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https://issues.apache.org/activemq/browse/CAMEL-1638?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=51847#action_51847
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Claus Ibsen commented on CAMEL-1638:
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Willem could you explain a bit more?
I would also like the AggregationStrategy to be a single method to implement as
thats easier for anonym inner classes and also for languages with closure to
support more nicely.
I agree we have a catch-22 situation.
If we leave it like the old way then we loose that first callback, that
- takes end users by the surprise as if they aggregate 10 exchanges they would
expect 10 callbacks
- you lose 1 callback and have to deal with the situation how to remedy this by
eg adding a special "boolean" flag on the exchange that you have
done your own "i missed the first exchange fixup".
With the new way, we get
- all 10 callbacks is executed and end users is not surprised
- however the first callback have {{null}} for oldExchange
BTW: As a side note I am speculating how to allow a POJO to be
AggregatorStrategy so we dont have to use Camel API at all. But I will create a
new ticket for that as well.
> AggregatorStrategy - should also be invoked for the first exchange
> ------------------------------------------------------------------
>
> Key: CAMEL-1638
> URL: https://issues.apache.org/activemq/browse/CAMEL-1638
> Project: Apache Camel
> Issue Type: Improvement
> Components: camel-core
> Affects Versions: 2.0-M1, 1.6.1
> Reporter: Claus Ibsen
> Assignee: Claus Ibsen
> Fix For: 2.0.0
>
>
> Using aggregator, splitterl, multicast etc. that supports
> {{AggregatorStrategy}} all have the flaw that they skip invoking this
> interface callback for the very first exchange.
> This hazzles the end users implementing this interface if they are to be able
> to traverse all the exchanges, to eg summing a total amount or the likes.
> And its also a bit confusing as well why the first one is skipped.
> And if you aggregator out of order then you dont know which one was the first
> exchange.
> So we should invoke this callback always. And the first time the
> {{oldExchange}} parameter is null.
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