Adobe® Flex® 4 Language Reference
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mx.messaging 
Channel 
Packagemx.messaging
Classpublic class Channel
InheritanceChannel Inheritance EventDispatcher Inheritance Object
Implements IMXMLObject
Subclasses PollingChannel

Language Version: ActionScript 3.0
Product Versions: BlazeDS 4, LiveCycle Data Services 3
Runtime Versions: Flash Player 9, AIR 1.1

The Channel class is the base message channel class that all channels in the messaging system must extend.

Channels are specific protocol-based conduits for messages sent between MessageAgents and remote destinations. Preconfigured channels are obtained within the framework using the ServerConfig.getChannel() method. You can create a Channel directly using the new operator and add it to a ChannelSet directly.

Channels represent a physical connection to a remote endpoint. Channels are shared across destinations by default. This means that a client targetting different destinations may use the same Channel to communicate with these destinations.

Note: This class is for advanced use only. Use this class for creating custom channels like the existing RTMPChannel, AMFChannel, and HTTPChannel.



Public Properties
 PropertyDefined By
  authenticated : Boolean
[read-only] Indicates if this channel is authenticated.
Channel
  channelSets : Array
[read-only] Provides access to the ChannelSets connected to the Channel.
Channel
  connected : Boolean
[read-only] Indicates whether this channel has established a connection to the remote destination.
Channel
  connectTimeout : int
Provides access to the connect timeout in seconds for the channel.
Channel
 Inheritedconstructor : Object
A reference to the class object or constructor function for a given object instance.
Object
  endpoint : String
[read-only] Provides access to the endpoint for this channel.
Channel
  failoverURIs : Array
Provides access to the set of endpoint URIs that this channel can attempt to failover to if the endpoint is clustered.
Channel
  id : String
Provides access to the id of this channel.
Channel
  protocol : String
[read-only] Provides access to the protocol that the channel uses.
Channel
 Inheritedprototype : Object
[static] A reference to the prototype object of a class or function object.
Object
  reconnecting : Boolean
[read-only] Indicates whether this channel is in the process of reconnecting to an alternate endpoint.
Channel
  recordMessageSizes : Boolean
[read-only] Channel property determines the level of performance information injection - whether we inject message sizes or not.
Channel
  recordMessageTimes : Boolean
[read-only] Channel property determines the level of performance information injection - whether we inject timestamps or not.
Channel
  requestTimeout : int
Provides access to the default request timeout in seconds for the channel.
Channel
  uri : String
Provides access to the URI used to create the whole endpoint URI for this channel.
Channel
Protected Properties
 PropertyDefined By
  shouldBeConnected : Boolean
[read-only] Indicates whether this channel should be connected to its endpoint.
Channel
Public Methods
 MethodDefined By
  
Channel(id:String = null, uri:String = null)
Constructs an instance of a generic Channel that connects to the specified endpoint URI.
Channel
 Inherited
addEventListener(type:String, listener:Function, useCapture:Boolean = false, priority:int = 0, useWeakReference:Boolean = false):void
Registers an event listener object with an EventDispatcher object so that the listener receives notification of an event.
EventDispatcher
  
Subclasses should override this method to apply any settings that may be necessary for an individual channel.
Channel
  
connect(channelSet:ChannelSet):void
Connects the ChannelSet to the Channel.
Channel
  
Disconnects the ChannelSet from the Channel.
Channel
 Inherited
Dispatches an event into the event flow.
EventDispatcher
 Inherited
Checks whether the EventDispatcher object has any listeners registered for a specific type of event.
EventDispatcher
 Inherited
Indicates whether an object has a specified property defined.
Object
 Inherited
Indicates whether an instance of the Object class is in the prototype chain of the object specified as the parameter.
Object
  
Sends a CommandMessage to the server to logout if the Channel is connected.
Channel
 Inherited
Indicates whether the specified property exists and is enumerable.
Object
 Inherited
removeEventListener(type:String, listener:Function, useCapture:Boolean = false):void
Removes a listener from the EventDispatcher object.
EventDispatcher
  
send(agent:MessageAgent, message:IMessage):void
Sends the specified message to its target destination.
Channel
  
setCredentials(credentials:String, agent:MessageAgent = null, charset:String = null):void
Sets the credentials to the specified value.
Channel
 Inherited
Sets the availability of a dynamic property for loop operations.
Object
 Inherited
Returns the string representation of this object, formatted according to locale-specific conventions.
Object
 Inherited
Returns the string representation of the specified object.
Object
 Inherited
Returns the primitive value of the specified object.
Object
 Inherited
Checks whether an event listener is registered with this EventDispatcher object or any of its ancestors for the specified event type.
EventDispatcher
Protected Methods
 MethodDefined By
  
