I'm not sure I understand - addMessageListener takes an object that
implements NotificationMessageListener, and since you right those classes,
they can contain any supplemental info you'd like. If you wanted a
listener that filtered on topics, you could use code that is similar to
that found in the wsn-producer sample. The code below generalizes the
sample code a bit, so that you can use it to filter on any topic:
public class MyTopicListener implements NotificationMessageListener
{
private QName _topicName = null;
public MyTopicListener(QName topicName)
{
_topicName = topicName;
}
public boolean accepts(NotificationMessage msg)
{
QName msgTopicName = msg.getTopic();
return msgTopicName != null &&
msgTopicName.equals(_topicName);
}
public void process(NotificationMessage msg)
{
...
}
}
Then, you can add this listener as follows:
NotificationConsumer wsn =
getResource().getCapability(WsnConstants.CONSUMER_URI);
NotificationMessageListener listener = new MyTopicListener([your topic
name here]);
wsn.addMessageListener(listener);
Of course, even with this, you're right, the consumer capability is still
calling accepts() for each listener to see if they want to respond to the
message. I don't really see how this would be avoided; if you want all of
your listeners to respond to the exact same topic, it would probably be
easier to sub-class SimpleNotificationConsumer and add the following
override:
public class MyTopicNotificationConsumer extends
SimpleNotificationConsumer
{
public void notify(NotificationMessage msg)
{
QName topic = msg.getTopic();
if (topic == null || !topic.equals([your topic name here])
// throw fault
super.notify(msg);
}
}
If you have listeners that are acting on different messages
types/topics/patterns, though, it seems to me that all listeners have to
test it.
Dan
Balan Subramanian/Raleigh/[EMAIL PROTECTED] wrote on 01/05/2007 05:42:37 PM:
> When registering NotificationListeners with the NotificationConsumer,
the
> registering capability only provides a reference to itself but no
> indication of which Topic it wants to subscribe to. It does a separate
> subscribe operation on the topic with the EPR of the resource.
>
> However when a notification message is received, the notification
consumer
> capability has to call accepts() method on each of the registered
> listeners. This seems like a performance issue if you have many
> capabilities and many notifications coming in.
>
> It would be better if the addMessageListener() also took a topic name.
Or
> rather, a new method can be provided like setupSubscription() on the
> notification consumer that will also subscribe to the actual topic
instead
> of the capability having to do this.
>
> if my understanding of the way this works is wrong, please excuse my
> ignorance and provide an explanation of the mechanism. also are there
> other cases in which subscriptions will have to be made by the
> capabilities only?
>
> Balan Subramanian
> Autonomic Computing, IBM, RTP, NC
> 919.543.0197 | [EMAIL PROTECTED]
>
>
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