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Date: Mon, 16 Aug 2010 16:04:47 -0400 (EDT)
From: "Jim Gomes (JIRA)" <jira+amqnet@apache.org>
To: dev@activemq.apache.org
Subject: [jira] Commented: (AMQNET-271) Add support for a Message
 Transformer to be set in NMS API
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    [ https://issues.apache.org/activemq/browse/AMQNET-271?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=61219#action_61219 ] 

Jim Gomes commented on AMQNET-271:
----------------------------------

Yeah, those look good.  Although, I would change the naming somewhat to ProducerTransformerDelegate and ConsumerTransformerDelegate.  The reason for this is you can have a cleaner name for  the instance variable.  For example:

{code:title=snippet.cs}
interface IMessageConsumer
{
...
   ConsumerTransformerDelegate ConsumerTransformer;
...
}

interface IMessageProducer
{
...
    ProducerTransformerDelegate ProducerTransformer;
...
}
{code}

While I see how the JMS spec is attempting to support a resilient protocol, this change seems to be a departure from the current programming model.  Isn't this something that should be handled internally to the provider implementation itself?  This seems to be exposing a bit of the lower-level message handling up to the application layer.  At what point should the application layer need to deal with message formats?  Wouldn't the application layer just create a message in whatever logical format it needs and then send it?

> Add support for a Message Transformer to be set in NMS API
> ----------------------------------------------------------
>
>                 Key: AMQNET-271
>                 URL: https://issues.apache.org/activemq/browse/AMQNET-271
>             Project: ActiveMQ .Net
>          Issue Type: Improvement
>          Components: ActiveMQ, EMS, MSMQ, NMS, Stomp
>    Affects Versions: 1.3.0
>            Reporter: Timothy Bish
>            Assignee: Timothy Bish
>            Priority: Minor
>             Fix For: 1.4.0
>
>
> Add support in the NMS API for users to set an custom MessageTransformer on the NMS object: 
> IConnectionFactory
> IConnection
> ISession
> IMessageProducer
> IMessageConsumer
> The transformer would be an instance of IMessageTransformer which provides two methods:
> {noformat}
>     /// <summary>
>     /// Interface for a class that can Transform a Message from one type to another either
>     /// before consumption or before sent by a producer.
>     /// </summary>
>     public interface IMessageTransformer
>     {
>         /// <summary>
>         /// Called from an IMessageProducer prior to sending the IMessage, allows the client
>         /// to perform a transformation on the Message prior to it being sent.  This allows a
>         /// client to configure a single Producer to convert a Message to a format that can be
>         /// processed by a specific receiving client.
>         /// </summary>
>         IMessage ProducerTransform(ISession session, IMessageProducer producer, IMessage message);
>         /// <summary>
>         /// Called from an IMessageConsumer prior to dispatching the message to the client either
>         /// by the 'Receive' methods or from the async listener event.  Allows the client to perform
>         /// message pre-processing before some messages are dispatched into the client code.
>         /// </summary>
>         IMessage ConsumerTransform(ISession session, IMessageConsumer producer, IMessage message);
>     }
> {noformat}

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