5.1. The configuration problem

Before we look into how to configure a service in OSGi, you should understand why and when configuration is needed. To do this, we’ll use an example—the Notification Broker service.

5.1.1. The Notification Broker service

A notification system allows an application to send events of interest to another application. Such a system typically consists of three main components or services: a publisher, a broker, and a subscriber. The notification subscriber registers filters in the notification broker; these filters are sometimes called event criteria. The notification publisher sends events to the notification broker, which dispatches those events that match the criteria to the registered subscribers, as shown in figure 5.1.