.net and other musings

Ben Lovell, an agile developer living in the UK.

Category: Monorail

Incremental development with Monorail: Part Seven

Since our last installment I slipped in a ninja-edit to one of the configuration files. This was to ensure that our sole service was marked as transient rather than the default Windsor lifestyle of singleton. This was pointed out to me by an eagle-eyed commenter and was an oversight on my part. So we’re now at rev10 and ready to roll once again!

In our last post we tidied up a few bits and improved our code-base rather than actually adding features as such. This time we’re going to move down into the persistence and start to drive out this notional layer.

We’re going to handle data access using the repository pattern. The repositories will work on our ActiveRecord entities ensuring they’re persisted to our database. We will introduce a new interaction between our service BlogPostService and the newly introduced repository interface IBlogPostRepository. Let’s get on and write a test:

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The test above is fairly self-explanatory. We’ve introduced the IBlogPostRepository and we’re passing it into our BlogPostService which should then call the Save method passing our mapped post. We need to get rid of the red code and get the test passing, so first we must create our new interface, and then modify the service constructor:

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We need to modify our other tests that construct the BlogPostService as they’re still assuming only a single argument constructor exists. As we have some duplication going on we’ll push this construction up into our setup code:

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We should be able to run our tests in this fixture now:

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As expected, since our BlogPostService doesn’t actually do much with our repository yet, we need to do some pretty minor tweaking to pass this test:

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Let’s try again now:

77  Cool, let us try and run the whole suite including our integration type tests:

78

The integration tests are failing as we’ve yet to map the new dependency in our Windsor configuration. We can specify this now:

79

We still have failing integration tests though, so we need to add the BlogPostRepository specified in our configuration:

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As you can see it doesn’t do much, but we just want our tests passing at this stage. Let’s run the whole suite of tests now:

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Great, we have a working product once more. I’m going to finish here, as ever, the latest changes have been committed:

http://code.google.com/p/mr-blogengine/

Next time we’ll make our new repository more useful and finally hit the database!

Incremental development with Monorail: Part Six

We finished up in part five with a full suite of passing tests and our BlogPostService is slowly taking shape now. The next few posts will introduce persistence and validation but before we get started on these features, we have a little housekeeping to perform on our existing code.

First step is to build the Castle trunk and update our references to the latest versions. Secondly, we’ll incorporate a few changes suggested by Hammett.

After building and replacing our references with the latest Castle build I’ll run the tests as a sanity check before we proceed:

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With that out of the way our first code change will ensure we play nicely with HTTP. It is considered good practice to ensure requests which update or create resources is carried out via POST – so we can modify our only PostController.Save action to ensure this is so but before we do this we’ll write a test:

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Running our test produces the following:

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We’ll modify our Save action now to ensure we only accept the POST verb:

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We have added the AccessibleThrough attribute and explicitly specified that our action must only allow the POST verb. We’ll run our test again and make sure everything is working as expected:

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The next step is to modify our add.vm view to use the helper methods to generate our form tags. We’ve done that and once again we’ll run our tests:

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I’m noticing a little duplication creeping in to our integration tests that should be removed. Also, until now we’ve had to assume that a web server is running on a specific port on our development machine in order to run the integration tests. Through a little tweaking we can spin-up a temporary server in our test fixture setup code and host our test code there instead.

First we add the WebDev.WebHost.dll to our lib project directory and ensure we’re referencing this from the testing project. The next step is to create an app.config file in the testing project so we can configure where and from which port our testing server should be hosting from:

66  Now we add some setup code for the fixture:

67

We’ll also make sure we bring the server down when we’re finished:

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Now ensure the VS web server is not running on the same port, then we can run our tests and make sure our latest changes work out:

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Now, since we specify the web root and port through configuration, we should also use these configurable values to determine the URLs in our tests:

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You can see our tests now call BuildTestUrl to determine the full URL where we’re hosting the development server. Neat. I’m sure when we add further integration fixtures we’ll extract class this, but for now we have a nice working set of tests and should remember the principle of YAGNI!

