在 Saga 中发布消息，其中类型仅在运行时已知

Question

I want to publish a message from a Saga where the messgae type is not known compile time, only runtime. So far i've only found methods for publishing a message with generic signature - i cannot find any where i can publish a runtime type.

I'm in the works of modifying the Sample-Batch application https://github.com/MassTransit/Sample-Batch to be able to batch any message type

How Sample-Batch is configured

Initially(
    When(BatchJobReceived)
        .Then(context => Touch(context.Saga, context.Message.Timestamp))
        .Then(context => SetReceiveTimestamp(context.Saga, context.Message.Timestamp))
        .Then(Initialize)
        .PublishAsync(context => context.Init<ProcessBatchJob>(new
        {
            BatchJobId = context.Saga.CorrelationId,
            InVar.Timestamp,
            context.Saga.BatchId,
            context.Saga.OrderId,
            context.Saga.Action
        }))
        .TransitionTo(Received));

What i want to accomplish

1. Receive the BatchJobReceived message
2. Deserialize the inner message Json using InnerMessageAsString and InnerMessageType
3. Store the inner message on the state
4. Publish the inner message And then keep state of the messages when they return

Initially(
    When(BatchJobReceived)
        .Then(context => Touch(context.Saga, context.Message.Timestamp))
        .Then(context => SetReceiveTimestamp(context.Saga, context.Message.Timestamp))
        .Then(Initialize)
        .Then(context => DeserializeInnerMessage(context.Saga, context.Message))
        .PublishAsync(context => context.Init(context.Saga.InnerMessage, context.Saga.InnerMessageType))
        .TransitionTo(Received));

static void DeserializeInnerMessage(BatchJobState state, BatchJobReceived job)
{
    var innerMessageType = Type.GetType(job.InnerMessageType);
    var innerMessage = JsonConvert.DeserializeObject(job.InnerMessageAsString, innerMessageType);

    state.InnerMessage = innerMessage;
}

There are however no context.Init() methods taking a Type parameter, it solely have a generic signature context.Init<>() .

How do i accomplish this? Or any other approaches more suitable?

Answer 1

There isn't one, you can use your own ThenAsync statement to publish an unknown type as object :

.ThenAsync(x => x.Publish(x.Saga.InnerMessage, x.Saga.InnerMessageType)