camel-users mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Hadrian Zbarcea <>
Subject Re: echo() processor
Date Thu, 21 Aug 2008 16:31:45 GMT
The DSL is big as it is.  We add to it integration patterns, but my  
personal preference would be to not add things like echo().  I would  
more in favor of having it a (static) method that returns a processor,  
so one would use it like:


My $0.02,

On Aug 21, 2008, at 10:49 AM, Fintan Bolton wrote:

> Hi Hadrian,
> Sorry, my terminology in the post was confusing. There are no  
> requests and
> replies in Camel, of course. By 'request', I was referring to the In  
> message
> that is destined to become the request to the "cxf:bean:MyService"  
> service
> and by 'reply', I was referring to the message returned from the
> "cxf:bean:MyService" endpoint (which propagates as an In message in  
> the
> second half of the route).
> Here is a simpler (working) example, which might be clearer:
>        from("jetty:http://localhost:8080/foo")
>          .setBody(constant("&gt;b&lt;Hello World\</b\>"));
> If you point your browser at the address, http://localhost:8080/foo,  
> you'll
> get a blank page (i.e. no reply), because this route does not  
> generate an
> Out message. Now modify the route to the following:
>        from("jetty:http://localhost:8080/foo")
>          .setBody(constant("\<b\>Hello World\</b\>"))
>          .transform(body());
> If you now point your browser at http://localhost:8080/foo, you'll  
> see the
> string "Hello World", because the In message has been copied to the  
> Out
> message by transform(body()) (which is semantically equivalent to the
> proposed echo()).
> Now this example is rather contrived, because you could have made it  
> work in
> the first place by using setOutBody() instead of setBody(). But in  
> many
> cases, it could happen that the last processor in your route happens  
> to
> produce an In message instead of an Out message. In this case, you'd  
> have to
> finish your route with transform(body()) (or, equivalently, echo()),  
> to copy
> the In message to the Out message.
> My hypothesis is that this _might_ be a common pattern for routes that
> process InOut exchanges, in which case an echo() processor would be  
> a handy
> convenience. On the other hand, maybe my sample route is actually an  
> exotic
> rarity :-). I noticed that the Camel doc has more examples of routes  
> that
> process InOnly exchanges than InOut exchanges.
> -
> Fintan
> Hadrian Zbarcea wrote:
>> Hi Fintan,
>> I don't see how this would help.  There is no request and reply per
>> se, there is just an exchange that has messages.  During processing
>> the in and out messages will change many times and whatever will be
>> the out message at the end of the pipeline will be sent as a reply to
>> the caller.  As such, with or without echo(), same thing will happen.
>> I hope I didn't misunderstand your point.
>> Hadrian
>> On Aug 21, 2008, at 6:48 AM, Fintan Bolton wrote:
>>> Hi,
>>> Is there a case for adding an echo() processor to the fluent DSL,
>>> where the
>>> echo() processor simply copies the In message to the Out message?
>>> This could
>>> be useful for capping off routes that process InOut exchanges. For
>>> example:
>>> from("jetty:http://FooHost/Bar")
>>> .process(...).process(...)
>>> .to("cxf:bean:MyService")
>>> .process(...).process(...)
>>> .echo();
>>> Where this example wraps a CXF Web service endpoint. The first
>>> couple of
>>> processors, process(..), do work on the Web service _request_, and  
>>> the
>>> processors that come after to(...) do work on the Web service
>>> _reply_. At
>>> the end of the route, you need to reflect the the reply back to the
>>> endpoint. An echo() processor would be handy for this purpose.
>>> I realize that this is not tremendously critical, because you could
>>> already
>>> use 'transform(body())' to achieve the same effect. But using an
>>> echo()
>>> processor is possibly more elegant.
>>> -
>>> Fintan
>>> -- 
>>> View this message in context:
>>> Sent from the Camel - Users mailing list archive at
> :-):-)
> -- 
> View this message in context:
> Sent from the Camel - Users mailing list archive at

View raw message