I’m going to cut this installment short here. In the next post we’ll get back into the swing of it and continue implementing features.

As ever, the latest code has been checked in and is available here:

http://code.google.com/p/mr-blogengine/

MVC Storefront

Rob Conery has been posting a series of screencasts featuring the development of an ASP.NET MVC based product catalogue. This is being carried out in a “TDD” like fashion. The interesting difference between his posts and mine (apart from the obvious fact that I’m lazy and haven’t screencasted… yet) is that he starts from the bottom of the stack and works upwards towards the UI where as I do the opposite.

Its interesting contrasting the two approaches not to mention the differences between the ASP.NET MVC framework and Castle Monorail way of getting things done.

Incremental development with Monorail: Part Five

Welcome back. In this post I’ll be getting our tests passing again and cleaning things up a little. We left off with a failing integration test:

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I suspect this is due to the IBlogPostMapper dependency we introduced to our BlogPostService not being handled by the container. If we run in the browser we can confirm this is in fact true:

As we’ve yet to implement our IBlogPostMapper we must go ahead and do this before we can add the container configuration to pass our integration test. Lets bust out a test and get things rolling:

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We have a few blanks to fill in in order to get this to compile and run:

  1. Make the DTO’s properties virtual so we can mock them. This is in preference to extracting an interface.
  2. Implement IBlogPostMapper.
  3. Add the necessary properties to the IBlogPost interface.

Lets go ahead and do this now:

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IBlogPostMapper minimal implementation:

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The necessary modifications to IBlogPost:

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Now we can compile and run our test:

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Our BlogPostMapper implementation is throwing an exception so lets go back and take another step to try and pass our test:

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BlogPost:

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I’m pretty certain we’ve done enough to pass our test now. Lets have a go:

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OK now lets focus on the full suite:

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Our integration test is still bombing but as we’ve got a mapper now, we can go ahead and wire up our Windsor configuration and get things moving again:

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We’ve added another configuration file: mapper.config and referenced this from the web.config. We shouldn’t need to do any more than this so lets run our full test suite:

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Our full suite is passing now. Not bad for 5 minutes work! As usual the latest changes are checked in to the Google code project hosted here.

Now we have a full passing suite, in our next edition I’ll be moving down into the persistence and also incorporating a few modifications from Hammett. Stay tuned!

Incremental development with Monorail: Part Four

We finished up in the last instalment by moving down a layer into our newly introduced BlogPostService. Our tests are passing yet our application is still pretty lacking in the actual functionality department. To move things on a stage further we need to:

  1. Map from the AddPostRequestDto to our actual BlogPost aggregate root.
  2. Validate the BlogPost.
  3. Persist our new BlogPost.

We need to write another test to flesh out the interaction between our service and something that can map from the DTO to our BlogPost:

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We’re now expecting the BlogPostService to accept the mapper in its constructor, and defining an interaction between the service and the mapper. Before we can get this to compile we need to make a few more changes to our test fixture:

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We’ve modified an existing test to allow for our new dependency and performed some setup tasks. We’ve introduced the IBlogPostMapper and IBlogPost interfaces by way of our test. Running the test causes the compiler to choke so lets go ahead and implement what we need to pass the tests:

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39

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Lets go ahead and run our BlogPostServiceFixture tests:

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Righteo, that went well. For the sake of completeness lets run our full test suite:

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The integration test is failing as we’ve yet to wire up the BlogPostService dependencies in the container. Before we can do this we need to drive out the interfaces we’ve introduced. We’ll do that in the next post.

