：SOAP报头的添加和提取。我们通过两个特殊的WCF对象来分别实现这两个功能：ClientMessageInspector和CallContextInitializer，前者在客户端将上下文信息封装成SOAP报头，并将其添加到出栈消息报头集合；后者则在服务端

37、实现对上下文SOAP报头的提取和当前上下文的设置。关于ClientMessageInspector和CallContextInitializer，本书的下一卷关于客户端和服务端处理流程，以及WCF扩展的部分，还将进行详细的介绍。自定义的ClientMessageInspector和CallContextInitializer定义在Infrastructures项目中，下面是相关代码实现：ContextSendInspector： 1: using System.ServiceModel; 2: using System.ServiceModel.Channels; 3: using Syste

38、m.ServiceModel.Dispatcher; 4: using System.Threading; 5: using Artech.PetShop.Common; 6: namespace Artech.PetShop.Infrastructures 7: 8: public class ContextSendInspector: IClientMessageInspector 9: 10: public void AfterReceiveReply(ref Message reply, object correlationState) 11: 12: 13: public objec

39、t BeforeSendRequest(ref Message request, IClientChannel channel) 14: 15: if (string.IsNullOrEmpty(ApplicationContext.Current.UserName) 16: 17: ApplicationContext.Current.UserName = Thread.CurrentPrincipal.Identity.Name; 18: 19: request.Headers.Add(new MessageHeader( 20: ApplicationContext.Current).G

40、etUntypedHeader( 21: ApplicationContext.ContextHeaderLocalName, ApplicationContext.ContextHeaderNamespace); 22: 23: return null; 24: 25: 26: ContextReceivalCallContextInitializer： 1: using System.ServiceModel; 2: using System.ServiceModel.Channels; 3: using System.ServiceModel.Dispatcher; 4: using A

41、rtech.PetShop.Common; 5: namespace Artech.PetShop.Infrastructures 6: 7: public class ContextReceivalCallContextInitializer : ICallContextInitializer 8: 9: public void AfterInvoke(object correlationState) 10: 11: ApplicationContext.Current.Clear(); 12: 13: 14: public object BeforeInvoke(InstanceConte

42、xt instanceContext, IClientChannel channel, Message message) 15: 16: ApplicationContext.Current = message.Headers.GetHeader(ApplicationContext.ContextHeaderLocalName, ApplicationContext.ContextHeaderNamespace); 17: return null; 18: 19: 20: 和应用大部分自定义扩展对象一样，上面自定义的ClientMessageInspector和CallContextInit

43、ializer可以通过相应的WCF行为（服务行为、终结点行为、契约行为或者操作行为）应用到WCF执行管道中。在这里我定义了一个行为类型：ContextPropagationBehaviorAttribute，它同时实现了IServiceBehavior和 IEndpointBehavior，所以既是一个服务行为，也是一个终结点行为。同时ContextPropagationBehaviorAttribute还继承自Attribute，所以可以通过特定的方式应用该行为。自定义ClientMessageInspector和CallContextInitializer分别通过ApplyClientBe

44、havior和ApplyDispatchBehavior方法应用到WCF客户端运行时和服务端运行时。ContextPropagationBehaviorAttribute定义如下： 1: using System; 2: using System.ServiceModel.Description; 3: using System.ServiceModel.Dispatcher; 4: namespace Artech.PetShop.Infrastructures 5: 6: public class ContextPropagationBehaviorAttribute:Attribute, IServiceBehavior,IEndpointBehavior 7: 8: #region IServiceBehavior Members 9: publicvoidAddBindingParameters(ServiceDescription ser