Applies the client load balancing urls if they exists.
Channel
  
Processes a failed internal connect and dispatches the FAULT event for the channel.
Channel
  
Processes a successful internal connect and dispatches the CONNECT event for the Channel.
Channel
  
Handles a connect timeout by dispatching a ChannelFaultEvent.
Channel
  
Processes a failed internal disconnect and dispatches the FAULT event for the channel.
Channel
  
disconnectSuccess(rejected:Boolean = false):void
Processes a successful internal disconnect and dispatches the DISCONNECT event for the Channel.
Channel
  
Handles a change to the guard condition for managing initial Channel connect for the application.
Channel
  
Returns the appropriate MessageResponder for the Channel's send() method.
Channel
  
Connects the Channel to its endpoint.
Channel
  
internalDisconnect(rejected:Boolean = false):void
Disconnects the Channel from its endpoint.
Channel
  
Sends the Message out over the Channel and routes the response to the responder.
Channel
Events
 Event Summary Defined By
 Inherited[broadcast event] Dispatched when the Flash Player or AIR application gains operating system focus and becomes active.EventDispatcher
  Dispatched after the channel has connected to its endpoint.Channel
  Dispatched after the channel has disconnected from its endpoint.Channel
  Dispatched after the channel has faulted.Channel
 Inherited[broadcast event] Dispatched when the Flash Player or AIR application operating loses system focus and is becoming inactive.EventDispatcher
  Dispatched when a channel receives a message from its endpoint.Channel
  Dispatched when a property of the channel changes.Channel
Property Detail

authenticated

property
authenticated:Boolean  [read-only]

Indicates if this channel is authenticated.

This property can be used as the source for data binding. When this property is modified, it dispatches the propertyChange event.



Implementation
    public function get authenticated():Boolean

channelSets

property 
channelSets:Array  [read-only]

Language Version: ActionScript 3.0
Product Versions: BlazeDS 4, LiveCycle Data Services 3
Runtime Versions: Flash Player 9, AIR 1.1

Provides access to the ChannelSets connected to the Channel.



Implementation
    public function get channelSets():Array

connected

property 
connected:Boolean  [read-only]

Language Version: ActionScript 3.0
Product Versions: BlazeDS 4, LiveCycle Data Services 3
Runtime Versions: Flash Player 9, AIR 1.1

Indicates whether this channel has established a connection to the remote destination.

This property can be used as the source for data binding. When this property is modified, it dispatches the propertyChange event.



Implementation
    public function get connected():Boolean

connectTimeout

property 
connectTimeout:int

Language Version: ActionScript 3.0
Product Versions: BlazeDS 4, LiveCycle Data Services 3
Runtime Versions: Flash Player 9, AIR 1.1

Provides access to the connect timeout in seconds for the channel. A value of 0 or below indicates that a connect attempt will never be timed out on the client. For channels that are configured to failover, this value is the total time to wait for a connection to be established. It is not reset for each failover URI that the channel may attempt to connect to.



Implementation
    public function get connectTimeout():int
    public function set connectTimeout(value:int):void

endpoint

property 
endpoint:String  [read-only]

Provides access to the endpoint for this channel. This value is calculated based on the value of the uri property.



Implementation
    public function get endpoint():String

failoverURIs

property 
failoverURIs:Array

Provides access to the set of endpoint URIs that this channel can attempt to failover to if the endpoint is clustered.

This property is automatically populated when clustering is enabled. If you don't use clustering, you can set your own values.



Implementation
    public function get failoverURIs():Array
    public function set failoverURIs(value:Array):void

id

property 
id:String

Provides access to the id of this channel.



Implementation
    public function get id():String
    public function set id(value:String):void

protocol

property 
protocol:String  [read-only]

Provides access to the protocol that the channel uses.

Note: Subclasses of Channel must override this method and return a string that represents their supported protocol. Examples of supported protocol strings are "rtmp", "http" or "https".



Implementation
    public function get protocol():String

reconnecting

property 
reconnecting:Boolean  [read-only]

Indicates whether this channel is in the process of reconnecting to an alternate endpoint.

This property can be used as the source for data binding. When this property is modified, it dispatches the propertyChange event.



Implementation
    public function get reconnecting():Boolean

recordMessageSizes

property 
recordMessageSizes:Boolean  [read-only]

Language Version: ActionScript 3.0
Product Versions: BlazeDS 4, LiveCycle Data Services 3
Runtime Versions: Flash Player 9, AIR 1.1

Channel property determines the level of performance information injection - whether we inject message sizes or not.



