Using Extensions

Getting Extensions from Stanzas

Extensions in stanzas can simply be retrieved in the following way:

DelayedDelivery delayedDelivery = message.getExtension(DelayedDelivery.class); // XEP-203

Attention attention = message.getExtension(Attention.class); // XEP-224

EntityCapabilities entityCapabilities = presence.getExtension(EntityCapabilities.class); // XEP-115

Managing Extensions

Most extensions need some kind of logic or have to implement business rules defined in the respective XEP.

Therefore extensions are associated with a Manager class, which handles their business rules.

Nearly all extensions have one thing in common: They can be either enabled or disabled, e.g. you can either enable or disable support for XEP-0115: Entity Capabilities or XEP-0184: Message Delivery Receipts.

Extensions are also associated with an identifier, usually a namespace, e.g. urn:xmpp:receipts.

By enabling an extension, support for it will be automatically advertised by XEP-0030: Service Discovery.

To get a manager for a specific extension, you use the getManager method of the XmppClient.

This allows you to enable/disable an extension, but also to configure behavior of the extension.

Examples

EntityTimeManager entityTimeManager = xmppClient.getManager(EntityTimeManager.class);
entityTimeManager.setEnabled(false);

This manager manages XEP-0202: Entity Time and is enabled by default. Inbound “time” requests are automatically replied to with the current time, while enabled.

SoftwareVersionManager softwareVersionManager = xmppClient.getManager(SoftwareVersionManager.class);
softwareVersionManager.setSoftwareVersion(new SoftwareVersion("Babbler", "1.0"));

If an entity requests your software version, this manager automatically replies with the specified version.

Managers usually also allow to interact with other entities, e.g. retrieving the time, software version, or last activity of another entity:

LastActivityManager lastActivityManager = xmppClient.getManager(LastActivityManager.class);
LastActivity lastActivity = lastActivityManager.getLastActivity(Jid.of("juliet@example.net")).getResult();

(This will get the last activity of the user, i.e. the last logout date.)

Enabling or Disabling Extensions

In order to enable or disable an extension, you can either use the approach described above (using the Manager class) or use a more convenient method:

xmppClient.enableFeature(EntityTimeManager.class);

or by providing the Extension namespace, e.g. urn:xmpp:time:

xmppClient.enableFeature(EntityTime.NAMESPACE);

In both cases, the extension will either be included or excluded from service discovery and the business logic of the extension will either be executed or not.