MassTransit generic message mis-typing

[Jeff]

I am running into a base-typing problem with messages I am attempting
to publish through MassTransit. Consider the following:

public abstract class Event : CorrelatedBy<Guid> {

public Guid CorrelationId { get; set; }

public abstract string EventName { get; }

public override string ToString() {
return string.Format("{0} - {1}", EventName,
CorrelationId);
}

}


public class PersonCreated : Event {

public PersonCreated(Guid personId, string firstName, string
lastName) {

PersonId = personId;
FirstName = firstName;
LastName = lastName;

}

public readonly Guid PersonId;
public readonly string FirstName;
public readonly string LastName;

}


However, when I attempt to publish a collection of abstract events
with something like:

public void PublishEvents(IEnumerable<Event> events) {

foreach (var e in events) {

Bus.Instance.Publish(e);

}

}

I do NOT receive any events out of this collection, regardless of
their concrete types. If I cast the event to its proper concrete type
before publishing on the bus, I do receive the message properly.

Any ideas as to how I can correct this to allow my abstract collection
of Events to be processed without casting each one?

[Jeff]

I have attempted to convert to using the BinarySerializer, and I still
see the same behavior. The only way I can get the PersonCreated Event
to appear is to explicitly cast the event before calling Bus.Publish

Jeff

[Nik Govorov]

Hi Jeff.

I guess it is by design. You are using generic method Publish<T>, so message type extracted from T.

In your case you can write your own bus extension method that uses FastInvoker from magnum.

    public static class ServiceBusEx

    {

        public static UnTypedMessagePublishingExtension Extensions(this IServiceBus self)

        {

            return new UnTypedMessagePublishingExtension(self);

        }

    }

    public class UnTypedMessagePublishingExtension

    {

        private IServiceBus bus;

        public UnTypedMessagePublishingExtension(IServiceBus bus)

        {

            this.bus = bus;

        }

        public void Publish(object message)

        {

            this.FastInvoke(new[] {message.GetType()}, "Publish", message);

        }

        protected void Publish<T>(T message) where T : class

        {

            bus.Publish(message, ctx => { });

        }

    }

Usage:

bus.Extensions().Publish(new SubMessage {Name = "Jeff"});

[Dru Sellers]

What does your subscription code look like?

-d

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[Dru Sellers]

Hi Nik, you are correct. MassTransit depends heavily on the message type for message routing. I am not sure what it is you are trying to accomplish Jeff with the base class.  Care to explain?

-d

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[Jeffrey Fritz]

I am using a base Event class to ensure that all of my events that I publish are CorrelatedBy<Guid> as well as to ensure several required properties that I did not disclose here.  

I am using an event source, and would like to be able to ensure that only Event objects are saved, not Command objects.

Consequently, I have an block of code I am working with that looks something like:

public static void Dispatch(Commit c) {

    foreach (var e in c.Events) {

        Bus.Instance.Publish(e);

    }

}

... and the event that is published is of the base class Event, not the concrete PersonCreated type.

I have tried Nik's recommendation, and the data is now flowing properly.


Jeff

[Nik Govorov]

Hi Dru, Jeff just wants to have non-generic version of the 'Publish' method to determine message type in 'runtime'.

[Dru Sellers]

Jeff, care to wrap up your publish method up into an extention method and send a pull request. 

-d

On Aug 30, 2011, at 9:50 AM, Nik Govorov <nikita....@gmail.com> wrote:

Hi Dru, Jeff just wants to have non-generic version of the 'Publish' method to determine message type in 'runtime'.

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[Chris Patterson]

I've got one ready to commit, just need to get back to bandwidth land. 

It's basically the same. 

--

Chris Patterson

[Jeffrey Fritz]

It sounds like you beat me to it...  If you still need it later this evening, I'll submit a pull request.

Jeff