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Compensator Class

Represents the base class for all Compensating Resource Manager (CRM) Compensators.

Namespace: System.EnterpriseServices.CompensatingResourceManager
Assembly: System.EnterpriseServices (in system.enterpriseservices.dll)

'Declaration
Public Class Compensator
	Inherits ServicedComponent
'Usage
Dim instance As Compensator

public class Compensator extends ServicedComponent
public class Compensator extends ServicedComponent

The user should extend from this object in order to write a custom transaction Compensator.

A Compensator must always have a public constructor; otherwise, the recovery engine cannot create it.

For more information, see How to: Create a Compensating Resource Manager (CRM).

The following code example demonstrates the use of this class.

' A CRM Compensator

Public Class AccountCompensator
    Inherits Compensator
    
    Private receivedPrepareRecord As Boolean = False
    
    
    Public Overrides Sub BeginPrepare() 
    
    End Sub 'BeginPrepare
    
    ' nothing to do
    Public Overrides Function PrepareRecord(ByVal log As LogRecord) As Boolean 
        
        ' Check the validity of the record.
        If log Is Nothing Then
            Return True
        End If
        Dim record As [Object]() = log.Record
        
        If record Is Nothing Then
            Return True
        End If
        If record.Length <> 2 Then
            Return True
        End If 
        ' The record is valid.
        receivedPrepareRecord = True
        Return False
    
    End Function 'PrepareRecord
    
    Public Overrides Function EndPrepare() As Boolean 
        ' Allow the transaction to proceed onlyif we have received a prepare record.
        If receivedPrepareRecord Then
            Return True
        Else
            Return False
        End If
    
    End Function 'EndPrepare
    
    Public Overrides Sub BeginCommit(ByVal commit As Boolean) 
    
    End Sub 'BeginCommit
    
    ' nothing to do
    Public Overrides Function CommitRecord(ByVal log As LogRecord) As Boolean 
        ' nothing to do
        Return False
    
    End Function 'CommitRecord
    
    Public Overrides Sub EndCommit() 
    
    End Sub 'EndCommit
    
    ' nothing to do
    Public Overrides Sub BeginAbort(ByVal abort As Boolean) 
    
    End Sub 'BeginAbort
    
    ' nothing to do
    Public Overrides Function AbortRecord(ByVal log As LogRecord) As Boolean 
        
        ' Check the validity of the record.
        If log Is Nothing Then
            Return True
        End If
        Dim record As [Object]() = log.Record
        
        If record Is Nothing Then
            Return True
        End If
        If record.Length <> 2 Then
            Return True
        End If 
        ' Extract old account data from the record.
        Dim filename As String = CStr(record(0))
        Dim balance As Integer = Fix(record(1))
        
        ' Restore the old state of the account.
        AccountManager.WriteAccountBalance(filename, balance)
        
        Return False
    
    End Function 'AbortRecord
    
    Public Overrides Sub EndAbort() 
    
    End Sub 'EndAbort
End Class 'AccountCompensator ' nothing to do

// A CRM Compensator
public class AccountCompensator extends Compensator
{
    private boolean receivedPrepareRecord = false;

    public void BeginPrepare()
    {
        // nothing to do
    } //BeginPrepare    

    public boolean PrepareRecord(LogRecord log)
    {
        // Check the validity of the record.
        if (log == null) {
            return true;
        }
        Object record[] = new Object[] { log.get_Record() };

        if (record == null) {
            return true;
        }
        if (record.get_Length() != 2) {
            return true;
        }
        // The record is valid.
        receivedPrepareRecord = true;
        return false;
    } //PrepareRecord

    public boolean EndPrepare()
    {
        // Allow the transaction to proceed onlyif we have received
        // a prepare record.
        if (receivedPrepareRecord) {
            return true;
        }
        else {
            return false;
        }
    } //EndPrepare

    public void BeginCommit(boolean commit)
    {
        // nothing to do
    } //BeginCommit    

    public boolean CommitRecord(LogRecord log)
    {
        // nothing to do
        return false;
    } //CommitRecord

    public void EndCommit()
    {
        // nothing to do
    } //EndCommit    

    public void BeginAbort(boolean abort)
    {
        // nothing to do
    } //BeginAbort   

    public boolean AbortRecord(LogRecord log)
    {
        // Check the validity of the record.
        if (log == null) {
            return true;
        }
        Object record[] = new Object[] { log.get_Record() };

        if (record == null) {
            return true;
        }
        if (record.get_Length() != 2) {
            return true;
        }
        // Extract old account data from the record.
        String fileName = (String)(record.get_Item(0));
        int balance = System.Convert.ToInt32(record[1]);

        // Restore the old state of the account.
        AccountManager.WriteAccountBalance(fileName, balance);

        return false;
    } //AbortRecord

    public void EndAbort()
    {
        // nothing to do
    } //EndAbort
} //AccountCompensator 

This compensator is used by the following worker class.

