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From Tarjei Huse <tar...@scanmine.com>
Subject Re: Camel Exchange Patters
Date Sat, 25 Sep 2010 08:01:04 GMT
 On 09/24/2010 03:16 PM, Hadrian Zbarcea wrote:
> That's a bit extreme, but yes, that's the idea. More precisely, not when you want to
change the Exchange, you cannot do that, but when you want the message processed by the remaining
of the route to be different.
>
> One more thing to keep in mind is that there are 2 kinds of "headers", we call them headers
and properties. The headers are on the message, and normally re not propagated. That means
that if you produce and out, that will have it's own headers, and if you want headers from
the original in to be propagated it's up to you copy them into the new message. The properties
are on the Exchange, and they do get propagated, regardless of a Processor producing an out
or not. That's for instance the place for security credentials, etc.
>
> Not to self: since a picture is worth 1000 words, we need better diagrams on the camel
site.
Thanks for the clarification. I would love to se a pointer in the getIn
and getOut javadocs to a more detailed discussion about the differences
of the two, for example in the package file. Would that be possible?

Regards,
Tarjei


> Cheers,
> Hadrian
>
>
> On Sep 24, 2010, at 9:03 AM, Tarjei Huse wrote:
>
>> Hi,
>> On 09/24/2010 10:36 AM, Claus Ibsen wrote:
>>> I also added a couple of FAQs as well, such as
>>> https://cwiki.apache.org/confluence/display/CAMEL/Using+getIn+or+getOut+methods+on+Exchange
>> Maybe the FAQ item could be flashed out with something like:
>>
>> getIn and getOut are not related to the messaging style used.
>>
>> You should only use getOut() when you change the exchange completely and
>> want all traces of the incomming message (headers etc) removed.
>>
>> ?
>> T
>>
>>>>> /Bengt
>>>>>
>>>>> 2010/9/14 Claus Ibsen <claus.ibsen@gmail.com>
>>>>>
>>>>>> On Tue, Sep 14, 2010 at 2:16 PM, Bengt Rodehav <bengt@rodehav.com>
wrote:
>>>>>>> I think that was very useful information. I hadn't thought of
a Processor
>>>>>> as
>>>>>>> very low level - it's definitely a level that a lot of us will
use. Then
>>>>>> I
>>>>>>> guess that in some circumstances (like when coding a custom processor)
>>>>>> you
>>>>>>> need to set the out messsage if the MEP is "out capable" otherwise
you
>>>>>> just
>>>>>>> set the in message. Are there more situations where this is needed?
>>>>>>>
>>>>>> If the MEP is out capable you can still just change the IN message.
>>>>>> If the OUT is null, then Camel will re-use the IN (which you just
>>>>>> changed) and thus still route whatever you have changed.
>>>>>>
>>>>>> You only need to use OUT if you want to create a totally 100% new
>>>>>> message which is not related to the IN message at all.
>>>>>> And this is only needed in special cases.
>>>>>>
>>>>>> Otherwise you get the problem with: Why do I lose my message headers
etc.
>>>>>>
>>>>>>
>>>>>>
>>>>>>> I think that this subject is definitely complicated enough to
warrant a
>>>>>> good
>>>>>>> documentation somewhere. I think it's really important for developers
to
>>>>>>> understand core concepts instead of just using boilerplate samples
>>>>>> (although
>>>>>>> they are very useful).
>>>>>>>
>>>>>>> /Bengt
>>>>>>>
>>>>>>> 2010/9/14 Claus Ibsen <claus.ibsen@gmail.com>
>>>>>>>
>>>>>>>> On Tue, Sep 14, 2010 at 10:23 AM, Christian Müller
>>>>>>>> <christian.mueller@gmail.com> wrote:
>>>>>>>>> Hello Claus!
>>>>>>>>>
>>>>>>>>> That's not (in my opinion) how it works currently. At
present I work
