深入分析WCF事务投票实现方式

我们知道事务是通过参与方进行WCF事务投票(Voting)来决定 "提交(Complete)" 或者 "回滚(Rollback)" 操作的。默认情况下,WCF 通过 OperationBehavior(TransactionAutoComplete = true) 来完成投票动作。(TransactionAutoComplete = true 是缺省值,不需要显式声明。)

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我们将服务方法默认的 TransactionAutoComplete=true 改为 false,看看结果 。

 
 
 
  1. // ---- Service1 -----
  2. [ServiceContract(SessionModeSessionMode=SessionMode.Required)]
  3. public interface IService1
  4. {
  5. [OperationContract]
  6. [TransactionFlow(TransactionFlowOption.Allowed)]
  7. void Test();
  8. }
  9. public class MyService1 : IService1
  10. {
  11. [OperationBehavior(TransactionScopeRequired=true, 
    TransactionAutoComplete=false)]
  12. public void Test()
  13. {
  14. string connStr = "server=(local);uid=sa;pwd=sa;database=temp";
  15. using (SqlConnection conn = new SqlConnection(connStr))
  16. {
  17. conn.Open();
  18. SqlCommand cmd = new SqlCommand("insert into [User] 
    ([name]) values (@name)", 
  19. conn);
  20. cmd.Parameters.Add(new SqlParameter("@name", "ZhangSan"));
  21. cmd.ExecuteNonQuery();
  22. }
  23. }
  24. }
  25. // ---- Service2 -----
  26. [ServiceContract(SessionMode = SessionMode.Required)]
  27. public interface IService2
  28. {
  29. [OperationContract]
  30. [TransactionFlow(TransactionFlowOption.Allowed)]
  31. void Test();
  32. }
  33. public class MyService2 : IService2
  34. {
  35. [OperationBehavior(TransactionScopeRequired = true, 
    TransactionAutoComplete = false)]
  36. public void Test()
  37. {
  38. string connStr = "server=(local);uid=sa;pwd=sa;database=temp";
  39. using (SqlConnection conn = new SqlConnection(connStr))
  40. {
  41. conn.Open();
  42. SqlCommand cmd = new SqlCommand("insert into Account ([user], 
    [money]) values (@user, @money)", 
  43. conn);
  44. cmd.Parameters.Add(new SqlParameter("@user", "ZhangSan"));
  45. cmd.Parameters.Add(new SqlParameter("@money", 100));
  46. cmd.ExecuteNonQuery();
  47. }
  48. }
  49. }
  50. public class WcfTest
  51. {
  52. public static void Test()
  53. {
  54. // ---- Host -----
  55. AppDomain.CreateDomain("Server").DoCallBack(delegate
  56. {
  57. NetTcpBinding bindingServer = new NetTcpBinding();
  58. bindingServer.TransactionFlow = true;
  59. ServiceHost host1 = new ServiceHost(typeof(MyService1), 
    new Uri("net.tcp://localhost:8080"));
  60. host1.AddServiceEndpoint(typeof(IService1), bindingServer, "");
  61. host1.Open();
  62. ServiceHost host2 = new ServiceHost(typeof(MyService2), 
    new Uri("net.tcp://localhost:8081"));
  63. host2.AddServiceEndpoint(typeof(IService2), bindingServer, "");
  64. host2.Open();
  65. });
  66. // ---- Client -----
  67. NetTcpBinding bindingClient = new NetTcpBinding();
  68. bindingClient.TransactionFlow = true;
  69. IService1 client1 = ChannelFactory.CreateChannel(bindingClient, 
  70. new EndpointAddress("net.tcp://localhost:8080"));
  71. IService2 client2 = ChannelFactory.CreateChannel(bindingClient, 
  72. new EndpointAddress("net.tcp://localhost:8081"));
  73. using (TransactionScope scope = new TransactionScope())
  74. {
  75. try
  76. {
  77. client1.Test();
  78. client2.Test();
  79. scope.Complete();
  80. }
  81. finally
  82. {
  83. (client1 as IDisposable).Dispose();
  84. (client2 as IDisposable).Dispose();
  85. }
  86. }
  87. }
  88. }

运行结果表明事务无法提交,触发 TransactionAbortedException 异常,显示 "事务终止"。那么除了默认被称之为 "声明投票(Declarative voting)" 的方式外,我们还能怎么做?OperationContext 有个 SetTransactionComplete() 方法,允许我们在代码中完成WCF事务投票行为。这种投票方式更加灵活,便于我们在代码中做出更多的控制,被称之为 "显式投票(Explicit voting)"。

在上面两个 Test() 方法的***一行,添加 "OperationContext.Current.SetTransactionComplete();",再次运行,事务被正确提交。

 
 
 
  1. [OperationBehavior(TransactionScopeRequired=true, 
    TransactionAutoComplete=false)]
  2. public void Test()
  3. {
  4. // ...
  5. OperationContext.Current.SetTransactionComplete();
  6. } 
  7. ...