Implementation
    public function get recordMessageSizes():Boolean

recordMessageTimes

property 
recordMessageTimes:Boolean  [read-only]

Language Version: ActionScript 3.0
Product Versions: BlazeDS 4, LiveCycle Data Services 3
Runtime Versions: Flash Player 9, AIR 1.1

Channel property determines the level of performance information injection - whether we inject timestamps or not.



Implementation
    public function get recordMessageTimes():Boolean

requestTimeout

property 
requestTimeout:int

Provides access to the default request timeout in seconds for the channel. A value of 0 or below indicates that outbound requests will never be timed out on the client.

Request timeouts are most useful for RPC style messaging that requires a response from the remote destination.



Implementation
    public function get requestTimeout():int
    public function set requestTimeout(value:int):void

shouldBeConnected

property 
shouldBeConnected:Boolean  [read-only]

Indicates whether this channel should be connected to its endpoint. This flag is used to control when fail over should be attempted and when disconnect notification is sent to the remote endpoint upon disconnect or fault.



Implementation
    protected function get shouldBeConnected():Boolean

uri

property 
uri:String

Provides access to the URI used to create the whole endpoint URI for this channel. The URI can be a partial path, in which case the full endpoint URI is computed as necessary.



Implementation
    public function get uri():String
    public function set uri(value:String):void
Constructor Detail

Channel

()Constructor
public function Channel(id:String = null, uri:String = null)

Language Version: ActionScript 3.0
Product Versions: BlazeDS 4, LiveCycle Data Services 3
Runtime Versions: Flash Player 9, AIR 1.1

Constructs an instance of a generic Channel that connects to the specified endpoint URI. Note: The Channel type should not be constructed directly. Instead create instances of protocol specific subclasses such as RTMPChannel or AMFChannel.

Parameters
id:String (default = null) — The id of this channel.
 
uri:String (default = null) — The endpoint URI for this channel.
Method Detail

applyClientLoadBalancingSettings

()method
protected function applyClientLoadBalancingSettings(props:XML):void

Applies the client load balancing urls if they exists. It randomly picks a url from the set of client load balancing urls and sets it as the channel's main url; then it assigns the rest of the urls as the failoverURIs of the channel.

Parameters

props:XML — The properties section of the XML fragment of the services-config.xml file for this channel.

applySettings

()method 
public function applySettings(settings:XML):void

Subclasses should override this method to apply any settings that may be necessary for an individual channel. Make sure to call super.applySettings() to apply common settings for the channel. This method is used primarily in Channel subclasses.

Parameters

settings:XML — XML fragment of the services-config.xml file for this channel.

connect

()method 
public final function connect(channelSet:ChannelSet):void

Connects the ChannelSet to the Channel. If the Channel has not yet connected to its endpoint, it attempts to do so. Channel subclasses must override the internalConnect() method, and call the connectSuccess() method once the underlying connection is established.

Parameters

channelSet:ChannelSet — The ChannelSet to connect to the Channel.

connectFailed

()method 
protected function connectFailed(event:ChannelFaultEvent):void

Processes a failed internal connect and dispatches the FAULT event for the channel. If the Channel has failoverURI values, it will attempt to reconnect automatically by trying these URI values in order until a connection is established or the available values are exhausted.

Parameters

event:ChannelFaultEvent — The ChannelFaultEvent for the failed connect.

connectSuccess

()method 
protected function connectSuccess():void

Processes a successful internal connect and dispatches the CONNECT event for the Channel.

connectTimeoutHandler

()method 
protected function connectTimeoutHandler(event:flash.events:TimerEvent):void

Handles a connect timeout by dispatching a ChannelFaultEvent. Subtypes may overide this to shutdown the current connect attempt but must call super.connectTimeoutHandler(event).

Parameters

event:flash.events:TimerEvent — The timer event indicating that the connect timeout has been reached.

disconnect

()method 
public final function disconnect(channelSet:ChannelSet):void

Disconnects the ChannelSet from the Channel. If the Channel is connected to its endpoint and it has no more connected ChannelSets it will internally disconnect.

Channel subclasses need to override the internalDisconnect() method, and call the disconnectSuccess() method when the underlying connection has been terminated.

Parameters

channelSet:ChannelSet — The ChannelSet to disconnect from the Channel.

disconnectFailed

()method 
protected function disconnectFailed(event:ChannelFaultEvent):void

Processes a failed internal disconnect and dispatches the FAULT event for the channel.

