PollableSource

[markn]

I want to have a class implementing this interface but it isn't recognised using the source-adapter ref attribute. It seems I can wire a method up such as T getData().

Under the covers, the ChannelAdapterParser creates a MethodInvokingSource. I'd like it to use my PollableSource instead.

Fyi - I am implementing functionality to retrieve events from another database.

How should I implement this logic?

[iwein]

I'm a bit confused. Can you provide some code samples to explain what you're trying to do exactly?

It would also help if you gave some more detail on the use case.

[markn]

Ok, so I have this working:

<source-adapter channel="events" method="hoover" ref="task-hoover" period="3000"/>
<beans:bean id="task-hoover" class="stockroom.TaskHoover" />

TaskHoover has a method signature and implementation:

	
public Event hoover()
{
	return new Event("Hello " + count++);
}

With this the hoover() method is called every 3 seconds. This is good, but I need to return a collection of Event objects. (Use case is I am pulling event data from an external data source, then constructing event objects which go to the events channel which is pub-sub).

What I want to do is implement the PollableSource interface in this class and be able to configure it using the source-adapter without passing the method ref.

What I was saying before is that the ChannelAdapterParser creates a MethodInvokingSource which implements PollableSource when parsing a source-adapter. So how do I make use of a custom implementation of PollableSource. Is such an approach desirable?

[Mark Fisher]

This makes perfect sense to me, and it is consistent with other areas of Spring Integration (and Spring in general) where 'ref' alone is sufficient if the referenced bean implements a particular strategy interface. When the referenced bean does not implement the interface, then 'method' can be added to create a "MethodInvoking" adapter that does implement the interface. Can you create a Jira issue for this? We are planning some changes to the source-adapter approach in M4, and I would like to include the feature you've described here.

Thanks,
Mark

[markn]

http://jira.springframework.org/browse/INT-157

[Mark Fisher]

Progress is starting on this issue. Note that it's part of a larger refactoring effort aimed at providing a more intuitive separation of "source" and "adapter". For example, any implementation of PollableSource should be capable of being scheduled and activated as a SourceAdapter. On the other hand, there are also cases where the source may only be required "on-demand". In that sense, a source is much like a MessageChannel. It is perfectly acceptable to call channel.receive() programmatically, but with the MessageBus, it is also possible to subscribe to the channel via a scheduled MessageDispatcher.

That's the general idea, and as always feedback is much appreciated.

Thanks,
Mark

[Mark Fisher]

This should be possible now with the following configuration:

<source-endpoint source="mySource" channel="myChannel">
    <schedule period="60000"/>
</source-endpoint>

<beans:bean id="mySource" class="example.MyPollableSource"/>

Note that this will work if you check out the SVN head (or a nightly snapshot >= ci.111): http://static.springframework.org/do...hp?project=INT

-Mark