COM & .NET Component Services

Combining JITA with Object Pooling

The two instance management techniques provided by COM+ are not mutually exclusive. JITA and object pooling can be combined in a very powerful way. Using both object pooling and JITA on the same component is useful in situations when object initialization is both generic (not client specific) and expensive. Thus, using just JITA would not make sense; when you have no control over the length of time, the object’s client keeps its reference to the object, so you would realize marginal gain from object pooling. When you configure your object to use both, instead of creating and releasing the object on each method call, COM+ grabs an object from the pool and returns the object to the pool after the method completes its execution. The JITA aspects are still maintained because the object instance will be torn away from its client. The pool will also be used on every method call, not just on CoCreate and Release calls from the client. Implementing IObjectControl is optional, but I strongly recommend it. As always, a call to IObjectControl::Activate( ) marks entry to a context, and a call to IObjectControl::Deactivate( ) marks an exit. COM+ calls IObjectControl::CanBePooled( ) after every Deactivate( ), letting the object decide whether it wants to be recycled or destroyed. This life cycle is shown in Figure 3-9. When you configure your component to support both JITA and object pooling, COM+ deactivates the object every time the done bit is set and returns ...