Chapter 5. Plugin Development

The class declaration should look like this (assuming you are implementing just the packet processor):

public class Message extends AnnotatedXMPPProcessor
   implements XMPPProcessorIfc

The first thing to create is the plugin ID. This is a unique string which you put in the configuration file to tell the server to load and use the plugin. In most cases you can use XMLNS if the plugin wants packets with elements with a very specific name space. Of course there is no guarantee there is no other packet for this specific XML element too. As we want to process all messages and don’t want to spend whole day on thinking about a cool ID, let’s say our ID is: message.

A plugin informs about it’s presence using a static ID field and @Id annotation placed on class:

@Id(ID)
public class Message extends AnnotatedXMPPProcessor
   implements XMPPProcessorIfc {
  protected static final String ID = "message";
}

As mentioned before, this plugin receives only this kind of packets for processing which it is interested in. In this example, the plugin is interested only in packets with <message/> elements and only if they are in the "jabber:client" namespace. To indicate all supported elements and namespaces we have to add 2 more annotations:

@Id(ID)
@Handles({
  @Handle(path={ "message" },xmlns="jabber:client")
})
public class Message extends AnnotatedXMPPProcessor
   implements XMPPProcessorIfc {
  private static final String ID = "message";
}

The class declaration should look like this (assuming you are implementing just the packet processor):

public class Message extends XMPPProcessor
   implements XMPPProcessorIfc

The first thing to create is the plugin ID like above.

A plugin informs about it’s ID using following code:

private static final String ID = "message";
public String id() { return ID; }

As mentioned before this plugin receives only this kind of packets for processing which it is interested in. In this example, the plugin is interested only in packets with <message/> elements and only if they are in "jabber:client" namespace. To indicate all supported elements and namespaces we have to add 2 more methods:

public String[] supElements() {
  return new String[] {"message"};
}

public String[] supNamespaces()	{
  return new String[] {"jabber:client"};
}

Now we have our plugin prepared for loading in Tigase. The next step is the actual packet processing method. For the complete code, please refer to the plugin in the Git. I will only comment here on elements which might be confusing or add a few more lines of code which might be helpful in your case.

@Override
public void process(Packet packet, XMPPResourceConnection session,
	NonAuthUserRepository repo, Queue<Packet> results, Map<String, Object> settings)
	throws XMPPException {

	// For performance reasons it is better to do the check
	// before calling logging method.
	if (log.isLoggable(Level.FINEST)) {
		log.log(Level.FINEST, "Processing packet: {0}", packet);
	}

	// You may want to skip processing completely if the user is offline.
	if (session == null) {
		return;
	}    // end of if (session == null)

	try {

		// Remember to cut the resource part off before comparing JIDs
		BareJID id = (packet.getStanzaTo() != null) ? packet.getStanzaTo().getBareJID() : null;

		// Checking if this is a packet TO the owner of the session
		if (session.isUserId(id)) {

			// Yes this is message to 'this' client
			Packet result = packet.copyElementOnly();

			// This is where and how we set the address of the component
			// which should receive the result packet for the final delivery
			// to the end-user. In most cases this is a c2s or Bosh component
			// which keep the user connection.
			result.setPacketTo(session.getConnectionId(packet.getStanzaTo()));

			// In most cases this might be skipped, however if there is a
			// problem during packet delivery an error might be sent back
			result.setPacketFrom(packet.getTo());

			// Don't forget to add the packet to the results queue or it
			// will be lost.
			results.offer(result);

			return;
		}    // end of else

		// Remember to cut the resource part off before comparing JIDs
		id = (packet.getStanzaFrom() != null) ? packet.getStanzaFrom().getBareJID() : null;

		// Checking if this is maybe packet FROM the client
		if (session.isUserId(id)) {

			// This is a packet FROM this client, the simplest action is
			// to forward it to its destination:
			// Simple clone the XML element and....
			// ... putting it to results queue is enough
			results.offer(packet.copyElementOnly());

			return;
		}

		// Can we really reach this place here?
		// Yes, some packets don't even have from or to address.
		// The best example is IQ packet which is usually a request to
		// the server for some data. Such packets may not have any addresses
		// And they usually require more complex processing
		// This is how you check whether this is a packet FROM the user
		// who is owner of the session:
		JID jid = packet.getFrom();

		// This test is in most cases equal to checking getElemFrom()
		if (session.getConnectionId().equals(jid)) {

			// Do some packet specific processing here, but we are dealing
			// with messages here which normally need just forwarding
			Element el_result = packet.getElement().clone();

			// If we are here it means FROM address was missing from the
			// packet, it is a place to set it here:
			el_result.setAttribute("from", session.getJID().toString());

			Packet result = Packet.packetInstance(el_result, session.getJID(),
				packet.getStanzaTo());

			// ... putting it to results queue is enough
			results.offer(result);
		}
	} catch (NotAuthorizedException e) {
		log.warning("NotAuthorizedException for packet: " + packet);
		results.offer(Authorization.NOT_AUTHORIZED.getResponseMessage(packet,
				"You must authorize session first.", true));
	}    // end of try-catch
}