| Platform SDK: Transaction Server |
[This product will work only on Windows NT 4.0 versions and earlier. For Windows 2000 and later, see COM+ (Component Services).]
Each MTS object has an associated context object. A context object is an extensible MTS object that provides context for the execution of an instance, including transaction, activity, and security properties. When an MTS object is created, MTS automatically creates a context object for it. When the MTS object is released, MTS automatically releases the context object.
An MTS object and its associated context object
An MTS object's context has intrinsic properties that are determined during object creation. These properties include the identity of the client that initiated the object's creation and whether or not the object executes within the scope of a transaction.
The properties established for the new object context are determined by a combination of:
If your application uses Microsoft Internet Information Server (IIS), you can retrieve IIS intrinsic objects as follows:
For more information on IIS intrinsic objects, see the IIS documentation.
Contexts Are Implicit
MTS maintains an implicit relationship between an MTS object and its context. This feature eliminates the need for you to pass explicitly a context object through your application.
You can access an MTS object's context by calling the GetObjectContext function. This function returns a reference to the IObjectContext interface. Resource dispensers and other context-aware services can also access the object's context. This permits the ODBC resource dispenser automatically to enlist connections on the object's transaction.
Before a method of an MTS object is dispatched for execution, that object's context becomes the current context for the thread. This context remains current as long as the object remains within the context. Calling a method in a different context causes that context to become current; the caller's context is automatically restored on return from the method.
Managing References to the Context Object
You must not pass a reference to the context object outside the object. You must explicitly release every reference that you acquire on the object context.
The context object is not available during calls to the component's class factory. This means, for example, that a Visual C++ class implementation cannot access a context object during calls to a constructor or destructor. Objects that require access to the context object during initialization or destruction should implement IObjectControl. For more information, see Deactivating Objects.