' A CRM Worker
<Transaction()>  _
Public Class Account
    Inherits ServicedComponent
    
    ' A data member for the account file name.
    Private filename As String
    
    
    Public Property Filenam() As String
        Get
            Return Filename
        End Get
        Set(ByVal value As String)
            filename = Value
        End Set
    End Property
    
    
    ' A boolean data member that determines whether to commit or abort the transaction.
    Private commit As Boolean
    
    
    Public Property AllowCommit() As Boolean 
        Get
            Return commit
        End Get
        Set
            commit = value
        End Set
    End Property
    
    
    
    
    ' Debit the account, 
    Public Sub DebitAccount(ByVal ammount As Integer) 
        
        ' Create a new clerk using the AccountCompensator class.
        Dim clerk As New Clerk(GetType(AccountCompensator), "An account transaction compensator", CompensatorOptions.AllPhases)
        ' Create a record of previous account status, and deliver it to the clerk.
        Dim balance As Integer = AccountManager.ReadAccountBalance(Filenam)
        
        Dim record(1) As [Object]
        record(0) = filename
        record(1) = balance
        
        clerk.WriteLogRecord(record)
        clerk.ForceLog()
        ' Perform the transaction
        balance -= ammount
        AccountManager.WriteAccountBalance(filename, balance)
        
        ' Commit or abort the transaction 
        If commit Then
            ContextUtil.SetComplete()
        Else
            ContextUtil.SetAbort()
        End If
    
End Class 'Account


// A CRM Worker
/** @attribute Transaction()
 */
public class Account extends ServicedComponent
{
    // A data member for the account file name.
    /** @property 
     */
    private String fileName;
    
    public String get_fileName()
    {
        return fileName;
    } //get_fileName
    
    public void set_fileName(String value)
    {
        fileName = value;
    } //set_fileName

    // A boolean data member that determines whether to commit or
    // abort the transaction.
    private boolean commit;

    /** @property 
     */
    public boolean get_AllowCommit()
    {
        return commit;
    } //get_AllowCommit

    /** @property 
     */
    public void set_AllowCommit(boolean value)
    {
        commit = value;
    } //set_AllowCommit

    // Debit the account, 
    public void DebitAccount(int ammount)
    {
        // Create a new clerk using the AccountCompensator class.
        Clerk clerk = new Clerk(AccountCompensator.class.ToType(),
            "An account transaction compensator",
            CompensatorOptions.AllPhases);

        // Create a record of previous account status, and deliver
        // it to the clerk.
        Console.WriteLine("filename = " + fileName);
        int balance = AccountManager.ReadAccountBalance(fileName);

        Object record[] = new Object[2];
        record.set_Item(0, fileName);
        record.set_Item(1,(Int32)balance);

        clerk.WriteLogRecord(record);
        clerk.ForceLog();

        // Perform the transaction
        balance -= ammount;
        AccountManager.WriteAccountBalance(fileName, balance);

        // Commit or abort the transaction 
        if (commit) {
            ContextUtil.SetComplete();
        }
        else {
            ContextUtil.SetAbort();
        }
    } //DebitAccount 
} //Account

The following code example demonstrates a client that exercises this compensator and worker.

Imports System



Public Class CrmClient
    
    
    Public Shared Sub Main() 
        
        ' Create a new account object. The object is created in a COM+ server application.
        Dim account As New Account()
        
        ' Transactionally debit the account.
        Try
            account.Filenam = System.IO.Path.GetFullPath("JohnDoe")
            account.AllowCommit = True
            account.DebitAccount(3)
        Finally
            account.Dispose()
        End Try
    
    End Sub 'Main 
End Class 'CrmClient


import System.*;

public class CrmClient
{
    public static void main(String[] args)
    {
        // Create a new account object. The object is created in a COM+
        // server application.
        Account account = new Account();

        // Transactionally debit the account.
        try {
            account.set_fileName(System.IO.Path.GetFullPath("JohnDoe"));
            account.set_AllowCommit(true);
            account.DebitAccount(3);
        }
        finally {
            account.Dispose();
        }
    } //main
} //CrmClient 

System.Object
   System.MarshalByRefObject
     System.ContextBoundObject
       System.EnterpriseServices.ServicedComponent
        System.EnterpriseServices.CompensatingResourceManager.Compensator

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 98, Windows 2000 SP4, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.

.NET Framework

Supported in: 2.0, 1.1, 1.0

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