Configuring the Message Service

To use a Message Service adapter, such as the ActionScript, JMS, or ColdFusion Event Gateway Adapter, you reference the adapter in a destination definition. If you do not explicitly specify an adapter, the destination uses the default adapter as defined in the <adapters> tag. In addition to referencing an adapter, you also set its properties in a destination definition.

The following example shows two adapter definitions: the ActionScriptAdapter and the JMSAdapter. In this example, the ActionScriptAdapter is defined as the default adapter:

<service id="message-service" 
    class="flex.messaging.services.MessageService"> 
    ... 
    <adapters> 
        <adapter-definition  
            id="actionscript" 
            class="flex.messaging.services.messaging. 
            adapters.ActionScriptAdapter" default="true"/> 
        <adapter-definition  
            id="jms" 
            class="flex.messaging.services.messaging.adapters.JMSAdapter"/> 
    </adapters> 
    ... 
    <destination id="chat-topic"> 
        ...     
        <adapter ref="actionscript"/> 
        ... 
    </destination> 
    ... 
</service>

Since ActionScriptAdapter is defined as the default adapter, you can omit the <adapter> tag from the destination definition,

You perform most of the configuration for the Message Service in the destination definition, including specifying the adapter and channels used by the destination, and any network and server properties.

You can create a custom Message Service adapter for situations where you need functionality not provided by the standard adapters. A Message Service adapter class must extend the flex.messaging.services.messaging.adapters.MessagingAdapter class. An adapter calls methods on an instance of a flex.messaging.MessageService object. The MessagingAdapter and MessageService classes are in the flex-messaging-core.jar file. Documentation for these classes is included in the public LiveCycle Data Services Javadoc documentation.

The primary method of any Message Service adapter class is the invoke() method, which is called when a client sends a message to a destination. In the invoke() method, you can include code to send messages to all subscribing clients or to specific clients by evaluating selector statements included with a message.

To send a message to clients, you call the MessageService.pushMessageToClients() method in your adapter's invoke() method. This method takes a message object as its first parameter. Its second parameter is a Boolean value that indicates whether to evaluate message selector statements. You can call the MessageService.sendPushMessageFromPeer() method in your adapter's invoke() method to broadcast messages to peer server nodes in a clustered environment.

package customclasspackage;  
{ 
 
    import flex.messaging.services.messaging.adapters.MessagingAdapter; 
    import flex.messaging.services.MessageService; 
    import flex.messaging.messages.Message; 
    import flex.messaging.Destination; 
 
    public class SimpleCustomAdapter extends MessagingAdapter { 
 
        public Object invoke(Message message) { 
            MessageService msgService = (MessageService)service; 
            msgService.pushMessageToClients(message, true); 
            msgService.sendPushMessageFromPeer(message, true); 
            return null; 
        } 
    } 
}

Optionally, a Message Service adapter can manage its own subscriptions by overriding the ServiceAdapter.handlesSubscriptions() method and return true. You also must override the ServiceAdapter.manage() method, which is passed CommandMessages for subscribe and unsubscribe operations.

The ServiceAdapter.getAdapterState() and ServiceAdapter.setAdapterState() methods are for adapters that maintain an in-memory state that must be replicated across a cluster. When an adapter starts up, it gets a copy of that state from another cluster node when another node is running.

To use an adapter class, specify it in an adapter-definition element in the messaging-config.xml file, as the following example shows:

<adapters> 
... 
    adapter-definition id="cfgateway" class="foo.bar.SampleMessageAdapter"/> 
... 
</adapters>

Optionally, you can implement MBean component management in an adapter. This implementation lets you expose properties to a JMX server that can be used as an administration console. For more information, see Monitoring and managing services.