接下来,我们设想另外一种情况。事务不由 Client 发起,在 Service1.Test() 调用 Service2.Test(),那么事务会是个什么样子呢?Service1、Service2 的参数 "OperationBehavior(TransactionScopeRequired = true)" 决定了如果没有外界传入的环境事务,那么会自动创建一个根事务。所以 Service1.Test() 会创建一个根事务,而 Service2.Test() 会参与这个事务。可问题在于 Service.Test() 中并没有显示调用 Transaction.Complete,事务能被提交吗?

 
 
 
  1. // ---- Service1 -----
  2. [ServiceContract]
  3. public interface IService1
  4. {
  5. [OperationContract]
  6. [TransactionFlow(TransactionFlowOption.Allowed)]
  7. void Test();
  8. }
  9. public class MyService1 : IService1
  10. {
  11. [OperationBehavior(TransactionScopeRequired=true)]
  12. public void Test()
  13. {
  14. string connStr = "server=(local);uid=sa;pwd=sa;database=temp";
  15. using (SqlConnection conn = new SqlConnection(connStr))
  16. {
  17. conn.Open();
  18. SqlCommand cmd = new SqlCommand("insert into [User] 
    ([name]) values (@name)", 
  19. conn);
  20. cmd.Parameters.Add(new SqlParameter("@name", "ZhangSan"));
  21. cmd.ExecuteNonQuery();
  22. }
  23. InvokeService2();
  24. }
  25. public void InvokeService2()
  26. {
  27. NetTcpBinding bindingClient = new NetTcpBinding();
  28. bindingClient.TransactionFlow = true;
  29. IService2 client2 = ChannelFactory.CreateChannel
    (bindingClient, 
  30. new EndpointAddress("net.tcp://localhost:8081"));
  31. using (client2 as IDisposable)
  32. {
  33. client2.Test();
  34. }
  35. }
  36. }
  37. // ---- Service2 -----
  38. [ServiceContract]
  39. public interface IService2
  40. {
  41. [OperationContract]
  42. [TransactionFlow(TransactionFlowOption.Allowed)]
  43. void Test();
  44. }
  45. public class MyService2 : IService2
  46. {
  47. [OperationBehavior(TransactionScopeRequired = true)]
  48. public void Test()
  49. {
  50. string connStr = "server=(local);uid=sa;pwd=sa;database=temp";
  51. using (SqlConnection conn = new SqlConnection(connStr))
  52. {
  53. conn.Open();
  54. SqlCommand cmd = new SqlCommand("insert into Account 
    ([user], [money]) values (@user, @money)", 
  55. conn);
  56. cmd.Parameters.Add(new SqlParameter("@user", "ZhangSan"));
  57. cmd.Parameters.Add(new SqlParameter("@money", 100));
  58. cmd.ExecuteNonQuery();
  59. }
  60. }
  61. }
  62. public class WcfTest
  63. {
  64. public static void Test()
  65. {
  66. // ---- Host -----
  67. AppDomain.CreateDomain("Server").DoCallBack(delegate
  68. {
  69. NetTcpBinding bindingServer = new NetTcpBinding();
  70. bindingServer.TransactionFlow = true;
  71. ServiceHost host1 = new ServiceHost(typeof(MyService1), 
    new Uri("net.tcp://localhost:8080"));
  72. host1.AddServiceEndpoint(typeof(IService1), bindingServer, "");
  73. host1.Open();
  74. ServiceHost host2 = new ServiceHost(typeof(MyService2), 
    new Uri("net.tcp://localhost:8081"));
  75. host2.AddServiceEndpoint(typeof(IService2), bindingServer, "");
  76. host2.Open();
  77. });
  78. // ---- Client -----
  79. NetTcpBinding bindingClient = new NetTcpBinding();
  80. bindingClient.TransactionFlow = true;
  81. IService1 client1 = ChannelFactory.CreateChannel
    (bindingClient, 
  82. new EndpointAddress("net.tcp://localhost:8080"));
  83. try
  84. {
  85. client1.Test();
  86. }
  87. finally
  88. {
  89. (client1 as IDisposable).Dispose();
  90. }
  91. }
  92. }

运行结果表明,事务被正确提交。看来这和客户端使用 TransactionScope 必须显式调用 Complete() 有所不同。同样,如果将 Service2.Test() 设为 TransactionAutoComplete=false,在不调用 "OperationContext.Current.SetTransactionComplete();" 的情况下,也会触发事务失败异常。

以上就是我们为大家介绍的WCF事务投票的相关实现方法。

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