WCF技术剖析之三十三：你是否了解WCF事务框架体系内部的工作机制？[上篇]

 1: [AttributeUsage(AttributeTargets.Method)]

 2: public sealed class TransactionFlowAttribute : Attribute, IOperationBehavior

 3: { 

 4: public TransactionFlowAttribute(TransactionFlowOption transactions);

 5: void IOperationBehavior.AddBindingParameters(OperationDescription description, BindingParameterCollection parameters)

 6: {

 7: //将TransactionFlow选项（NotAllwed、Allowed和Mandatory）存入绑定上下文

 8: AddTransactionFlowOptionInBindingContext();

 9: }

 10: void IOperationBehavior.ApplyClientBehavior(OperationDescription description, ClientOperation proxy){ }

 11: void IOperationBehavior.ApplyDispatchBehavior(OperationDescription description, DispatchOperation dispatch) { }

 12: void IOperationBehavior.Validate(OperationDescription description) { }

 13: 

 14: public TransactionFlowOption Transactions { get; }

 15: }

也就是通过AddBindingParameters这个方法，将设置的TransactionFlow选项传入了绑定上下文（Binding Context），使得通过绑定创建的信道（Channel）可以获取该选项，并根据相应的值控制自身消息处理的行为。在这里，真正使用到该TransactionFlow选项的信道，就是通过事务绑定的TransactionFlowBindingElement创建的事务信道。关于绑定、绑定元素和信道之间的关系，在《WCF技术剖析（卷1）》的第3章有详细的介绍。 二、 事务绑定：实现事务的流转

由于消息交换是WCF进行通信的唯一手段，所以事务的流转最终需要将事务本身作为消息的一部分进行传输。WCF采用不同的事务处理协议（OleTx和WS-AT），反映在消息交换上就是采用怎样的格式对事务进行格式化，以及将格式化的事务信息与消息（主要是SOAP）进行绑定。在WCF的整个事务处理体系结构中，事务的格式化和消息绑定的操作通过事务绑定实现。

我们所说的事务绑定就是包含有TransactionFlowBindingElement绑定元素，并且TransactionFlow开关被开启的绑定。对于客户端来说，TransactionFlowBindingElement创建事务信道工厂（TransactionChannelFactory），而基于不同的信道形状（Channel Shape）和对会话的支持，事务信道工厂会创建相应的事务信道，比如事务输出信道（TransactionOutputChannel）、事务请求信道（TransactionRequestChannel）和事务双工信道（TransactionDuplexChannel）等等。对于服务端来说，TransactionFlowBindingElement会创建事务信道监听器（TransactionChannelListener），与客户端类似，事务信道监听器也会创建基于不同信道形状（Channel Shape）和对会话的支持的事务信道，比如事务输入信道（TransactionInputChannel）、事务回复信道（TransactionReplyChannel）和事务双工信道（TransactionDuplexChannel）等。事务流转相关的绑定元素、绑定管理器（信道工厂和信道监听器）和信道之间的关系如图1所示。

图1 事务流转相关的绑定元素、信道管理器和信道结构

客户端的事务信道需要将当前事务写入消息，而服务端的事务信道则需要将流入的事务从服务中读出来。WCF将事务的读写操作定义在一个称为TransactionFormatter的类型中。不过，这是一个内部（Internal）类型不能直接使用。TransactionFormatter的定义大体上如下面的代码所示，其中ReadTransaction和WriteTransaction分别实现对事务的读取和写入操作。事务通过TransactionInfo对象的形式被读取出来，TransactionInfo是也是一个内部对象，我们可以通过调用UnmarshalTransaction得到真正的Transaction对象。

 3: //其他成员

 4: public abstract TransactionInfo ReadTransaction(Message message);

 5: public abstract void WriteTransaction(Transaction transaction, Message message);

 6: }

 7: internal abstract class TransactionInfo

 8: {

 9: //其他成员

 10: public abstract Transaction UnmarshalTransaction();

