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.NET实用技巧—NHibernate分布式事务

作者：刘冬 编辑： 胡铭娅 2010-07-30 17:47 来源：刘冬的博客
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      【IT168 技术应用】我们已实现了在同一应用程序下的分布式事务——即多Dao层+同Service层，每个Dao对应一个数据库，一个Service调用多个Dao。但是在一些特定的子系统较多的项目中，开发人员是无法访问到某个子系统的数据库，这就意味着不能通过增加Dao层来实现分布式事务。正如一个银行的软件系统，记录了客户的账户信息和存款金额，北京的分公司和上海的分公司分别有自己的数据库和软件系统。现在，要实现北京的系统向上海的系统转账，然而各自作为开发人员来说，没有足够的权限去访问对方的数据库，但是可以提供Web Service的方式去访问其系统服务。这样，我们就需要实现基于Web Service的分布式事务。

　　实现基于Web Service的分布式事务的方法比较多，可以通过.NET企业服务的方式。但是为了更好的实现，我们选择WCF作为一个分布式应用程序框架。WCF在实现分布式事务中有它的优越之处。其思路在于启动MSDTC服务，将客户端的事务以流的方式传递到服务器端，在服务器端执行通过时，客户端再提交事务，相反则回滚事务。

　　我们模仿上篇的场景做一个demo，并使用上篇的Dao和Domain。

　　一、启动MSDTC服务。

　　二、Service层

　　①.Customer

  public interface ICustomerManager
    {
        CustomerInfo Get(object id);

        object Save(CustomerInfo entity);

        void Update(CustomerInfo entity);
    }

    public class CustomerManager : ICustomerManager
    {
        private ICustomerDao Dao { get; set; }

        public CustomerInfo Get(object id)
        {
            return Dao.Get(id);
        }

        public object Save(CustomerInfo entity)
        {
            return Dao.Save(entity);
        }

        public void Update(CustomerInfo entity)
        {
            if (entity.Money > 3000)
            {
                throw new Exception("订金上限");
            }
            Dao.Update(entity);
        }
    }
<?xml version="1.0" encoding="utf-8" ?>
<objects xmlns="http://www.springframework.net">

  <object id="transactionManager"
        type="Spring.Data.NHibernate.HibernateTransactionManager, Spring.Data.NHibernate21">
    <property name="DbProvider" ref="DbProvider"/>
    <property name="SessionFactory" ref="NHibernateSessionFactory"/>
  </object>

  <object id="transactionInterceptor" type="Spring.Transaction.Interceptor.TransactionInterceptor, Spring.Data">
    <property name="TransactionManager" ref="transactionManager"/>
    <property name="TransactionAttributeSource">
      <object type="Spring.Transaction.Interceptor.AttributesTransactionAttributeSource, Spring.Data"/>
    </property>
  </object>

  <object id="BaseTransactionManager"  type="Spring.Transaction.Interceptor.TransactionProxyFactoryObject, Spring.Data" abstract="true">
    <property name="PlatformTransactionManager" ref="transactionManager"/>
    <property name="TransactionAttributes">
      <name-values>  
        <add key="*" value="PROPAGATION_REQUIRED"/>
      </name-values>
    </property>
  </object>

  <object id="Customer.CustomerManager" parent="BaseTransactionManager">
    <property name="Target">
      <object type="Customer.Service.Implement.CustomerManager, Customer.Service">
        <property name="Dao" ref="Customer.CustomerDao"/>
      </object>
    </property>
  </object>

</objects>

 

　　②.Order

  public interface IOrderManager
    {
        object Save(OrderInfo entity);
    }

    public class OrderManager : IOrderManager
    {
        public IOrderDao Dao { get; set; }

        public object Save(OrderInfo entity)
        {
            return Dao.Save(entity);
        }
    }
<?xml version="1.0" encoding="utf-8" ?>
<objects xmlns="http://www.springframework.net">

  <object id="transactionManager"
        type="Spring.Data.NHibernate.HibernateTransactionManager, Spring.Data.NHibernate21">
    <property name="DbProvider" ref="DbProvider"/>
    <property name="SessionFactory" ref="NHibernateSessionFactory"/>
  </object>

  <object id="transactionInterceptor" type="Spring.Transaction.Interceptor.TransactionInterceptor, Spring.Data">
    <property name="TransactionManager" ref="transactionManager"/>
    <property name="TransactionAttributeSource">
      <object type="Spring.Transaction.Interceptor.AttributesTransactionAttributeSource, Spring.Data"/>
    </property>
  </object>