Incremental development with Monorail: Part Three

Part One
Part Two

In the last instalment we finished up with a suite of passing tests. However, we’ve yet to produce anything remotely usable so lets continue by reaching down further and driving out our services/persistence. We’ll start by writing the following test:

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We’ve meddled with our test setup a little to introduce the MockRepository for mocking out our PostController’s new dependency on the IBlogPostService. Our test now calls the AddPost method on our service interface and sets up the resulting AddPostResponseDto. Running the test produces a bunch of compiler whinging so we best implement the newly introduced bits:

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25 

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These are the only changes and additions we’ve made in order for the tests to compile and run. Running our test now produces the following result:

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As we’ve yet to modify the PostController.Save(…) call to include a call the newly introduced IBlogPostService dependency. Lets go ahead and do this now:

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We’ve now included the call to our newly introduced service and we set the responseMessage if the response is signaled as successful. Lets run our test now:

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It works, ship it! Actually no, again we’re pretty low on actual functionality right now. Remember we’ve yet to actually drive out any implementation of the IBlogPostService interface as yet and I expect that the acceptance test will fail horribly since we didn’t wire up the necessary container configuration either. Lets go ahead and run the whole test suite and see what gives:

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In the brief moments the browser appears during the test we can see the following:

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Hmm, as I predicted earlier our application fails to run due to the lack of proper container configuration. Before we can do this we need to implement the IBlogPostService interface somewhere. We need to write a failing test to begin our foray into the implementation of a BlogPostService:

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Lets create the BlogPostService only performing the steps necessary to pass the test above:

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Run the test:

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Now we have a working BlogPostService we can now wire up our container configuration to pass the acceptance test:

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Now running the full suite of tests produces the following:

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Our tests pass!

That’s it for this post. I’ve checked in the latest changes to the repository. In the next post we’ll continue our efforts and begin to implement validation on our screen-bound DTO’s.

Google code hosted project: http://code.google.com/p/mr-blogengine/

Incremental development with Monorail: Part Two

Part one can be found here.

So in part one we had finished up at a failing test. Lets recap what this was:

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And our failing test:

9

Our add view assumes that a Save action exists on our PostController. In attempting to make the test above pass, we will introduce this new action. However, this will be driven out from the PostController’s test fixture like so:

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We’re faced with a bunch of unimplemented types and members shown in red thanks to Resharper’s error highlighting. As you can see from the test we’ve introduced the AddPostRequestDto and the three properties it exposes. Secondly we’ve introduced the Save action to the PostController that accepts our AddPostRequestDto. Our test then simply asserts that the correct response was set and that the postcreated view is displayed.

Our first step is the implementation of the AddPostRequestDto. Thankfully Resharper will perform this for us:

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We’ve added this new type to the Core project under a new Messages namespace and folder for organisation.

Lets now go ahead and implement the new Save action on the PostController:

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As you can no doubt see, we’ve done only the simplest thing possible to pass the test. Lets run our tests and see the results:

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Well our controller fixtures pass nicely. I’ve got a sneaky suspicion that our acceptance test might fail however:

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The expected confirmation was not displayed! We can assume this is as we’ve yet to create the postcreated view and spat back the responseMessage from this. Lets go ahead and create the view now:

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If I run the test again, in the very short time the browser is visible I can see that we’re failing with an exception occurring during the Monorail binding. To fix this we need to derive the PostController  from Monorail’s SmartDispatcherController and add the DataBind attribute to the Save action’s only parameter:

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So lets go ahead and run our whole test suite:

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Sweet! How functional our application is at this stage is still pretty debatable but we’re getting there :)

Our next task is to actually step down a layer and introduce a service to handle our persistence. I’ve checked in the latest changes. Stay tuned for the next post.

The google code hosted project: http://code.google.com/p/mr-blogengine/

Incremental development with Monorail

EDIT: This is hosted in a google code project accessible from here: http://code.google.com/p/mr-blogengine/

 

This is the first of a series of posts I’m penning where I’ll be incrementally developing a basic blog engine running on the Castle trunk and developed wholly test first.

Each new feature or addition will be described by simple narrative, followed by some testing/coding from the UI (or controller in this case) down to the database.

I’ll be using much of the Castle stack goodness including Monorail, Windsor and ActiveRecord. Unit testing with Mbunit and acceptance testing with Watin.

