Sams Teach Yourself Microsoft® Windows® DNA Programming in 21 Days

Queued Components

COM requires an in-depth knowledge of marshaling in order to queue, send, receive, and process asynchronous messages. COM+ introduces Queued Components, which automatically marshal data in the form of a Microsoft Message Queue (MSMQ) message. Because Queued Components support is built-in support for transactions, a server failure will not result in inconsistent data. Overall, Queued Components allow objects to be invoked either synchronously or asynchronously without any special programming.

As seen in Figure 13.2, Queued Components consist of

Figure 13.2. Message flow for a Queued Component.

• Recorder

• Queue

• Listener

• Player

When ...