Article ID: 174261
Article Last Modified on 8/21/2007
APPLIES TO
- Microsoft Message Queue Server 1.0
This article was previously published under Q174261
SUMMARY
With Microsoft Message Queuing Server it's possible to send the state of COM objects supporting the IPersistStream or IPersistStorage interface. This article discusses what is necessary to take advantage of this feature using Visual C++ and ATL.
MORE INFORMATION
The following files are available for download from the Microsoft Download Center:
For additional information about how to download Microsoft Support files, click the following article number to view the article in the Microsoft Knowledge Base:
119591 How to Obtain Microsoft Support Files from Online Services
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Designing the Object Whose State Will Be Sent Over a Queue
The sample has two ActiveX components, Point and Line, which are implemented using ATL and Visual C++. In addition to the code generated by the ATL wizard, some additional lines have to be added for IPersistStream implementation. An object that implements IPersistStream is ready for sending its state over a MSMQ's queue.
For additional information, click the article number below to view the article in the Microsoft Knowledge Base:
194179 SAMPLE: AtlEvnt.exe Creates ATL Sinks Using IDispEventImpl
Sending the Objects State Over the Queue
We use the #import directive in Visual C++ to manipulate the MSQM COM and the Point and Line objects. For additional information on how to initialize OLE when using the #import directive, please see the following article in the Microsoft Knowledge Base:
169496 INFO: Using ActiveX Data Objects (ADO) via #import in VC++"
The following code shows the declaration for the various ActiveX components used. The data types are defined in the compiler generated files Mqoa.tlh, Mqoa.tli, GraphObj.tlh, and GraphObj.tli:
// For these ActiveX components we need only smart interface pointer
IMSMQQueueInfosPtr pQueueInfos;
IMSMQQueueInfoPtr pQueueInfo;
IMSMQQueuePtr pQueue;
IUnknownPtr pIUnknown;
// Instantiate the following ActiveX components
IMSMQQueryPtr pQuery(__uuidof(MSMQQuery));
IMSMQMessagePtr pMessage(__uuidof(MSMQMessage));
ILinePtr pLine(__uuidof(Line));
IPointPtr pPoint(__uuidof(Point));
Sending object state requires a pointer to the IUnknown interface. The MSMQMessage component uses this interface to ask the object for the IPersistStream interface. The object's IUnknown interface pointer must be stored in a VARIANT and could then be assigned to the body property of the MSMQMessage object:
...
if (n == 1) {
// Initialize point object
pPoint->x = 8;
pPoint->y = 9;
// The message body gets the IUnknown pointer
pMessage->Body = static_cast<IUnknown*>(pPoint);
} else {
...
}
pMessage->Send(pQueue);
...
Receiving the Objects State from the Queue
When an MSMQMessage instructs an ActiveX component to save its state to a stream, it also asks the component to save its CLSID to the stream. When receiving an object state, this enables the Microsoft Message Queue Server to instantiate the ActiveX component belonging to the transmitted CLSID.
The message body property of the received message actually is a VARIANT containing an IUnknown pointer to the interface of newly created object. Now it's up to the program to determine which object state was received and which object was created. One way to do this is to ask the IUnknown for ILine or the IPoint interface.
...
// Get the next message
pMessage = pQueue->Receive();
IPointPtr pPoint((IUnknown*)pMessage->Body);
// Check if it's a Point object
if (pPoint != NULL) {
cout << "\nGot a Point Object: " << pPoint->x << " " << \
pPoint->y << "\n";
}
else {
ILinePtr pLine((IUnknown*)pMessage->Body);
// Check if it's a Line object
if (pLine != NULL) {
cout << "\nGot a Line Object: " << pLine->x1 << " "
<< \ pLine->y1 << " " << pLine->x2 << " " << pLine->y2 << "\n";
}
else
cout << "\nUnknown Object !!!\n";
}
pQueue->Close();
...
The complete sample source is provided. To compile the project you need Visual C++ 5.0
REFERENCES
MSMQ Online SDK help file
For additional information, click the article number below to view the article in the Microsoft Knowledge Base:
194179 SAMPLE: AtlEvnt.exe Creates ATL Sinks Using IDispEventImpl
(c) Microsoft Corporation 1997, All Rights Reserved. Contributions by Michael Zill, Microsoft Corporation
Additional query words: MQPers
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