My aim with this series of posts is to demonstrate the power of the Castle stack, combined with TDD and the slow, incremental addition of features. After each post I’ll check in my latest changes which will after a clean build will result in a fully working system.

project-structure

I’ve completed a small amount of scaffolding up-front for brevity:

  • Castle built from trunk
  • Solution and project structure
  • Basic configuration of Monorail and Windsor

As you can see from the right, our solution consists of three projects. The core project will hold our domain model, interfaces, services and application code. There is a test project for both our unit tests and acceptance tests, and finally we have the web application project holding our controllers, views and static content. I’ve put together a basic layout and stylesheet that serve our needs for now. This will be added to as our blog engine matures.

Although we have no concrete examples as yet, the controllers, services, facilities and configuration properties are configured through Windsor XML configuration files in the web project. We’re running on a Castle build I ran locally after checking out the trunk some point over the last couple of days.

It will be interesting to see how our initial design adapts as required when features are piled on during the later stages of development. I’ve not got any specific plans on how long this series will go on for although I am considering moving my blog away from WordPress and will most likely host under the very blog engine I’ll be creating. Good times! Anyway enough of this, lets move on to the first iteration.

 

 

Iteration 1: Create a Post

For this iteration we will build our first cut at the blog post authoring screen. This comprises a very basic form allowing the author to specify the title, short description and full content of the post. I think you’ll agree that what we’re building in this iteration won’t serve as a fully powered blog engine any time soon, but lets restate our initial aim here: to incrementally build and adapt our system as new requirements and features emerge. With that said, lets get on to building our first feature!

Our first test:

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From our basic requirement we’re now driving out the PostController. This test simply gets our controller into a good state for testing, handily provided by Monorail’s BaseControllerTest and our first test method asserts that when the Add action is called on our controller the correct view is rendered. As you can see from the grab above there is a lot of red code. Resharper is highlighting the members we’ve yet to implement. I attempted to run this test but the compiler chokes. Time to do what we need to pass this test:

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Well that was simple enough. Lets run our test and see the result:

Test Results

As expected, the test now passes. However, there are some serious issues with our controller and the related Monorail configuration:

  1. The controller has no associated layout.
  2. We’ve yet to create the requisite view: Add.vm.
  3. We’ve not added the Windsor XML configuration for our controller.

Before we can do anything to remedy the issues above we’ll need to write a failing test. I’m going to use Watin to create a test which flexes Monorail a little more. Currently our only test relies heavily on most of the controller dependencies being stubbed/mocked out by the BaseControllerTest class. We’ll need to test through the browser to ensure our controller and view/layout are wired up correctly:

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As you can see above we’ve crafted a very simplistic test which asserts that the text “Ben Lovell’s Blog” is found in the browser at the specified URL. Note also that our test assumes the application is running at localhost on port 16489. I’ve configured this in the web application properties so we just need to ensure that the VSNET web development server is running on this port for our application. Lets run the test:

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As expected it fails. To pass this test we need to perform the three steps mentioned earlier. To do this we first add the Layout attribute to the controller and specify the default layout, the contents of which are shown here:

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Next we create an empty view: Add.vm in the views/post folder, and finally we wire up the XML configuration for our controller in the controllers.config file as shown below:

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Lets try and run the test now:

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Now we’re making progress! Lets extend our test a little more now. This time we will find the title, description and content fields, enter some values and submit the form. Asserting that the confirmation message was displayed telling the user their post was saved:

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A few things have changed here: we’ve altered the naming of the test to clarify intent, and as mentioned previously our test will enter some values into our form fields and submit the form. Our last assertion is checking that the correct confirmation message is displayed. Now we could argue that the setting of the description and content is superfluous in this test as the outcomes aren’t asserted. But, the effort required to implement those fields is minimal and highly unlikely to impact on any existing code/tests (i.e. none!).

Lets run the test and see the outcome:

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Our test complains that the “Add Post” text was not found. Lets go and fiddle with our view:

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Good to go, lets run the test:

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Hmm, the first two asserts are passing but now we’re failing on unfound input: post.Title. Time to add the form and fields to the view, we’re going to make a slight jump and include the description and content inputs in our view also:

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Re run the test:

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It fails as we have yet to create the save action on the controller, and also the nonexistent action doesn’t display the required confirmation… For obvious reasons.

