Smack/documentation/developer/stanzas.md

PacketExtension

The static from(Packet) Method

Every PacketExtension class must have a static from() method that retrieves that extension for a given Stanza (if any).

Sample Code

public static RSMSet from(Packet) {
  return packet.getExtension(ELEMENT, NAMESPACE);
}

Sometimes certain PacketExtension's are only found in one stanza type, in that case, specify the parameter type. For example public static CarbonExtension getFrom(Message).