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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)

public class Compensator : ServicedComponent
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 : Compensator
{

    private bool receivedPrepareRecord = false;

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

    public override bool PrepareRecord (LogRecord log)
    {

        // Check the validity of the record.
        if (log == null) return(true);
        Object[] record = log.Record as Object[];
        if (record == null) return(true);
        if (record.Length != 2) return(true);

        // The record is valid.
        receivedPrepareRecord = true;
        return(false);              
    }

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

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

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

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

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

    public override bool AbortRecord (LogRecord log)
    {

        // Check the validity of the record.
        if (log == null) return(true);
        Object[] record = log.Record as Object[];
        if (record == null) return(true);
        if (record.Length != 2) return(true);

        // Extract old account data from the record.
        string filename = (string) record[0];
        int balance = (int) record[1];
 
        // Restore the old state of the account.
        AccountManager.WriteAccountBalance(filename, balance);

        return(false);
    }

    public override void EndAbort ()
    {
        // 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 : ServicedComponent
{

    // A data member for the account file name.
    private string filename;
    
    public string Filename
    {
        get
        {
            return(filename);
        }
        set
        {
            filename = value;
        }
    }


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

    public bool AllowCommit
    {
        get
        {
            return(commit);
        }
        set
        {
            commit = value;
        }
    }



    // Debit the account, 
    public void DebitAccount (int ammount)
    {

        // Create a new clerk using the AccountCompensator class.
        Clerk clerk = new Clerk(typeof(AccountCompensator),
          "An account transaction compensator", CompensatorOptions.AllPhases);

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

	Object[] record = new Object[2];
	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)
        {
            ContextUtil.SetComplete();
        }
        else
        {
            ContextUtil.SetAbort();
        }
      
    }

}

// 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.

using System;

public class CrmClient
{

    public static void Main ()
    {

        // Create a new account object. The object is created in a COM+ server application.
        Account account = new Account();

        // Transactionally debit the account.
        try
        {
            account.Filename = System.IO.Path.GetFullPath("JohnDoe");
            account.AllowCommit = true;
            account.DebitAccount(3);
        }
        finally
        {
            account.Dispose();
        }
          
    }

}

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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