Release 10.1A: OpenEdge Development:
Messaging and ESB

Consuming messages

A Message Consumer consumes messages either asynchronously or synchronously. The message consumption type is set for a session. Messages are processed by the Message Consumer when the 4GL is in a WAIT–FOR state or other IO-blocking state. While the application is in such a state, all other UI and non-UI events are handled normally. WAIT–FOR can be called explicitly by the 4GL code. It can also be called through the waitForMessages procedure on the Session object, which works the same for GUI, character, batch, AppServer, and WebSpeed applications. Once a message is consumed, the content of the message is inaccessible.

The following sections describe:

Creating a Message Consumer object
Creating a message handler process
Setting reply properties
Receiving messages from a queue
Subscribing to a topic
Terminating the Message Consumer object
Processing messages
Controlling flow of messages
Reusing messages
Message-reception issues
Reply mechanisms