30. XMPP Support

Spring Integration provides Channel Adapters for XMPP.

30.1 Introduction

XMPP describes a way for multiple agents to communicate with each other in a distributed system. The canonical use case is to send and receive chat messages, though XMPP can be, and is, used for far more applications. XMPP is used to describe a network of actors. Within that network, actors may address each other directly, as well as broadcast status changes (e.g. "presence").

XMPP provides the messaging fabric that underlies some of the biggest Instant Messaging networks in the world, including Google Talk (GTalk) - which is also available from within GMail - and Facebook Chat. There are many good open-source XMPP servers available. Two popular implementations are Openfire and ejabberd

Spring integration provides support for XMPP via XMPP adapters which support sending and receiving both XMPP chat messages and presence changes from other entries in your roster. As with other adapters, the XMPP adapters come with support for a convenient namespace-based configuration. To configure the XMPP namespace, include the following elements in the headers of your XML configuration file:

xmlns:int-xmpp="http://www.springframework.org/schema/integration/xmpp"
xsi:schemaLocation="http://www.springframework.org/schema/integration/xmpp 
	http://www.springframework.org/schema/integration/xmpp/spring-integration-xmpp.xsd"

30.2 XMPP Connection

Before using inbound or outbound XMPP adapters to participate in the XMPP network, an actor must establish its XMPP connection. This connection object could be shared by all XMPP adapters connected to a particular account. Typically this requires - at a minimum - user, password, and host. To create a basic XMPP connection, you can utilize the convenience of the namespace.

<int-xmpp:xmpp-connection
  id="myConnection"
  user="user"
  password="password"
  host="host"
  port="port"
  resource="theNameOfTheResource"
  subscription-mode="accept_all"/>
      

[Note]Note
For added convenience you can rely on the default naming convention and omit the id attribute. The default name xmppConnection will be used for this connection bean.

If the XMPP Connection goes stale, reconnection attempts will be made with an automatic login as long as the previous connection state was logged (authenticated). We also register a ConnectionListener which will log connection events if the DEBUG logging level is enabled.

30.3 XMPP Messages

30.3.1 Inbound Message Channel Adapter

The Spring Integration adapters support receiving chat messages from other users in the system. To do this, the Inbound Message Channel Adapter "logs in" as a user on your behalf and receives the messages sent to that user. Those messages are then forwarded to your Spring Integration client. The payload of the inbound Spring Integration message may be of the raw type org.jivesoftware.smack.packet.Message, or of the type java.lang.String if you set the extract-payload attribute's value to 'true' when configuring an adapter. Configuration support for the XMPP Inbound Message Channel Adapter is provided via the inbound-channel-adapter element.

<int-xmpp:inbound-channel-adapter id="xmppInboundAdapter" 
	channel="xmppInbound" 
	xmpp-connection="testConnection" 
	extract-payload="false" 
	auto-startup="true"/>

As you can see amongst the usual attributes this adapter also requires a reference to an XMPP Connection.

It is also important to mention that the XMPP inbound adapter is an event driven adapter and a Lifecycle implementation. When started it will register a PacketListener that will listen for incoming XMPP Chat Messages. It forwards any received messages to the underlying adapter which will convert them to Spring Integration Messages and send them to the specified channel. It will unregister the PacketListener when it is stopped.

30.3.2 Outbound Message Channel Adapter

You may also send chat messages to other users on XMPP using the Outbound Message Channel Adapter. Configuration support for the XMPP Outbound Message Channel Adapter is provided via the outbound-channel-adapter element.

<int-xmpp:outbound-channel-adapter id="outboundEventAdapter" 
						channel="outboundEventChannel" 
						xmpp-connection="testConnection"/>

The adapter expects as its input - at a minimum - a payload of type java.lang.String, and a header value for XmppHeaders.CHAT_TO that specifies to which user the Message should be sent. To create a message you might use the following Java code:

Message<String> xmppOutboundMsg = MessageBuilder.withPayload("Hello, XMPP!" )
						.setHeader(XmppHeaders.CHAT_TO, "userhandle")
						.build();

Another mechanism of setting the header is by using the XMPP header-enricher support. Here is an example.

<int-xmpp:header-enricher input-channel="input" output-channel="output">
	<int-xmpp:chat-to value="test1@example.org"/>
</int-xmpp:header-enricher>

30.4 XMPP Presence

XMPP also supports broadcasting state. You can use this capability to let people who have you on their roster see your state changes. This happens all the time with your IM clients; you change your away status, and then set an away message, and everybody who has you on their roster sees your icon or username change to reflect this new state, and additionally might see your new "away" message. If you would like to receive notification, or notify others, of state changes, you can use Spring Integration's "presence" adapters.