 11: }

如果采用不同事务处理协议，相同的事务需要按照不同的方式进行格式化，所以WCF事务体系内部创建了继承自TransactionFormatter的三个具体的TransactionFormatter类型：OleTxTransactionFormatter、WsatTransactionFormatter10和WsatTransactionFormatter11，它们分别对应于WCF支持的三种事务处理协议：OleTx、WS-AT 1.0和WS-AT 1.1。

我想很多人很想知道一个Transaction对象被不同的TransactionFormatter写入到Message对象后，Message具有怎样的格式呢？接下来我们通过一个简单的实例来演示。 三、实例演示：通过TransactionFormatter进行事务的写入

本实例是一个简单的控制台应用，我们将用它来演示模拟事务绑定是如何将当前事务写入消息。由于上面提到的TransactionFormatter和TransactionInfo都是内部类型，我们只能通过反射的方式使用它们。为此，我写了一个简单的工具类型ReflectUtil，用于通过反射的方式创建对象和调用某个方法，原理很简单，在这里就不多作介绍了。

 2: {

 3: public static object CreateInstance(string typeAssemblyQName, params object[] parameters)

 4: {

 5: Type typeofInstance = Type.GetType(typeAssemblyQName);

 6: BindingFlags bindingFlags = BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic;

 7: return Activator.CreateInstance(typeofInstance, bindingFlags, null, parameters, null);

 8: }

 9: public static object Invoke(string methodName, object targetInstance, params object[] parameters)

 10: {

 11: BindingFlags bindingFlags = BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.Public;

 12: return targetInstance.GetType().GetMethod(methodName, bindingFlags).Invoke(targetInstance, parameters);

 13: }

 14: }

然后我们创建我们自己的TransactionFormatter类型，它具有相同的方法ReadTransaction和WriteTransaction，ReadTransaction的返回类型直接使Transaction。相应的事务协议通过构造函数指定，事务协议决定了最终创建的真正TransactionFormatter的类型。真正的TransactionFormatter通过ReflectUtil创建，相应的方法也通过ReflectUtil调用。

 2: {

 3: const string OleTxFormatterType = "System.ServiceModel.Transactions.OleTxTransactionFormatter,System.ServiceModel, Version=3.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089";

 4: const string Wsat10FormatterType = "System.ServiceModel.Transactions.WsatTransactionFormatter10,System.ServiceModel, Version=3.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089";

 5: const string Wsat11FormatterType = "System.ServiceModel.Transactions.WsatTransactionFormatter11,System.ServiceModel, Version=3.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089";

 6: 

 7: public object InternalFormatter

 8: { get; private set; }

 9:  

 10: public TransactionFormatter(TransactionProtocol transactionProtocol)

 11: {

 12: if (transactionProtocol == TransactionProtocol.OleTransactions)

 13: {

 14: this.InternalFormatter = ReflectUtil.CreateInstance(OleTxFormatterType);

 15: }

 16: else if (transactionProtocol == TransactionProtocol.WSAtomicTransactionOctober2004)

 17: {

 18: this.InternalFormatter = ReflectUtil.CreateInstance(Wsat10FormatterType);

 19: }

 20: else

 21: {

 22: this.InternalFormatter = ReflectUtil.CreateInstance(Wsat11FormatterType);

 23: }

 24: }

 25:  

 26: public Transaction ReadTransaction(Message message)

 27: {

 28: object transInfo = ReflectUtil.Invoke("ReadTransaction", this.InternalFormatter, message);

 29: return ReflectUtil.Invoke("UnmarshalTransaction", transInfo) as Transaction;

 30: }

 31:  

 32: public void WriteTransaction(Transaction transaction, Message message)

 33: {

 34: ReflectUtil.Invoke("WriteTransaction", this.InternalFormatter, transaction, message);

 35: }

 36: }

然后我们基于三种不同的事务处理协议创建了相应的TransactionFormatter对象，并将相同的Transaction对象写入到一个Message对象中，并且Message的主体部分为Transaction对象本身。最终的Message对象被写入到3个XML文文件中。

 2: {

 3: using (TransactionScope transactionScope = new TransactionScope())