Parameters

event:ChannelFaultEvent — The ChannelFaultEvent for the failed disconnect.

disconnectSuccess

()method 
protected function disconnectSuccess(rejected:Boolean = false):void

Processes a successful internal disconnect and dispatches the DISCONNECT event for the Channel. If the disconnect is due to a network failure and the Channel has failoverURI values, it will attempt to reconnect automatically by trying these URI values in order until a connection is established or the available values are exhausted.

Parameters

rejected:Boolean (default = false) — True if the disconnect should skip any failover processing that would otherwise be attempted; false if failover processing should be allowed to run.

flexClientWaitHandler

()method 
protected function flexClientWaitHandler(event:PropertyChangeEvent):void

Handles a change to the guard condition for managing initial Channel connect for the application. When this is invoked it means that this Channel is waiting to attempt to connect.

Parameters

event:PropertyChangeEvent — The PropertyChangeEvent dispatched by the FlexClient singleton.

getMessageResponder

()method 
protected function getMessageResponder(agent:MessageAgent, message:IMessage):MessageResponder

Returns the appropriate MessageResponder for the Channel's send() method. Must be overridden.

Parameters

agent:MessageAgent — The MessageAgent sending the message.
 
message:IMessage — The Message to send.

Returns
MessageResponder — The MessageResponder to handle the result or fault.

Throws
IllegalOperationError — If the Channel subclass does not override this method.

internalConnect

()method 
protected function internalConnect():void

Connects the Channel to its endpoint. Must be overridden.

internalDisconnect

()method 
protected function internalDisconnect(rejected:Boolean = false):void

Disconnects the Channel from its endpoint. Must be overridden.

Parameters

rejected:Boolean (default = false) — True if the disconnect was due to a connection rejection or timeout and reconnection should not be attempted automatically; otherwise false.

internalSend

()method 
protected function internalSend(messageResponder:MessageResponder):void

Sends the Message out over the Channel and routes the response to the responder. Must be overridden.

Parameters

messageResponder:MessageResponder — The MessageResponder to handle the response.

logout

()method 
public function logout(agent:MessageAgent):void

Sends a CommandMessage to the server to logout if the Channel is connected. Current credentials are cleared.

Parameters

agent:MessageAgent — The MessageAgent to logout.

send

()method 
public function send(agent:MessageAgent, message:IMessage):void

Sends the specified message to its target destination. Subclasses must override the internalSend() method to perform the actual send.

Parameters

agent:MessageAgent — The MessageAgent that is sending the message.
 
message:IMessage — The Message to send.


Throws
InvalidDestinationError — If neither the MessageAgent nor the message specify a destination.

setCredentials

()method 
public function setCredentials(credentials:String, agent:MessageAgent = null, charset:String = null):void

Sets the credentials to the specified value. If the credentials are non-null and the Channel is connected, this method also sends a CommandMessage to the server to login using the credentials.

Parameters

credentials:String — The credentials string.
 
agent:MessageAgent (default = null) — The MessageAgent to login, that will handle the login result.
 
charset:String (default = null) — The character set encoding used while encoding the credentials. The default is null, which implies the legacy charset of ISO-Latin-1.


Throws
IllegalOperationError — in two situations; if credentials have already been set and an authentication is in progress with the remote detination, or if authenticated and the credentials specified don't match the currently authenticated credentials.
Event Detail

channelConnect

Event
Event Object Type: mx.messaging.events.ChannelEvent
property ChannelEvent.type = mx.messaging.events.ChannelEvent.CONNECT

Dispatched after the channel has connected to its endpoint.

Channel and its subclasses issue a Channel.Connect.Failed code whenever there is an issue in a channel's connect attempts to a remote destination. An AMFChannel object issues Channel.Call.Failed code when the channel is already connected but it gets a Call.Failed code from its underlying NetConnection.

The CONNECT event type; indicates that the Channel connected to its endpoint.

The value of this constant is "channelConnect".

The properties of the event object have the following values:

PropertyValue
bubblesfalse
cancelablefalse
channelThe channel that generated this event.
currentTargetThe Object that defines the event listener that handles the event. For example, if you use myButton.addEventListener() to register an event listener, myButton is the value of the currentTarget.
targetThe Object that dispatched the event; it is not always the Object listening for the event. Use the currentTarget property to always access the Object listening for the event.
reconnecting Indicates whether the channel that generated this event is reconnecting.
rejected Indicates whether the channel that generated this event was rejected. This would be true in the event that the channel has been disconnected due to inactivity and should not attempt to failover or connect on an alternate channel.

channelDisconnect

Event  
Event Object Type: mx.messaging.events.ChannelEvent
property ChannelEvent.type = mx.messaging.events.ChannelEvent.DISCONNECT

Language Version: ActionScript 3.0
Product Versions: BlazeDS 4, LiveCycle Data Services 3
Runtime Versions: Flash Player 9, AIR 1.1

Dispatched after the channel has disconnected from its endpoint.

