ASP.NET创建Web服务之使用事务

支持XML Web服务的事务利用公共语言运行期中的支持,其是基于Microsoft Transaction Server ( MTS)和COM+ Services中相同的分布式事务模型。该模型基于明确的判断一个对象是否参与一个事务,而不是编写特定的代码用来处理委托和回调一个事务。对于一个使用ASP.NET创建的XML Web服务,你可以通过设置其应用到一个XML Web服务方法上的WebMethod属性的TransactionOption属性来声明一个XML Web服务的事务行为。如果该XML Web服务方法执行的时候抛出一个异常,那么该事务自动地结束;相反,如果没有发生异常,该事务自动委托。

WebMethod属性的TransactionOption属性规定一个XML Web服务方法如何参与一个事务。虽然这个声明级别表示一个事务逻辑,但是它是消除实际事务的一个步骤。当事物对象访问数据源(如数据库或消息队列)时实际事务产生。关联该对象的事务自动流向适当的资源管理程序。像.NET Framework Data Provider(用于SQL Server或OLE DB)这样的.NET Framework数据提供者在对象的上下文中查找事务并通过Distributed Transaction Coordinator (DTC,分布式事务协调程序)编目事务。全部的事务自动产生。

XML Web服务方法只能参与一个作为新事务的根的事务。作为一个新事务的根,所有的与资源管理器(像运行Microsoft SQL Server、Microsoft Message Queuing和Microsoft Host Integration Server的服务器)的相互作用维护需要运行健壮的分布式应用程序的ACID性质。调用其他的XML Web服务方法的XML Web服务方法参与不同的事务,因为事务不流经XML Web服务方法。

使用来自XML Web服务方法的事务

声明一个XML Web服务。

[C#]

1@ WebService Language="C#" Class="Orders" 

[Visual Basic]

1@ WebService Language="VB" Class="Orders" 

把一个汇编指令加到System.EnterpriseServices上。

1@ Assembly name="System.EnterpriseServices,Version=1.0.3300.0,Culture=neutral,PublicKeyToken=b03f5f7f11d50a3a" 

添加引用到System.Web.Services和System.EnterpriseServices域名空间。

[C#]
using System.Web.Services;
using System.EnterpriseServices;
[Visual Basic]
Imports System.Web.Services
Imports System.EnterpriseServices

声明一个XML Web服务方法,设置WebMethod属性的TransactionOption属性为TransactionOption.RequiresNew。

[C#]
[ WebMethod(TransactionOption=TransactionOption.RequiresNew)]
public int DeleteAuthor(string lastName)
[Visual Basic]
< WebMethod(TransactionOption:=TransactionOption.RequiresNew)> _
Public Function DeleteAuthor(lastName As String) As Integer

下面的代码示例显示一个使用单个XML Web服务方法的XML Web服务,调用DeleteDatabase。这个XML Web服务方法执行一个事务范围内的数据库操作。如果该数据库操作抛出一个异常,该事务自动地停止;否则,该事务自动地委托。

[C#]

1@ WebService Language="C#" Class="Orders" 
1@ Assembly name="System.EnterpriseServices,Version=1.0.3300.0,Culture=neutral,PublicKeyToken=b03f5f7f11d50a3a" 

using System;
using System.Data;
using System.Data.SqlClient;
using System.Web.Services;
using System.EnterpriseServices;

public class Orders : WebService
{
[ WebMethod(TransactionOption=TransactionOption.RequiresNew)]
public int DeleteAuthor(string lastName)
{
String deleteCmd = "DELETE FROM authors WHERE au_lname='" +
lastName + "'" ;
String exceptionCausingCmdSQL = "DELETE FROM NonExistingTable WHERE
au_lname='" + lastName + "'" ;

SqlConnection sqlConn = new SqlConnection(
"Persist Security Info=False;Integrated Security=SSPI;database=pubs;server=myserver");

SqlCommand deleteCmd = new SqlCommand(deleteCmdSQL,sqlConn);
SqlCommand exceptionCausingCmd = new
SqlCommand(exceptionCausingCmdSQL,sqlConn);

// This command should execute properly.
deleteCmd.Connection.Open();
deleteCmd.ExecuteNonQuery();

// This command results in an exception, so the first command is
// automatically rolled back. Since the XML Web service method is
// participating in a transaction, and an exception occurs, ASP.NET
// automatically aborts the transaction. The deleteCmd that
// executed properly is rolled back.

int cmdResult = exceptionCausingCmd.ExecuteNonQuery();

sqlConn.Close();

return cmdResult;
}
}
[Visual Basic]

1@ WebService Language="VB" Class="Orders" 
1@ assembly name="System.EnterpriseServices" 

Imports System
Imports System.Data
Imports System.Data.SqlClient
Imports System.Web.Services
Imports System.Web.Util
Imports System.EnterpriseServices

Public Class Orders

 1<webmethod(transactionoption:=transactionoption.requiresnew)> _   
 2Public Function DeleteAuthor (lastName as String) as Integer 
 3
 4Dim deleteCmdSQL As String = "DELETE FROM authors WHERE au_lname='" + _   
 5lastName + "'"   
 6Dim exceptionCausingCmdSQL As String = "DELETE FROM " + _   
 7"NonExistingTable WHERE au_lname='" + lastName + "'" 
 8
 9Dim sqlConn As SqlConnection = New SqlConnection( _   
10"Persist Security Info=False;Integrated Security=SSPI;database=pubs;server=myserver") 
11
12Dim deleteCmd As SqlCommand = New SqlCommand(deleteCmdSQL,sqlConn)   
13Dim exceptionCausingCmd As SqlCommand = New _   
14SqlCommand(exceptionCausingCmdSQL,sqlConn) 
15
16' This command should execute properly.   
17deleteCmd.Connection.Open()   
18deleteCmd.ExecuteNonQuery() 
19
20' This command results in an exception, so the first command is   
21' automatically rolled back. Since the XML Web service method is   
22' participating in a transaction, and an exception occurs, ASP.NET   
23' automatically aborts the transaction. The deleteCmd that   
24' executed properly is rolled back. 
25
26Dim cmdResult As Integer = exceptionCausingCmd.ExecuteNonQuery()   
27sqlConn.Close() 
28
29Return cmdResult   
30End Function   
31End Class</webmethod(transactionoption:=transactionoption.requiresnew)>
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