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From Claus Ibsen <claus.ib...@gmail.com>
Subject Re: Observer Pattern using Camel
Date Thu, 16 Jun 2011 03:39:54 GMT
Try extending some base class for your anonymous listener interface,
so there is a class.

public class MyListener implements Listener {
   ..
}

The class may even be abstract.

And use new MyListener to instantiate the class. This may work then.



On Wed, Jun 15, 2011 at 6:01 PM, krishy <calvinkrishy@gmail.com> wrote:
> I am working on a abstraction library that would allow a bunch of our
> web-apps to include that library and
> publish and subscribe to JMS destinations (and do other magical things).
> Publication works fine (at least on
> the POC I have!) but I am having trouble wrapping my head around
> subscriptions.
>
> The following method should allow clients to dynamically register for events
> from a JMS endpoint. My
> current implementation looks like this:
>
> <code>
> public void addListener(Event event, Listener listener){
>    try {
>        camelContext.addRoutes(new RouteBuilder() {
>            @Override
>            public void configure() throws Exception {
>                from(event.from()).bean(listener);
>            }
>        });
>    } catch (Exception exception) {
>        exception.printStackTrace();
>    }
>
> }
> </code>
>
> event.from() above would identify the endpoint from which the message would
> be consumed
> ("activemq:topic:market.stocks.update.ibm") and listener would be an
> implementation of a Listener
> interface.
>
> I had envisaged a typical invocation as:
>
> <code>
> notifications.addListener(updateEvent, new Listener(){
>    void listen(){
>        System.out.println("Hey! Something got updated");
>    }
> });
> </code>
>
> In theory, I like this approach since this frees me from having to worry
> about who is subscribed to which
> queue, on what selectors etc, and I can have Camel automagically route these
> messages to the interested
> listeners.
>
> Except, of course, none of the above works since the camel route seems to
> expect a concrete bean as the
> recipient and hence camel context fails to start-up. The actual error:
>
> Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException:
> No matching bean of type
> [com.example.Listener] found for dependency: expected at least 1 bean which
> qualifies as autowire
> candidate for this dependency. Dependency annotations: {}
>
> Am I shoe-horning Camel into something it was not supposed to do? Though,
> the Event Message EIP seems
> to suggest this should work (except that the examples don't seem to address
> the dynamic nature of the listeners)
>
> http://camel.apache.org/event-message.html
>
> Being a Camel newbie, there is another aspect of this which I don't
> understand. This route even though
> part of a method seems to get started when the Camel context starts up. How
> does the route get added
> when the method that is supposed to add it to the context has not been
> invoked?
>
> Thanks for your help and pointers.
>
> --
> View this message in context: http://camel.465427.n5.nabble.com/Observer-Pattern-using-Camel-tp4491726p4491726.html
> Sent from the Camel - Users mailing list archive at Nabble.com.
>



-- 
Claus Ibsen
-----------------
FuseSource
Email: cibsen@fusesource.com
Web: http://fusesource.com
Twitter: davsclaus, fusenews
Blog: http://davsclaus.blogspot.com/
Author of Camel in Action: http://www.manning.com/ibsen/

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