At this stage I’m going to wrap this up for now. Part two will follow over the next couple of days. Stay tuned!

Front-end DTO’s

An interesting discussion was brought up in one of the ALT.NET groups regarding the use of DTO’s in the presentation layer that I had to chime in on.

I’m a strong advocate of message passing from the UI to your services for several reasons:

  1. Test driving from the top-down is my favoured approach when developing web applications. I’ll start by writing a failing test for my controller (you should know by now I use Monorail ;)). Then I’ll stub out any dependencies, these usually being service interfaces which accept and return simple DTO’s with absolutely no behaviour. Stubbing out the services allows you to return dummy data very early on in your development. The nice thing about this approach is you can get a working UI together very quickly and then drive out the development of each layer until you hit your domain model. From which point you can then wire-up your real service and repository implementations and satisfy your acceptance tests end-to-end. Now I’m not suggesting that this approach isn’t possible without DTO’s but it makes it a heck lot easier in my experience.
  2. DDD aggregates by their very nature are composed of behaviours you don’t want to pass into your UI. Using DTO’s for binding into your UI keeps things nice and lightweight. Cohesion is high as the DTO’s are created for a very specific purpose, usually to satisfy a particular screen or UI workflow.
  3. I had made the rather nebulous statement that the use of DTO’s insulates your UI against changes in your domain model. Quite rightly somebody replied saying that this was all relative and there are many means to insulate against change. Of course, I wholeheartedly agree but in my defence I was replying to the OP from my iPhone. Now for me to explain this a little… Unless you’re using query projections (a la NHibernate) you’ll be mapping from your domain entities to specific DTO’s using some kind of mapper class. Your mapper probably depends on the interfaces of your particular domain entities and the implementation of your DTO’s. I say implementation as I drive out the mapping using state-based testing, which of course makes perfect sense when mapping from one state to another! Using DTO’s means our controller has a nice seam between itself and the services through their interfaces thus the controller (read: UI) has no knowledge of the domain model at all. Any changes to the domain model are catered for by changing the mapper specific to the affected messages. I won’t get into versioning messages, mainly because I haven’t got the time or inclination :)
  4. I’ve always thought (and I read this somewhere I think, but can’t remember where) that a sign of a well designed architecture, among other things of course, is the ability to replace the UI and have everything function correctly. Now it was probably more poetic than that but essentially what this means is your UI should have absolutely zero dependencies on anything below your service interfaces. Using DTO’s and message passing means the only work your controllers are doing is scraping the request, passing your message to a service and binding the response. I’ve demonstrated this in systems I’ve developed by providing an API (which can be considered another UI if you squint a little and look sideways) which is comprised of exactly the same service calls and DTO’s my web UI is using.
  5. My last point isn’t specifically tied to the use of DTO’s but more based around messaging architecture in general… What this gives me from the very beginning (i.e. the first test) is a nice basis for distributing my architecture. Our services can be hosted on an application server separately from our web application  or preferably located transparently via a message bus which brings in a whole heap of nice side-effects…

So in summary you can see I’m a big fan of the domain model in my services, mapping to and from DTO’s in my UI. What is your favoured approach?

Screen casts coming soon

My plan is to build a basic blogging engine using Castle Monorail, Windsor, ActiveRecord and developed with DDD & TDD. I’ll screencast the whole procedure from start to finish, outlining the basic story or stories for each screencast episode and then go ahead and implement those stories.

Due to the (potential) size of this I’ll no doubt split this up over many screencasts – probably weighing in at around an hour or so per piece. Production values will be conspicuously low of course and the screencasts are not necessarily meant to serve as an educational tool, more a window into my usage of tools & techniques.

I’ll spike out the solution bootstrapping and structure before the first screencast rather than bore you with the requisite stuff. Anyway, expect the first bunch of stories to appear some point early next week…

The Day of Reckoning?