  <object id="BaseTransactionManager"  type="Spring.Transaction.Interceptor.TransactionProxyFactoryObject, Spring.Data" abstract="true">
    <property name="PlatformTransactionManager" ref="transactionManager"/>
    <property name="TransactionAttributes">
      <name-values>  
        <add key="*" value="PROPAGATION_REQUIRED"/>
      </name-values>
    </property>
  </object>

  <object id="Order.OrderManager" parent="BaseTransactionManager">
    <property name="Target">
      <object type="Order.Service.Implement.OrderManager, Order.Service">
        <property name="Dao" ref="Order.OrderDao"/>
      </object>
    </property>
  </object>

</objects>

　　三、服务契约和Host。

　　1、契约

　　作为服务契约，需要启用Session，并且设置TransactionFlowOption的等级为Allowed或Mandatory来接收客户端事务流。

　　作为契约的实现部分，需要设置TransactionScopeRequired为true来启用事务作用域。

　　①.Customer

[ServiceContract(SessionMode = SessionMode.Required)]
    public interface ICustomerContract
    {
        [OperationContract]
        [TransactionFlow(TransactionFlowOption.Allowed)]
        CustomerInfo Get(object id);

        [OperationContract]
        [TransactionFlow(TransactionFlowOption.Allowed)]
        object Save(CustomerInfo entity);

        [OperationContract]
        [TransactionFlow(TransactionFlowOption.Allowed)]
        void Update(CustomerInfo entity);
    }

    [AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Required)]
    public class CustomerServer : ICustomerContract
    {
        public ICustomerManager Manager { get; set; }

        [OperationBehavior(TransactionScopeRequired = true)]
        public CustomerInfo Get(object id)
        {
            return Manager.Get(id);
        }

        [OperationBehavior(TransactionScopeRequired = true)]
        public object Save(CustomerInfo entity)
        {

            return Manager.Save(entity);
        }

        [OperationBehavior(TransactionScopeRequired = true)]
        public void Update(CustomerInfo entity)
        {
            Manager.Update(entity);
        }

 　　②.Order

[ServiceContract(SessionMode = SessionMode.Required)]
    public interface IOrderContract
    {
        [OperationContract]
        [TransactionFlow(TransactionFlowOption.Allowed)]
        object Save(OrderInfo entity);
    }

   [AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Required)]
    public class OrderServer : IOrderContract
    {
        public IOrderManager Manager { get; set; }

        [OperationBehavior(TransactionScopeRequired = true)]
        public object Save(OrderInfo entity)
        {
            return Manager.Save(entity);
        }
    }


 　　2、配置

　　然而，Spring.NET针对NHibernate的Session管理使用的是OSIV模式(Open Session In View)，即使用httpModule去拦截HTTP请求，在每次请求开始时打开Session作用域(SessionScope)，最后在请求结束后关闭SessionScope。这样一来，在客户端每请求一次时都会打开SessionScope，在请求结束会关闭SessionScope，然后当请求结束后再去处理分布式就会提示“无法使用已释放对象”的错误。所以说，OSIV是无法正常管理分布式事务的。出于上述原因，我们决定在Global.asax的配置，在Session(这里的Session是ASP.NET中的Session)启动时候打开SessionScope，在Session结束时关闭SessionScope。这样分布式事务就会与SessionScope同步了。

　　最后，在配置appSettings节点增加

　　另外配置WCF的binding时需要选择一种支持Session的binding(如wsHttpBinding)并且将binding中的transactionFlow属性设置为true。

public class Global : System.Web.HttpApplication
    {

        protected void Application_Start(object sender, EventArgs e)
        {
            log4net.Config.XmlConfigurator.Configure();
        }

        protected void Session_Start(object sender, EventArgs e)
        {
            SessionScope sessionScope = new SessionScope("appSettings", typeof(SessionScope), false);
            sessionScope.Open();
            HttpContext.Current.Session["SessionScope"] = sessionScope;
        }

        
        protected void Session_End(object sender, EventArgs e)
        {
            SessionScope sessionScope = HttpContext.Current.Session["SessionScope"] as SessionScope;
            if (sessionScope != null)
            {
                sessionScope.Close();
            }
        }

    }

 　　①.Customer

<?xml version="1.0" encoding="utf-8"?>
<configuration>

  
<%@ ServiceHost Language="C#" Debug="true" Service="Customer.Host" Factory="Spring.ServiceModel.Activation.ServiceHostFactory"%>

 

　　②.Order

<?xml version="1.0" encoding="utf-8"?>
<configuration>

  ..........