The DISCONNECT event type; indicates that the Channel disconnected from its endpoint.

The value of this constant is "channelDisconnect".

The properties of the event object have the following values:

PropertyValue
bubblesfalse
cancelablefalse
channelThe channel that generated this event.
currentTargetThe Object that defines the event listener that handles the event. For example, if you use myButton.addEventListener() to register an event listener, myButton is the value of the currentTarget.
targetThe Object that dispatched the event; it is not always the Object listening for the event. Use the currentTarget property to always access the Object listening for the event.
reconnecting Indicates whether the channel that generated this event is reconnecting.
rejected Indicates whether the channel that generated this event was rejected. This would be true in the event that the channel has been disconnected due to inactivity and should not attempt to failover or connect on an alternate channel.

channelFault

Event  
Event Object Type: mx.messaging.events.ChannelFaultEvent
property ChannelFaultEvent.type = mx.messaging.events.ChannelFaultEvent.FAULT

Language Version: ActionScript 3.0
Product Versions: BlazeDS 4, LiveCycle Data Services 3
Runtime Versions: Flash Player 9, AIR 1.1

Dispatched after the channel has faulted.

The FAULT event type; indicates that the Channel faulted.

The value of this constant is "channelFault".

The properties of the event object have the following values:

PropertyValue
bubblesfalse
cancelablefalse
channelThe Channel that generated this event.
currentTargetThe Object that defines the event listener that handles the event. For example, if you use myButton.addEventListener() to register an event listener, myButton is the value of the currentTarget.
faultCodeProvides destination-specific details of the failure.
faultDetailProvides access to the destination-specific reason for the failure.
faultStringProvides access to the underlying reason for the failure if the channel did not raise the failure itself.
reconnecting Indicates whether the channel that generated this event is reconnecting.
rootCause Provides access to the underlying reason for the failure if the channel did not raise the failure itself.
targetThe Object that dispatched the event; it is not always the Object listening for the event. Use the currentTarget property to always access the Object listening for the event.

message

Event  
Event Object Type: mx.messaging.events.MessageEvent
property MessageEvent.type = mx.messaging.events.MessageEvent.MESSAGE

Language Version: ActionScript 3.0
Product Versions: BlazeDS 4, LiveCycle Data Services 3
Runtime Versions: Flash Player 9, AIR 1.1

Dispatched when a channel receives a message from its endpoint.

The MESSAGE event type; dispatched upon receipt of a message.

The value of this constant is "message".

The properties of the event object have the following values:

PropertyValue
bubblesfalse
cancelablefalse
currentTargetThe Object that defines the event listener that handles the event. For example, if you use myButton.addEventListener() to register an event listener, myButton is the value of the currentTarget.
messageThe message associated with this event.
targetThe Object that dispatched the event; it is not always the Object listening for the event. Use the currentTarget property to always access the Object listening for the event.

propertyChange

Event  
Event Object Type: mx.events.PropertyChangeEvent
property PropertyChangeEvent.type = mx.events.PropertyChangeEvent.PROPERTY_CHANGE

Language Version: ActionScript 3.0
Product Versions: BlazeDS 4, LiveCycle Data Services 3
Runtime Versions: Flash Player 9, AIR 1.1

Dispatched when a property of the channel changes.

The PropertyChangeEvent.PROPERTY_CHANGE constant defines the value of the type property of the event object for a PropertyChange event.

The properties of the event object have the following values:

PropertyValue
bubblesDetermined by the constructor; defaults to false.
cancelableDetermined by the constructor; defaults to false.
kindThe kind of change; PropertyChangeEventKind.UPDATE or PropertyChangeEventKind.DELETE.
oldValueThe original property value.
newValueThe new property value, if any.
propertyThe property that changed.
sourceThe object that contains the property that changed.
currentTargetThe Object that defines the event listener that handles the event. For example, if you use myButton.addEventListener() to register an event listener, myButton is the value of the currentTarget.
targetThe Object that dispatched the event; it is not always the Object listening for the event. Use the currentTarget property to always access the Object listening for the event.