Agile Enterprise Application Development with Flex

Sending the Client’s Heartbeats

To send the client’s heartbeats, you need a class to represent the heartbeat and a producer to perform the sending.

The heartbeat message object will leverage available Flex/Java serialization—therefore, you’ll need to come up with a pair of almost identical classes: one in Java and the other one in ActionScript. The corresponding classes are presented in Examples 5-1 and 5-2. Notice the array received, which will eventually carry delivery confirmations of the latest received messages.

Example 5-1. ClientHeartbeatMessage.as

package com.farata.messaging.messages {
import mx.messaging.messages.AbstractMessage;

[RemoteClass(alias="com.farata.messaging.messages.ClientHeartbeatMessage")]
public  class ClientHeartbeatMessage
                   extends mx.messaging.messages.AbstractMessage {

   public var received:Array; //Messages arrived since last heartbeat

    public function ClientHeartbeatMessage() {
      super();
         //TODO - populate array "received" - later...
   }
 }
}

Example 5-2. ClientHeartbeatMessage.java

package com.farata.messaging.messages;
import flex.messaging.messages.AbstractMessage;

public class ClientHeartbeatMessage extends AbstractMessage {

  public String[] received; // Array of <ClientID>|<MsgNumber> strings
}

To periodically send the heartbeat message (Example 5-1) up to the server you need a Flex Producer class powered with a Timer. Example 5-3 illustrates the custom ClientHeartbeatProducer class with the startHeartbeat() and stopHeartbeat() methods. By default, the heartbeat ...