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: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-2.0.xsd"

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.

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

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.

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

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

<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>

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