Compensator Class

 

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

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

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

public class Compensator : ServicedComponent

NameDescription
System_CAPS_pubmethodCompensator()

Initializes a new instance of the Compensator class.

NameDescription
System_CAPS_pubpropertyClerk

Gets a value representing the Compensating Resource Manager (CRM) Clerk object.

NameDescription
System_CAPS_pubmethodAbortRecord(LogRecord)

Delivers a log record to the Compensating Resource Manager (CRM) Compensator during the abort phase.

System_CAPS_protmethodActivate()

Called by the infrastructure when the object is created or allocated from a pool. Override this method to add custom initialization code to objects.(Inherited from ServicedComponent.)

System_CAPS_pubmethodBeginAbort(Boolean)

Notifies the Compensating Resource Manager (CRM) Compensator of the abort phase of the transaction completion, and the upcoming delivery of records.

System_CAPS_pubmethodBeginCommit(Boolean)

Notifies the Compensating Resource Manager (CRM) Compensator of the commit phase of the transaction completion and the upcoming delivery of records.

System_CAPS_pubmethodBeginPrepare()

Notifies the Compensating Resource Manager (CRM) Compensator of the prepare phase of the transaction completion and the upcoming delivery of records.

System_CAPS_protmethodCanBePooled()

This method is called by the infrastructure before the object is put back into the pool. Override this method to vote on whether the object is put back into the pool.(Inherited from ServicedComponent.)

System_CAPS_pubmethodCommitRecord(LogRecord)

Delivers a log record in forward order during the commit phase.

System_CAPS_protmethodConstruct(String)

Called by the infrastructure just after the constructor is called, passing in the constructor string. Override this method to make use of the construction string value.(Inherited from ServicedComponent.)

System_CAPS_pubmethodCreateObjRef(Type)

Creates an object that contains all the relevant information required to generate a proxy used to communicate with a remote object.(Inherited from MarshalByRefObject.)

System_CAPS_protmethodDeactivate()

Called by the infrastructure when the object is about to be deactivated. Override this method to add custom finalization code to objects when just-in-time (JIT) compiled code or object pooling is used.(Inherited from ServicedComponent.)

System_CAPS_pubmethodDispose()

Releases all resources used by the ServicedComponent.(Inherited from ServicedComponent.)

System_CAPS_protmethodDispose(Boolean)

Releases the unmanaged resources used by the ServicedComponent and optionally releases the managed resources.(Inherited from ServicedComponent.)

System_CAPS_pubmethodEndAbort()

Notifies the Compensating Resource Manager (CRM) Compensator that it has received all the log records available during the abort phase.

System_CAPS_pubmethodEndCommit()

Notifies the Compensating Resource Manager (CRM) Compensator that it has delivered all the log records available during the commit phase.

System_CAPS_pubmethodEndPrepare()

Notifies the Compensating Resource Manager (CRM) Compensator that it has had all the log records available during the prepare phase.

System_CAPS_pubmethodEquals(Object)

Determines whether the specified object is equal to the current object.(Inherited from Object.)

System_CAPS_protmethodFinalize()

Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.(Inherited from Object.)

System_CAPS_pubmethodGetHashCode()

Serves as the default hash function. (Inherited from Object.)

System_CAPS_pubmethodGetLifetimeService()

Retrieves the current lifetime service object that controls the lifetime policy for this instance.(Inherited from MarshalByRefObject.)

System_CAPS_pubmethodGetType()

Gets the Type of the current instance.(Inherited from Object.)

System_CAPS_pubmethodInitializeLifetimeService()

Obtains a lifetime service object to control the lifetime policy for this instance.(Inherited from MarshalByRefObject.)

System_CAPS_protmethodMemberwiseClone()

Creates a shallow copy of the current Object.(Inherited from Object.)

System_CAPS_protmethodMemberwiseClone(Boolean)

Creates a shallow copy of the current MarshalByRefObject object.(Inherited from MarshalByRefObject.)

System_CAPS_pubmethodPrepareRecord(LogRecord)

Delivers a log record in forward order during the prepare phase.

System_CAPS_pubmethodToString()

Returns a string that represents the current object.(Inherited from Object.)

NameDescription
System_CAPS_pubinterfaceSystem_CAPS_privmethodIRemoteDispatch.RemoteDispatchAutoDone(String)

This API supports the product infrastructure and is not intended to be used directly from your code. Ensures that, in the COM+ context, the ServicedComponent class object's done bit is set to true after a remote method invocation.(Inherited from ServicedComponent.)

System_CAPS_pubinterfaceSystem_CAPS_privmethodIRemoteDispatch.RemoteDispatchNotAutoDone(String)

This API supports the product infrastructure and is not intended to be used directly from your code. Does not ensure that, in the COM+ context, the ServicedComponent class object's done bit is set to true after a remote method invocation.(Inherited from ServicedComponent.)

System_CAPS_pubinterfaceSystem_CAPS_privmethodIServicedComponentInfo.GetComponentInfo(Int32, String[])

This API supports the product infrastructure and is not intended to be used directly from your code. Obtains certain information about the ServicedComponent class instance.(Inherited from 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
    }    

}

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();
        }

    }

}

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();
        }

    }

}

.NET Framework
Available since 1.1

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

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