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From Brian McCallister <bri...@apache.org>
Subject Pluggable Stomp Message Mapping (was: [stomp-dev] PHP Stomp Client)
Date Tue, 19 Sep 2006 03:17:14 GMT
(Replying at top as it is a long message :-)

The mapping be configured by naming a "converter" of some kind in the  
activemq.xml

This is a bit tricksier than it might be because the activemq.xml is  
just a specialized spring config which reads a lot of stuff from a  
URL syntax, and adding Java classnames in a URL is the ick.

I've started poking around and my current plan is to pull the AMQ  
message creating and Stomp message creation bits out of the protocol  
converter and use an implementation of some mapping interface to do  
the conversion.

Exactly what the interface needs to look like I am not sure yet. In  
order to handle largish messages, it should probably deal with  
DataInput (AMQ's stream/buffer+channel hiding thing) instances, but  
we'll have had to already parse the type to get this far, so it may  
be a case of doing some parsing of the headers, and passing the data  
input in to be munged, or it may fall out that something else is more  
useful.

For encoding AMQ to stomp, we are faced with something similar -- we  
pass in the JMS message, which might be a stream message with a large  
body, we probably want to be able to "chunk" it out, that means  
either making a stomp frame abstraction which can read from a stream  
and is returned by the converter, or having the converter actually  
"send" the message on the wire. Not sure which I like more.

Thoughts?

-Brian

On Sep 18, 2006, at 7:45 AM, Dejan Bosanac wrote:

> Thanks James.
>
>
>>
>> We've a Stomp transport for ActiveMQ which is here...
>> http://incubator.apache.org/activemq/maven/activemq-core/xref/org/ 
>> apache/activemq/transport/stomp/package-summary.html
>>
>> which can currently deal with all the stomp messages nicely. Maybe  
>> you
>> mean to extend that? Or did you have something else in mind?
>>
>
>
> In one of his comments Brian said that he plans to create pluggable
> handling framework for stomp messages for ActiveMQ 4.1.
>
> Following that idea, I have even found a discussion on this topic
>
> http://mail-archives.apache.org/mod_mbox/geronimo-activemq-dev/ 
> 200606.mbox/% 
> 3Caf2843cd0606131045k1084ec85qd337a076af47c363@mail.gmail.com%3E
>
> which is related to handling of ByteMessages.
>
>
> I thought that this is exactly what I would like to have for handling
> of this kind of "map" messages. As I see it, it would be the best to
> extend functionality of the
>
> public  ActiveMQMessage convertMessage(StompFrame command)
>
> method in the
>
> org.apache.activemq.transport.stomp.ProtocolConverter
>
> class
>
> I can add hard-coded mapping for this special case, or as Brian said,
> introduce some additional flexibility by allowing developers to submit
> their own converter classes at this point. Who knows what other
> "protocol" on top of Stomp someone would be interesting to create in
> the future (or what kind of object serialization/deserialization to
> perform).
>
> The only thing that I'm not sure of is how these plugins would be  
> configured.
>
> In any case, I won't start doing any work on this before we agree on
> how this functionality should look like, or whether it is necessary to
> make any changes at all.
>
> Dejan
>
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