1.2. Consumer Client Scenario
Overview
In the consumer client scenario, the consumer client receives messages directly from the broker, as soon as they become available. This approach requires the consumer client to implement a callback object, which exposes a Web service endpoint. Figure 1.1, “A Consumer Client Scenario” provides an overview of this scenario.
Figure 1.1. A Consumer Client Scenario
Clients in this scenario
There are two clients involved in this scenario:
- Publisher client—generates notification messages and publishes the messages on a specific topic, by sending them to the notification broker.
- Consumer client—a client that implements a consumer callback object (exposing a Web service endpoint of
NotificationConsumertype), which is capable of receiving notifications directly from the notification broker.
Scenario steps
In this scenario, a consumer client receives notification messages from the broker as follows:
- The consumer client instantiates a consumer callback object, which implements the
NotificationConsumerinterface and is capable of receiving notifications from the broker. - The consumer client creates a subscription by invoking the
subscribeoperation on the broker, passing the following operation arguments:- Topic name—specifies the topic that the client wants to subscribe to.
- Callback reference—a reference to the consumer callback object that will receive the notifications, where the service reference has the format of a WS-Addressing Endpoint Reference (EPR).
- A publisher client sends a notification message on a specific topic, by invoking the
notifyoperation on the broker. - If the message topic matches the consumer client's subscription, the broker will forward the message to the consumer client by invoking the
notifyoperation on the consumer callback service.
