Compensator Class
Assembly: System.EnterpriseServices (in system.enterpriseservices.dll)
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.MarshalByRefObject
System.ContextBoundObject
System.EnterpriseServices.ServicedComponent
System.EnterpriseServices.CompensatingResourceManager.Compensator
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.