JBoss.org Community Documentation

2.4.5. Observing changes

The JCR API supports observing a repository to receive notifications of additions, changes and deletions of nodes and properties. The JBoss DNA federated repository will support this API through two primary means.

When the changes are made through the federated repository, the JBoss DNA federation engine is well aware of the set of changes that have been (or are being) made to the unified graph. These events are directly propagated to listeners.

Sources have the ability to publish events, making it possible for the JBoss DNA federation engine and clients that have registered listeners to be notified of changes in the information managed by that source. These events are first processed by the federation engine and possibly altered based upon contributions from other sources. (The federation engine also uses these events to update or purge information in the cache, which may add to the event set.) The resulting (and possibly altered) event set is then sent to all client listeners.