>>>>>> on a
>>>>>>>>> route which looks like this:
>>>>>>>>>
>>>>>>>>> errorHandler(
>>>>>>>>> defaultErrorHandler()
>>>>>>>>>   .retryAttemptedLogLevel(LoggingLevel.DEBUG)
>>>>>>>>>   .retriesExhaustedLogLevel(LoggingLevel.INFO));
>>>>>>>>>
>>>>>>>>> onException(IllegalArgumentException.class)
>>>>>>>>> .handled(true)
>>>>>>>>> .maximumRedeliveries(0)
>>>>>>>>> .beanRef("myResultProvider", "failureResponse");
>>>>>>>>>
>>>>>>>>> from("cxf:bean:MyCoolService")
>>>>>>>>> .processRef("myValidator") // validates conditional rules
>>>>>>>>> .inOut("direct:mySubroute")
>>>>>>>>> .beanRef("myResultProvider", "successResponse")
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> If my validator throws a IllegalArgumentException and
the result
>>>>>> provider
>>>>>>>>> writes the response into the in message, the web service
will return
>>>>>>>> null.
>>>>>>>>> But if I write the response into the out message, the
web service will
>>>>>>>>> return it. So, I changes my bean to the following "pattern":
>>>>>>>>>
>>>>>>>> Well that could CXF Bean component having a bug.
>>>>>>>>
>>>>>>>> If you decide to use a Processor and work on Exchange then
you use the
>>>>>>>> low level Camel API and then you have to handle the IN/OUT
stuff
>>>>>>>> yourself.
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>> if (exchange.getPattern().isOutCapable()) {
>>>>>>>>> exchange.getOut().setBody(response);
>>>>>>>>> } else {
>>>>>>>>> exchange.getIn().setBody(response);
>>>>>>>>> }
>>>>>>>>>
>>>>>>>>> And that's the same how the
>>>>>>>> org.apache.camel.processor.ConvertBodyProcessor
>>>>>>>>> works (I know you know this, but for the other guys..
:o) )
>>>>>>>>>
>>>>>>>>> public class ConvertBodyProcessor implements Processor
{
>>>>>>>>> ...
>>>>>>>>>   public void process(Exchange exchange) throws Exception
{
>>>>>>>>>       Message in = exchange.getIn();
>>>>>>>>>       if (charset != null) {
>>>>>>>>>           exchange.setProperty(Exchange.CHARSET_NAME,
charset);
>>>>>>>>>       }
>>>>>>>>>       Object value = in.getMandatoryBody(type);
>>>>>>>>>
>>>>>>>>>       if (exchange.getPattern().isOutCapable()) {
>>>>>>>>>           Message out = exchange.getOut();
>>>>>>>>>           out.copyFrom(in);
>>>>>>>>>           out.setBody(value);
>>>>>>>>>       } else {
>>>>>>>>>           in.setBody(value);
>>>>>>>>>       }
>>>>>>>>>   }
>>>>>>>>> ...
>>>>>>>>> }
>>>>>>>>>
>>>>>>>>> Should our custom processors/beans/.. not work in the
same way?
>>>>>>>>>
>>>>>>>>> Cheers,
>>>>>>>>> Christian
>>>>>>>>>
>>>>>>>>
>>>>>>>> --
>>>>>>>> Claus Ibsen
>>>>>>>> Apache Camel Committer
>>>>>>>>
>>>>>>>> Author of Camel in Action: http://www.manning.com/ibsen/
>>>>>>>> Open Source Integration: http://fusesource.com
>>>>>>>> Blog: http://davsclaus.blogspot.com/
>>>>>>>> Twitter: http://twitter.com/davsclaus
>>>>>>>>
>>>>>>
>>>>>> --
>>>>>> Claus Ibsen
>>>>>> Apache Camel Committer
>>>>>>
>>>>>> Author of Camel in Action: http://www.manning.com/ibsen/
>>>>>> Open Source Integration: http://fusesource.com
>>>>>> Blog: http://davsclaus.blogspot.com/
>>>>>> Twitter: http://twitter.com/davsclaus
>>>>>>
>>>>
>>>> --
>>>> Claus Ibsen
>>>> Apache Camel Committer
>>>>
>>>> Author of Camel in Action: http://www.manning.com/ibsen/
>>>> Open Source Integration: http://fusesource.com
>>>> Blog: http://davsclaus.blogspot.com/
>>>> Twitter: http://twitter.com/davsclaus
>>>>
>>>
>>
>> -- 
>> Regards / Med vennlig hilsen
>> Tarjei Huse
>> Mobil: 920 63 413
>>


-- 
Regards / Med vennlig hilsen
Tarjei Huse
Mobil: 920 63 413


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