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From Claus Ibsen <>
Subject Re: Java8 DSL (CAMEL-7831)
Date Wed, 07 Sep 2016 08:34:16 GMT
Hi Luca

Good to see some experiments with this.

The OUT functions is not needed as end users would only work with the
IN message in the routes. We have deprecated OUT stuff in the Java DSL
in some places.

Just a mind that the goal of Camel 2.18 is to be a gentle Java8
upgrade where the APIs are backwards compatible, so end users can take
any existing Java 7 based Camel 2.17 or older and compile as Java 8
and run on Camel 2.18 as-is.

Therefore we have so far only done Java 8 stuff internally in Camel,
eg inside component implementations and so on.

But your changes seems non invasive and can be a candidate to include.
But we could consider marking that as "experimental" so we can do API
changes for the next release, and when we get more hands down on Camel
3.0 where the APIs can be more Java 8 aggressive.

Also mind that a goal of the DSL is also to let Java and XML be 1:1 so
end users can use the same EIPs in either one, and usually an easy
migration between them, as they are similar. Just be more cautious
when working on Java DSL that you dont end up in a situation with
something that is not possible to do in XML.

Also we should avoid turning the Java DSL into un-readable and
cluttered/complex DSL as the Spring Integration Java DSL:

But this is a great start, and like that its gentle and only about
doing lambda style functions as Camel expressions.

On Tue, Sep 6, 2016 at 5:37 PM, Luca Burgazzoli <> wrote:
> Hello everyone,
> I've started working on CAMEL-7831 to create a Java8 example to use
> Expressions and I've ended up with a simple example - see [1].
> Of course it is only for demonstrative purpose.
> Java8 lambda support to Expressions has been added to
> - ExpressionClause to avoid adding overload method for every method
> accepting an Expressions definition
> - ExpressionBuilder so you can use something like transform(function(e -> ...))
> There are some additional functional interfaces to select the argument
> of the lambda
> - ExchangeFunction
> - MessageFunction
> - BodyFunction
> Any feedback would be really appreciated.
> Regards,
> Luca
> [1]
> ---
> Luca Burgazzoli

Claus Ibsen
----------------- @davsclaus
Camel in Action 2:

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