The OSGi EventAdmin service is described in the OSGi Compendium and OSGi Enterprise specifications in Chapter 113, Event Admin Service Specification. It provides a means to use a publish and subscribe mechanism to send events that may be targeted at a particular topic and may contain an arbitrary number of event properties.

Event topics are text names that are used to identify where the event will be delivered. They are represented with a slash (/) separating parts of the name, for example, org/osgi/framework/ServiceEvent or org/osgi/service/log/LogEntry.

An Event is an immutable object, initialized from a Dictionary or Map, which has a number of properties. These properties can store user-specific data, along with a number of other (potentially null) standard properties from the EventConstants class: