In this post to his site Paul Jones looks at the combination of the Action-Domain-Responder pattern and the Command Bus pattern in application development. In the post he answer the question about how they fit together.

Over the past few weeks, different people have asked me where a Command Bus goes in an Action-Domain-Responder system. While I’m not a DDD expert, after brushing up on the subject a little, my answer is: "In the Domain."

He starts by reviewing the three pieces of the ADR pattern with brief descriptions of each. The then covers the Command Bus pattern, linking to several other resources with more details about the pattern itself and a quick summary of their main points. He talks about how the overall structure is a part of the Command Query Responsibility Segregation pattern and suggests that, since the Command Bus pattern is a "fire and forget" kind of thing it belongs in the Domain of ADR. He gives a brief code example and answers other questions about validation and error handling as a part of this suggested flow.

Paul Jones has written up a post talking about service classes, payloads and responders and how they can help pull logic out of controllers and into more reusable chunks. It's inspired by comments and methods mentioned in another earlier post from Revath Kumar.

Revath Kumar has a good blog post up about extracting domain logic from controllers and putting that logic in a service class. After reading it, I commented that with a little extra work, it would be easy to modify the example to something closer to the Action-Domain-Responder pattern. In doing so, we would get a better separation of concerns (especially in presentation).

Paul applies some of the concepts that Revath outlined to the ADR pattern, suggesting that service classes should always return Payloads and the reduction of functionality in the controller overall. He includes an example of what the resulting code would look like, following along with the "orders" scenario outlined in Revath's post.

Paul Jones has written up a post talking about service classes, payloads and responders and how they can help pull logic out of controllers and into more reusable chunks. It's inspired by comments and methods mentioned in another earlier post from Revath Kumar.

Revath Kumar has a good blog post up about extracting domain logic from controllers and putting that logic in a service class. After reading it, I commented that with a little extra work, it would be easy to modify the example to something closer to the Action-Domain-Responder pattern. In doing so, we would get a better separation of concerns (especially in presentation).

Paul applies some of the concepts that Revath outlined to the ADR pattern, suggesting that service classes should always return Payloads and the reduction of functionality in the controller overall. He includes an example of what the resulting code would look like, following along with the "orders" scenario outlined in Revath's post.

Paul Jones has a new post with more information about his proposed "Action-Domain-Responder" design pattern (a replacement for the typical MVC) and suggests a new piece, the Domain Payload pattern. This pattern would use a domain payload object to wrap the data and provide the responder with additional handling and context.

In Action-Domain-Responder the Action passes input to the Domain layer, which then returns some data for the Action to pass to the Responder. In simple scenarios, it might be enough for the Responder to inspect the data to determine how it should present that data. In more complex scenarios, though, it would make more sense for the Domain to pass back the data in a way that indicates the status of the data. Instead of the Responder inspecting the Domain results, the Domain should tell us what kind of results they are.

He shows a code example of this Domain Payload object in action, starting with some typical MVC code and refactoring it along the way into an ADR structure. He shifts from a typical model into a more domain-driven approach and describes the wrapping of the data in the payload, context for the contents (even just a class name helps) and how those relate to the actual output. You can find the resulting code in this example over on Paul's GitHub account.

In his latest post Paul Jones comes back to his proposed application structure, the idea of Action-Domain-Responder, and answers some questions about where content negotiation happens and routing.

While talking about Action-Domain-Responder on the Crafting Code Tour, one of the common questions I got was: “Where does content negotiation happen?” My response was always: “Where does it happen in Model-View-Controller?” That opened up a discussion on how content negotiation is a tricky bit that can go in different places, depending on how you want the concerns separated, and is not a problem specific to ADR.

He goes on and tries to answer the question a bit better, pointing out that "it's a problem for everyone" isn't really good enough to take action on. He works through the different pieces of the ADR pattern, trying to reason out where the right fit is. He suggests a "first filter" on the Controller level, more specifically at the Router level. That's not to say that the Router needs to know about content handling, but it does need to know how to pass that information on.

In his most recent post Matthew Weier O'Phinney shares his own spin on the Action-Domain-Responder pattern (from Paul Jones): how the controllers in the ARD setup could be explained as facades.

Paul M. Jones has started an interesting discussion rethinking the MVC pattern as applied to the web, which he has dubbed Action-Domain-Responder (ADR). If you haven't given it a read yet, click the link and do that; this page will still be sitting here waiting when you return. I agree with a ton of it - heck, I've contributed to it a fair bit via conversations with Paul. But there's been one thing nagging at me for a bit now, and I was finally able to put it into words recently. Controllers - Actions in ADR - can be explained as facades.

Matthew starts off by defining the Facade design pattern with a quote from the infamous "Gang of Four" book: simply put, a simplified interface to a complex system. He provides a basic example of a facade that wraps some common steps for inserting and logging data with this kind of simplified interface. He applies this to the ADR pattern's controllers, pointing out that it handles a few complex steps "behind the scenes" common to marshaling and managing the request.

For me, thinking of Controllers and Actions as Facades has an additional benefit: it describes rather complex architectural patterns in terms of basic design patterns. I find the more I can reduce the complexity of a definition, the more likely I will understand and use it correctly.

Paul Jones has a new post to his site today with a more in-depth look at his proposed "Action-Domain-Responder" design pattern and how to refactor an application, based on some with with the Aura framework, to use it.

The v1 version of the Aura framework includes a controller to handle web assets. The idea for this controller was that an Aura package might have images, scripts, and stylesheets that need to be publicly available, but in development you don’t necessarily want to copy them to a public document root every time you change them. [...] That v1 version is a mess. The Controller handles the response-building entirely, and there is no Model separation at all. Let’s try refactoring it to an Action-Domain-Responder architecture and clean it up some for a v2 version.

Associated code it just linked to, but he does summarize the steps needed to make the transition: extract the domain logic, move responses to a separate class and rename the controller to an action. He also shows how making this separation makes testing easier and links to examples of tests for each. He finishes the post with two final notes about the refactor. One points out that this method isn't the only way to handle this architecture shift and that the action returns a responder, not a response object.