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Processing Incoming Stanzas

Back

Smack provides a flexible framework for processing incoming packets using two constructs:

  • org.jivesoftware.smack.PacketCollector -- a class that lets you synchronously wait for new packets.
  • org.jivesoftware.smack.PacketListener -- an interface for asynchronously notifying you of incoming packets. A packet listener is used for event style programming, while a packet collector has a result queue of packets that you can do polling and blocking operations on. So, a packet listener is useful when you want to take some action whenever a packet happens to come in, while a packet collector is useful when you want to wait for a specific packet to arrive. Packet collectors and listeners can be created using an XMPPConnection instance.

The org.jivesoftware.smack.filter.StanzaFilter interface determines which specific packets will be delivered to a PacketCollector or PacketListener. Many pre-defined filters can be found in the org.jivesoftware.smack.filter package.

The following code snippet demonstrates registering both a packet collector and a packet listener:

// Create a packet filter to listen for new messages from a particular
// user. We use an AndFilter to combine two other filters._
StanzaFilter filter = new AndFilter(new StanzaTypeFilter(Message.class),
		new FromContainsFilter("[email protected]"));
// Assume we've created an XMPPConnection name "connection".

// First, register a packet collector using the filter we created.
PacketCollector myCollector = connection.createPacketCollector(filter);
// Normally, you'd do something with the collector, like wait for new packets.

// Next, create a packet listener. We use an anonymous inner class for brevity.
PacketListener myListener = new PacketListener() {
		**public** **void** processPacket(Packet packet) {
			// Do something with the incoming packet here._
		}
	};
// Register the listener._
connection.addPacketListener(myListener, filter);

Standard Stanza Filters

A rich set of packet filters are included with Smack, or you can create your own filters by coding to the StanzaFilter interface. The default set of filters includes:

  • StanzaTypeFilter -- filters for packets that are a particular Class type.
  • StanzaIdFilter -- filters for packets with a particular packet ID.
  • ThreadFilter -- filters for message packets with a particular thread ID.
  • ToContainsFilter -- filters for packets that are sent to a particular address.
  • FromContainsFilter -- filters for packets that are sent to a particular address.
  • StanzaExtensionFilter -- filters for packets that have a particular packet extension.
  • AndFilter -- implements the logical AND operation over two filters.
  • OrFilter -- implements the logical OR operation over two filters.
  • NotFilter -- implements the logical NOT operation on a filter.

Copyright (C) Jive Software 2002-2008