 4: {

 5: WriteTransaction(TransactionProtocol.OleTransactions, Transaction.Current, "oletx.xml");

 6: WriteTransaction(TransactionProtocol.WSAtomicTransactionOctober2004, Transaction.Current, "wsat10.xml");

 7: WriteTransaction(TransactionProtocol.WSAtomicTransaction11, Transaction.Current, "wsat11.xml");

 8: }

 9: }

 10:  

 11: static void WriteTransaction(TransactionProtocol transactionProtocol, Transaction transaction, string fileName)

 12: {

 13: string action = string.Format("http://www.artech.com/transactionformat/{0}", transactionProtocol.GetType().Name);

 14: Message message = Message.CreateMessage(MessageVersion.Default, action, Transaction.Current);

 15: TransactionFormatter formatter = new TransactionFormatter(transactionProtocol);

 16: formatter.WriteTransaction(Transaction.Current, message);

 17: using (XmlWriter writer = new XmlTextWriter(fileName, Encoding.UTF8))

 18: {

 19: message.WriteMessage(writer);

 20: }

 21: Process.Start(fileName);

 22: }

程序成功运行后，你将会得到三个表示Message对象的XML文件，它们的内容如下。有兴趣的读者可以结合相应事务处理协议规范，认真分析一下对应消息的结构，相信可以加深你对事务处理协议的理解。

OleTx.xml（OleTx）

 1: s:Envelope xmlns:a="http://www.w3.org/2005/08/addressing" xmlns:s="http://www.w3.org/2003/05/soap-envelope" 

 2: s:Header 

 3: a:Action s:mustUnderstand="1" http://www.artech.com/transactionformat/OleTransactionsProtocol /a:Action 

 4: OleTxTransaction s:mustUnderstand="1" d3p1:Expires="59392" xmlns:d3p1="http://schemas.xmlsoap.org/ws/2004/10/wscoor" xmlns="http://schemas.microsoft.com/ws/2006/02/tx/oletx" 

 5: PropagationToken AQAAAAMAAADknHb/v0zMQKhDZHfsF0Y1AAAQAAAAAACEAAAAAMW2bRzFtm00W6xnBOMYAHfXuW00W6xnTOQYADi1JADAu1YAkOMYADg5YjE0NzZkLTE2ZmYtNGI4MS05ZjEwLTE5MDE3ZTkwYjU1MgBiWWwMAAAAZM1kzSEAAABKSU5OQU4tVklTVEEAAAAAHAAAAEoASQBOAE4AQQBOAC0AVgBJAFMAVABBAAAAAAABAAAAAAAAABMAAAB0aXA6Ly9KaW5uYW4tVmlzdGEvAA== /PropagationToken 

 6: /OleTxTransaction 

 7: /s:Header 

 8: s:Body 

 9: Transaction xmlns:i="http://www.w3.org/2001/XMLSchema-instance" xmlns:x="http://www.w3.org/2001/XMLSchema" xmlns:d3p3="http://schemas.datacontract.org/2004/07/System.Transactions.Oletx" z:FactoryType="d3p3:OletxTransaction" xmlns:z="http://schemas.microsoft.com/2003/10/Serialization/" xmlns="http://schemas.datacontract.org/2004/07/System.Transactions" 

 10: OletxTransactionPropagationToken i:type="x:base64Binary" xmlns="" AQAAAAMAAADknHb/v0zMQKhDZHfsF0Y1AAAQAAAAAACEAAAAAMW2bRzFtm00W6xnBOMYAHfXuW00W6xnTOQYADi1JADAu1YAkOMYADg5YjE0NzZkLTE2ZmYtNGI4MS05ZjEwLTE5MDE3ZTkwYjU1MgDRiGgMAAAAZM1kzSEAAABKSU5OQU4tVklTVEEAAAAAHAAAAEoASQBOAE4AQQBOAC0AVgBJAFMAVABBAAAAAAABAAAAAAAAABMAAAB0aXA6Ly9KaW5uYW4tVmlzdGEvAA== /OletxTransactionPropagationToken 

