Processing Incoming Packets

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.PacketFilter 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.PacketFilter filter = new AndFilter(new PacketTypeFilter(Message.class),         new FromContainsFilter("[e-mail]"));// 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 Packet Filters

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

• PacketTypeFilter -- filters for packets that are a particular Class type.
• PacketIDFilter -- 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.
• PacketExtensionFilter -- 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.