30.4.1 Inbound Presence Message Channel Adapter

Spring Integration provides an Inbound Presence Message Channel Adapter which supports receiving Presence events from other users in the system who happen to be on your Roster. To do this, the adapter "logs in" as a user on your behalf, registers a RosterListener and forwards received Presence update events as Messages to the channel identified by the channel attribute. The payload of the Message will be a org.jivesoftware.smack.packet.Presence object (see http://www.igniterealtime.org/builds/smack/docs/3.1.0/javadoc/org/jivesoftware/smack/packet/Presence.html).

Configuration support for the XMPP Inbound Presence Message Channel Adapter is provided via the presence-inbound-channel-adapter element.

<int-xmpp:presence-inbound-channel-adapter channel="outChannel" 
		xmpp-connection="testConnection" auto-startup="false"/>

As you can see amongst the usual attributes this adapter also requires a reference to an XMPP Connection. It is also important to mention that this adapter is an event driven adapter and a Lifecycle implementation. It will register a RosterListener when started and will unregister that RosterListener when stopped.

30.4.2 Outbound Presence Message Channel Adapter

Spring Integration also supports sending Presence events to be seen by other users in the network who happen to have you on their Roster. When you send a Message to the Outbound Presence Message Channel Adapter it extracts the payload, which is expected to be of type org.jivesoftware.smack.packet.Presence (see http://www.igniterealtime.org/builds/smack/docs/3.1.0/javadoc/org/jivesoftware/smack/packet/Presence.html) and sends it to the XMPP Connection, thus advertising your presence events to the rest of the network.

Configuration support for the XMPP Outbound Presence Message Channel Adapter is provided via the presence-outbound-channel-adapter element.

<int-xmpp:presence-outbound-channel-adapter id="eventOutboundPresenceChannel" 
	xmpp-connection="testConnection"/>

It can also be a Polling Consumer (if it receives Messages from a Pollable Channel) in which case you would need to register a Poller.

<int-xmpp:presence-outbound-channel-adapter id="pollingOutboundPresenceAdapter" 
		xmpp-connection="testConnection" 
		channel="pollingChannel">
	<int:poller fixed-rate="1000" max-messages-per-poll="1"/>
</int-xmpp:presence-outbound-channel-adapter>

Like its inbound counterpart, it requires a reference to an XMPP Connection.

[Note]Note
If you are relying on the default naming convention for an XMPP Connection bean (described earlier), and you have only one XMPP Connection bean configured in your Application Context, you may omit the xmpp-connection attribute. In that case, the bean with the name xmppConnection will be located and injected into the adapter.

30.5 Appendices

Since Spring Integration XMPP support is based on the Smack 3.1 API (http://www.igniterealtime.org/downloads/index.jsp), it is important to know a few details related to more complex configuration of the XMPP Connection object.

As stated earlier the xmpp-connection namespace support is designed to simplify basic connection configuration and only supports a few common configuration attributes. However, the org.jivesoftware.smack.ConnectionConfiguration object defines about 20 attributes, and there is no real value of adding namespace support for all of them. So, for more complex connection configurations, simply configure an instance of our XmppConnectionFactoryBean as a regular bean, and inject a org.jivesoftware.smack.ConnectionConfiguration as a constructor argument to that FactoryBean. Every property you need, can be specified directly on that ConnectionConfiguration instance (a bean definition with the 'p' namespace would work well). This way SSL, or any other attributes, could be set directly. Here's an example:

<bean id="xmppConnection" class="org.springframework.integration.xmpp.XmppConnectionFactoryBean">
	<constructor-arg>
		<bean class="org.jivesoftware.smack.ConnectionConfiguration">
			<constructor-arg value="myServiceName"/>
			<property name="truststorePath" value="..."/>
			<property name="socketFactory" ref="..."/>
		</bean>
	</constructor-arg>
</bean>
<int:channel id="outboundEventChannel"/>
	
<int-xmpp:outbound-channel-adapter id="outboundEventAdapter" 					     
	channel="outboundEventChannel" 
	xmpp-connection="xmppConnection"/>

Another important aspect of the Smack API is static initializers. For more complex cases (e.g., registering a SASL Mechanism), you may need to execute certain static initializers. One of those static initializers is SASLAuthentication, which allows you to register supported SASL mechanisms. For that level of complexity, we would recommend Spring JavaConfig-style of the XMPP Connection configuration. Then, you can configure the entire component through Java code and execute all other necessary Java code including static initializers at the appropriate time.

@Configuration
public class CustomConnectionConfiguration {
  @Bean
  public XMPPConnection xmppConnection() {
	SASLAuthentication.supportSASLMechanism("EXTERNAL", 0); // static initializer
	                   
	ConnectionConfiguration config = new ConnectionConfiguration("localhost", 5223);
	config.setTrustorePath("path_to_truststore.jks");
	config.setSecurityEnabled(true);
	config.setSocketFactory(SSLSocketFactory.getDefault());
	return new XMPPConnection(config);
  }
}

For more information on the JavaConfig style of Application Context configuration, refer to the following section in the Spring Reference Manual: http://static.springsource.org/spring/docs/3.0.x/spring-framework-reference/html/beans.html#beans-java