 11: /Transaction 

 12: /s:Body 

 13: /s:Envelope 

 1: s:Envelope xmlns:a="http://www.w3.org/2005/08/addressing" xmlns:s="http://www.w3.org/2003/05/soap-envelope" 

 2: s:Header 

 3: a:Action s:mustUnderstand="1" http://www.artech.com/transactionformat/ WSAtomicTransactionOctober2004Protocol /a:Action 

 4: CoordinationContext s:mustUnderstand="1" xmlns:mstx="http://schemas.microsoft.com/ws/2006/02/transactions" xmlns="http://schemas.xmlsoap.org/ws/2004/10/wscoor" 

 5: wscoor:Identifier xmlns:wscoor="http://schemas.xmlsoap.org/ws/2004/10/wscoor" urn:uuid:ff769ce4-4cbf-40cc-a843-6477ec174635 /wscoor:Identifier 

 6: Expires 59392 /Expires 

 7: CoordinationType http://schemas.xmlsoap.org/ws/2004/10/wsat /CoordinationType 

 8: RegistrationService 

 9: Address xmlns="http://schemas.xmlsoap.org/ws/2004/08/addressing" https://jinnan-vista/WsatService/Registration/Coordinator/ / /Address 

 10: ReferenceParameters xmlns="http://schemas.xmlsoap.org/ws/2004/08/addressing" 

 11: mstx:RegisterInfo 

 12: mstx:LocalTransactionId ff769ce4-4cbf-40cc-a843-6477ec174635 /mstx:LocalTransactionId 

 13: /mstx:RegisterInfo 

 14: /ReferenceParameters 

 15: /RegistrationService 

 16: mstx:IsolationLevel 0 /mstx:IsolationLevel 

 17: mstx:LocalTransactionId ff769ce4-4cbf-40cc-a843-6477ec174635 /mstx:LocalTransactionId 

 18: PropagationToken xmlns="http://schemas.microsoft.com/ws/2006/02/tx/oletx" AQAAAAMAAADknHb/v0zMQKhDZHfsF0Y1AAAQAAAAAACEAAAAAMW2bRzFtm00W6xnBOMYAHfXuW00W6xnTOQYADi1JADAu1YAkOMYADg5YjE0NzZkLTE2ZmYtNGI4MS05ZjEwLTE5MDE3ZTkwYjU1MgDtiGgMAAAAZM1kzSEAAABKSU5OQU4tVklTVEEAAAAAHAAAAEoASQBOAE4AQQBOAC0AVgBJAFMAVABBAAAAAAABAAAAAAAAABMAAAB0aXA6Ly9KaW5uYW4tVmlzdGEvAA== /PropagationToken 

 19: /CoordinationContext 

 20: /s:Header 

 21: s:Body 

 22: Transaction xmlns:i="http://www.w3.org/2001/XMLSchema-instance" xmlns:x="http://www.w3.org/2001/XMLSchema" xmlns:d3p3="http://schemas.datacontract.org/2004/07/System.Transactions.Oletx" z:FactoryType="d3p3:OletxTransaction" xmlns:z="http://schemas.microsoft.com/2003/10/Serialization/" xmlns="http://schemas.datacontract.org/2004/07/System.Transactions" 

 23: OletxTransactionPropagationToken i:type="x:base64Binary" xmlns="" AQAAAAMAAADknHb/v0zMQKhDZHfsF0Y1AAAQAAAAAACEAAAAAMW2bRzFtm00W6xnBOMYAHfXuW00W6xnTOQYADi1JADAu1YAkOMYADg5YjE0NzZkLTE2ZmYtNGI4MS05ZjEwLTE5MDE3ZTkwYjU1MgAAAAAMAAAAZM1kzSEAAABKSU5OQU4tVklTVEEAJVwAHAAAAEoASQBOAE4AQQBOAC0AVgBJAFMAVABBAAAA//8BAAAAAAAAABMAAAB0aXA6Ly9KaW5uYW4tVmlzdGEvAA== /OletxTransactionPropagationToken 