  <!--spring配置-->
  <spring xmlns="http://www.springframework.net">
    <parsers>
      <parser type="Spring.Data.Config.DatabaseNamespaceParser, Spring.Data" />
      <parser type="Spring.Transaction.Config.TxNamespaceParser, Spring.Data" />
    </parsers>
    <context>
      <resource uri="config://spring/objects" />

      <!--Dao-->
      <resource uri="assembly://Order.Dao/Order.Dao.Config/Dao.xml" />
      <!--Service-->
      <resource uri="assembly://Order.Service/Order.Service.Config/Service.xml" />

    </context>
    <objects xmlns="http://www.springframework.net"
             xmlns:aop="http://www.springframework.net/aop">

      <object id="Order.Host" type="Order.Host.Implement.OrderServer, Order.Host">
        <property name="Manager" ref="Order.OrderManager" />
      </object>

    </objects>
  </spring>

  <appSettings>
    <add key="Spring.Data.NHibernate.Support.SessionScope.SessionFactoryObjectName" value="NHibernateSessionFactory"/>
  </appSettings>

  <system.web>
    <compilation debug="true" targetFramework="4.0" />

    <httpModules>
      <add name="Spring" type="Spring.Context.Support.WebSupportModule, Spring.Web" />
    </httpModules>

  </system.web>
  <system.serviceModel>
    <services>
      <service name="Order.Host">
        <endpoint address="" binding="wsHttpBinding" bindingConfiguration="ServerBinding" contract="Order.Host.IOrderContract"/>
        <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange"/>
      </service>
    </services>
    <bindings>
      <wsHttpBinding >
        <binding name="ServerBinding" transactionFlow="true"  >
        </binding>
      </wsHttpBinding>
    </bindings>
    <behaviors>
      <serviceBehaviors>
        <behavior>
          <!-- 为避免泄漏元数据信息，请在部署前将以下值设置为 false 并删除上面的元数据终结点 -->
          <serviceMetadata httpGetEnabled="true"/>
          <!-- 要接收故障异常详细信息以进行调试，请将以下值设置为 true。在部署前设置为 false 以避免泄漏异常信息 -->
          <serviceDebug includeExceptionDetailInFaults="true"/>
        </behavior>
      </serviceBehaviors>
    </behaviors>
    <serviceHostingEnvironment multipleSiteBindingsEnabled="true" aspNetCompatibilityEnabled="true"/>
  </system.serviceModel>
<system.webServer>
    <modules runAllManagedModulesForAllRequests="true"/>
  </system.webServer>
  
</configuration>

<%@ ServiceHost Language="C#" Debug="true" Service="Order.Host" Factory="Spring.ServiceModel.Activation.ServiceHostFactory"%>

 　　四、客户端

[TestFixture]
    public class HostTest
    {
        private CustomerContractClient customerProxy;

        private OrderContractClient orderProxy;

        [SetUp]
        public void Init()
        {
            customerProxy = new CustomerContractClient();
            orderProxy = new OrderContractClient();
        }

        [Test]
        public void InitData()
        {
            using (TransactionScope scope = new TransactionScope())
            {
                customerProxy.Save(new CustomerInfo
                {
                    Name = "刘冬"
                });

                scope.Complete();
            }
        }

        [Test]
        public void DistributedTransactionTest()
        {
            using (TransactionScope scope = new TransactionScope())
            {
                try
                {
                    CustomerInfo customer = customerProxy.Get(1);
                    orderProxy.Save(new OrderInfo
                    {
                        Address = "中国北京",
                        CustomerId = (int)customer.ID,
                        OrderDate = DateTime.Now
                    });
                    customer.Money += 1000;
                    customerProxy.Update(customer);
                    scope.Complete();
                    Console.WriteLine("分布式事务已提交");
                }
                catch (Exception ex)
                {
                    Transaction.Current.Rollback();
                    Console.WriteLine("发送错误：分布式事务已回滚");
                }
            }
        }
    }

  

　　五、运行效果

　　1.初始化数据

　　2.建立第一张订单，订金小于3000

　　3.建立第一张订单，订金小于3000

　　4.建立第一张订单，订金等于3000

　　5.建立第一张订单，订金大于3000，事务回滚。


 

　　好了，基于Web Service的分布式事务已经实现了。

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