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From "Jim Gomes (JIRA)" <>
Subject [jira] Resolved: (AMQNET-94) Use of AcknowledgmentMode enum and boolean for priority limit use of NMS API for vendor extensions
Date Thu, 07 Aug 2008 00:49:52 GMT


Jim Gomes resolved AMQNET-94.

    Resolution: Won't Fix

It is possible to change the {{IConnection}} interface to use the following generic types
to allow passing in a generic enumeration:
interface IConnection
    ISession CreateSession(System.Enum acknowledgementMode);
    System.Enum AcknowledgementMode { get; set; }

However, I think that it will force more code to be written using explicit casting in order
to deal with the {{AcknowledgementMode}} property in the most general cases.

Since using provider specific acknowledgment modes is the outlyer case, I think using casting
to show specific intent to deviate from standard modes is preferred.  The C# enum type system
is robust enough to support the following using the existing interface definition without
reverting to generic {{System.Enum}}:

{code:borderStyle=solid|title=Sample of Extant Flexibility}
public interface IConnection : IDisposable, IStartable, IStoppable
    ISession CreateSession(AcknowledgementMode acknowledgementMode);
    AcknowledgementMode AcknowledgementMode { get; set; }

enum MyAckModes

IConnection connection = GetConnection();
// Set the default ack mode
connection.AcknowledgementMode = (AcknowledgementMode) MyAckModes.IgnoreDups;
// Set session-specific ack mode
ISession session = connection.CreateSession((AcknowledgementMode) MyAckModes.Explicit);

As can be seen from this snippet of code, the existing code base allows the use of provider
specific enumerations while providing type-safety and non-casting for the general case.  When
a user of NMS wants to have low-level access to a provider's unique acknowledgment modes,
then they can do so and the C# enum system will carry their values through, even if that acknowledgment
mode value is outside the range of the original {{AcknowledgmentMode}} enumeration.  I have
created a sample C# app that demonstrates basic casting of enumerations to show that provider
specific enumeration values can be "carried" inside the existing {{AcknowledgementMode}} enumeration.
 Since these values only make sense to the individual providers, they will be the ones who
will cast when setting/getting the {{AcknowledgementMode}} property.

using System;

public class EnumTest
    enum MyEnum        { First, Second, Third }
    enum ProviderEnum  { Fourth, Fifth }

    static void ShowEnum(System.Enum baseEnum)
        Console.WriteLine("base = {0}", baseEnum);
        ProviderEnum derived = (ProviderEnum) baseEnum;
        Console.WriteLine("derived = {0}", derived);

    static void Main()

When this sample application is run, the following is output:

{panel:title=EnumTest output|borderStyle=solid|bgColor=#FFFFCE}
base = Second
derived = Fifth
base = Third
derived = 2

I hope that this addresses the concerns about using provider specific extensions to the acknowledgment
mode enumeration.  

> Use of AcknowledgmentMode enum and boolean for priority limit use of NMS API for vendor
> --------------------------------------------------------------------------------------------------
>                 Key: AMQNET-94
>                 URL:
>             Project: ActiveMQ .Net
>          Issue Type: Improvement
>          Components: ActiveMQ Client
>            Reporter: Mark Pollack
>            Assignee: Jim Gomes
>            Priority: Minor
>             Fix For: 1.0
> This came up on the dev mailing list.  The AcknowledgmentMode enumeration lists the standard
JMS ack modes.  However, vendors extend that, in particular TIBCO EMS.  This should change
to either an Enum, int, or string type so that the API will be more portable.
> The same issue exists in the IMessageProducer interface with the boolean value for persistent
delivery instead of and int for "DeliveryMode".  TIBCO EMS offers another value for delivery

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