 24: /Transaction 

 25: /s:Body 

 26: /s:Envelope 

 1: s:Envelope xmlns:a="http://www.w3.org/2005/08/addressing" xmlns:s="http://www.w3.org/2003/05/soap-envelope" 

 2: s:Header 

 3: a:Action s:mustUnderstand="1" http://www.artech.com/transactionformat/WSAtomicTransaction11Protocol /a:Action 

 4: CoordinationContext s:mustUnderstand="1" xmlns:mstx="http://schemas.microsoft.com/ws/2006/02/transactions" xmlns="http://docs.oasis-open.org/ws-tx/wscoor/2006/06" 

 5: wscoor:Identifier xmlns:wscoor="http://docs.oasis-open.org/ws-tx/wscoor/2006/06" urn:uuid:ff769ce4-4cbf-40cc-a843-6477ec174635 /wscoor:Identifier 

 6: Expires 59392 /Expires 

 7: CoordinationType http://docs.oasis-open.org/ws-tx/wsat/2006/06 /CoordinationType 

 8: RegistrationService 

 9: a:Address https://jinnan-vista/WsatService/Registration/Coordinator11 /a:Address 

 10: a:ReferenceParameters 

 11: mstx:RegisterInfo 

 12: mstx:LocalTransactionId ff769ce4-4cbf-40cc-a843-6477ec174635 /mstx:LocalTransactionId 

 13: /mstx:RegisterInfo 

 14: /a:ReferenceParameters 

 15: /RegistrationService 

 16: mstx:IsolationLevel 0 /mstx:IsolationLevel 

 17: mstx:LocalTransactionId ff769ce4-4cbf-40cc-a843-6477ec174635 /mstx:LocalTransactionId 

 18: PropagationToken xmlns="http://schemas.microsoft.com/ws/2006/02/tx/oletx" AQAAAAMAAADknHb/v0zMQKhDZHfsF0Y1AAAQAAAAAACEAAAAAMW2bRzFtm00W6xnBOMYAHfXuW00W6xnTOQYADi1JADAu1YAkOMYADg5YjE0NzZkLTE2ZmYtNGI4MS05ZjEwLTE5MDE3ZTkwYjU1MgAAMAAMAAAAZM1kzSEAAABKSU5OQU4tVklTVEEAAGwAHAAAAEoASQBOAE4AQQBOAC0AVgBJAFMAVABBAAAAbgABAAAAAAAAABMAAAB0aXA6Ly9KaW5uYW4tVmlzdGEvAA== /PropagationToken 

 19: /CoordinationContext 

 20: /s:Header 

 21: s:Body 

 22: Transaction xmlns:i="http://www.w3.org/2001/XMLSchema-instance" xmlns:x="http://www.w3.org/2001/XMLSchema" xmlns:d3p3="http://schemas.datacontract.org/2004/07/System.Transactions.Oletx" z:FactoryType="d3p3:OletxTransaction" xmlns:z="http://schemas.microsoft.com/2003/10/Serialization/" xmlns="http://schemas.datacontract.org/2004/07/System.Transactions" 

 23: OletxTransactionPropagationToken i:type="x:base64Binary" xmlns="" AQAAAAMAAADknHb/v0zMQKhDZHfsF0Y1AAAQAAAAAACEAAAAAMW2bRzFtm00W6xnBOMYAHfXuW00W6xnTOQYADi1JADAu1YAkOMYADg5YjE0NzZkLTE2ZmYtNGI4MS05ZjEwLTE5MDE3ZTkwYjU1MgDRiGgMAAAAZM1kzSEAAABKSU5OQU4tVklTVEEAAAAAHAAAAEoASQBOAE4AQQBOAC0AVgBJAFMAVABBAAAAAAABAAAAAAAAABMAAAB0aXA6Ly9KaW5uYW4tVmlzdGEvAA== /OletxTransactionPropagationToken 

 24: /Transaction 

 25: /s:Body 

 26: /s:Envelope 

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