org.mortbay.cometd
Class BayeuxService

java.lang.Object
  extended by org.mortbay.cometd.BayeuxService
Direct Known Subclasses:
BayeuxStartupListener.EchoRPC

public abstract class BayeuxService
extends Object

Abstract Bayeux Service class. This is a base class to assist with the creation of server side clients that provide services to remote Bayeux clients. The class provides a Bayeux Client and Listener together with convenience methods to map subscriptions to methods on the derived class and to send responses to those methods.

Author:
gregw

Constructor Summary
BayeuxService(Bayeux bayeux, String name)
          Instantiate the service.
 
Method Summary
protected  void exception(Client fromClient, Client toClient, Map<String,Object> msg, Throwable th)
          Handle Exception.
 Bayeux getBayeux()
           
 Client getClient()
           
protected  void send(Client toClient, String onChannel, Object data, String id)
          Send data to a individual client.
protected  void subscribe(String channel, String methodName)
          Subscribe to a channel.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

BayeuxService

public BayeuxService(Bayeux bayeux,
                     String name)
Instantiate the service. Typically the derived constructor will call to map subscriptions to methods.

Parameters:
bayeux - The bayeux instance.
name - The name of the service (used as client ID prefix).
Method Detail

getBayeux

public Bayeux getBayeux()

getClient

public Client getClient()

subscribe

protected void subscribe(String channel,
                         String methodName)
Subscribe to a channel. Subscribe to channel and map a method to handle received messages. The method must have a unique name and take 2 or 3 arguments: myMethod(Client fromClient,Object data,String id) with the id parameter being optional. The data parameter can be typed if the type of the data object published by the client is known (typically Map)

Typically a service will subscribe to a channel in the "/service/**" space which is not a broadcast channel. Messages published to these channels are only delivered to server side clients like this service.

Any object returned by a mapped subscription method is delivered to the calling client and not broadcast. If the method returns void or null, then no response is sent. A mapped subscription method may also call send(Client, String, Object, String) to deliver a response message(s) to different clients and/or channels. It may also publish methods via the normal Bayeux API.

Parameters:
channel - The channel to subscribe to
methodName - The name of the method on this object to call when messages are recieved.

send

protected void send(Client toClient,
                    String onChannel,
                    Object data,
                    String id)
Send data to a individual client. The data passed is sent to the client as the "data" member of a message with the given channel and id. The message is not published on the channel and is thus not broadcast to all channel subscribers. However to the target client, the message appears as if it was broadcast.

Typcially this method is only required if a service method sends response(s) to channels other than the subscribed channel. If the response is to be sent to the subscribed channel, then the data can simply be returned from the subscription method.

Parameters:
toClient - The target client
onChannel - The channel the message is for
data - The data of the message
id - The id of the message (or null for a random id).

exception

protected void exception(Client fromClient,
                         Client toClient,
                         Map<String,Object> msg,
                         Throwable th)
Handle Exception. This method is called when a mapped subscription method throws and exception while handling a message.

Parameters:
fromClient -
toClient -
msg -
th -


Copyright © 2008 Mort Bay Consulting. All Rights Reserved.