… OK perhaps not. Anyway, today is the supposed release date of the first CTP of the new Microsoft System.Web.MVC framework. As you’ve no doubt seen in previous posts this is a pretty big deal to me.

I’m putting the final touches on a fairly big project right now and have a smaller (internal) one lined up which would be a perfect candidate for testing out System.Web.MVC. Lets see how it stacks up against Monorail…

ASP.NET Development Landscape

With all the System.Web.Mvc goodness flying around at the moment, the Microsoft or nothing shops (you know, the ones that flat-out can’t adopt a technology unless it comes from the borg) might finally get a taste of how web development should be done. Unfortunately for the aforementioned reason, Monorail has never be an option for those developers.

The one thing that really excites me about MSMVC is the periphery of concepts that will be introduced by way of association: deep testability, SRP, DIP and SoC. Traditionally these practices aren’t promoted (or I might go so far as say easily achieved) heavily in the .NET technologies and frameworks coming out of Microsoft. As we’re focusing on ASP.NET at the moment, sure, they’re possible to adhere to whether you’re using ASP.NET in the presentation layer or not, but ASP.NET doesn’t promote them the same way the MVC framework will.

I can’t help but wonder how different the landscape might be now if MSMVC was released with .NET 1.0 instead of webforms?

Handling Missing Controllers

Monorail provides us with the concept of a rescue to handle exceptional circumstances that might occur when processing a request. Rescues can be attached to specific exception types by specifying particular attributes on your controllers. Rather than go into that in this post I’d recommend you take a look here.

You probably noticed the nasty message you get when requesting nonexistent controller:

error

Luckily, Monorail provides an explicit rescue for these circumstances. All you need to do to enable this is add a 404.vm or 404.brail to the /views/rescues directory depending on your choice of view engine.

Microsoft MVC Framework

Some of you may be aware of the ALT.net conference going on this weekend. I wasn’t particularly interested in a gathering of egos in mutual back-slapping, but I was interested in the announcement of the System.Web.MVC framework from Microsoft.

This has been on the cards for a while and had kinda been announced a while back by Scott Guthrie. Since then not much detail has been uncovered other than a one or two hires for the dev team (from what I’ve heard from my sources ;))

Jeffrey Palermo announced some of the technical details in this blog post, although light in actual substance, yet giving us more idea than anything released previously.

Some of the key things of note:

  • Testability: the key concern. Overcome by making everything virtual/behind interfaces and extension points abound.
  • Ability to plug-in to framework via aforementioned extension points. Gives us the ability to add extra view-engines a la Monorail.
  • Default view-engine implementation using ASPX without postback and viewstate pain.
  • Controllers can be resolved from a container i.e. Windsor, Spring.net etc.

A CTP is due towards the end of the year (Monorail will suffice just fine until, and probably far after then) and the framework is slated for release with VS2008 as an add-on to the general release.

Some of the things I’ll be interested in seeing are whether the following are supported:

  • Handling devices, i.e. sniffing user agent and providing different views. Something just recently provided in patch form to Monorail.
  • The MSMVC equivalent of Monorail’s ViewComponent concept.
  • Routing and URL rewriting support.
  • Monorail Helper equivalent.
  • AJAX support.

It has been mentioned that some of the plumbing may be used to reduce the Monorail codebase. Now that could be interesting…

Updating without trashing associations

Monorail provides a handy means of binding parameters to controllers from several different sources including: querystring, posted items etc via the DataBind attribute. However, if you’re attempting to bind an entity with associations you’ll quickly find that the associations aren’t loaded as part of the usual binding process.

To ensure your associations are loaded as part of the binding process – with the caveat that you’re using ActiveRecord based persistence you must use the ARDataBind attribute. It really is as simple as specifying your binding preference and this attribute and the associations are loaded by magic… Well not exactly magic, but by the ActiveRecordMediator. Example:

public void Save([ARDataBind("product", AutoLoad = AutoLoadBehavior.NewInstanceIfInvalidKey)] Product product)

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