Simple MVC ASP Framework
One of the things I do for me treasure is create custom web applications for SMBs, and often the client already has some infrastructure in place. Often times PHP is available, but sometimes they just have a basic hosting account on a windows box somewhere so the only language available is ASP. I’ve actually had a few gigs lately that needed somewhat complex sites, and they needed to be done is ASP.
I looked around for a framework for ASP. Something like Fusebox. A nice, easy model / view / controller style framework for a bit of modularity, and I couldn’t find anything. Since I will probably be getting more gigs like this, and I hate writing the same code twice, I decided to write my own simple framework. I have no idea if anyone who regularly uses ASP cares about this kind of stuff, but I figured I’d put it out there so people can at least have a base if they want (and at the minimum to document the framework for myself).
If you’ve used Mach-II, Struts, Fusebox, or RoR nothing in the framework will shock or amaze you. It’s designed to be simple and easy with little configuration. Here is how it works.
The basic concept is you create model objects in the Model directory, you create view page(s) in the View directory, and you link them together with a controller page in the, you guessed it, Controller directory. There is no need to create a file anywhere except one of these 3 places, and there is no XML type control file.
A URL variable is passed into the framework that specifies the Controller and the Method to be called. The Controller page (which is not an object) does some work, creates any model objects it needs, and writes it’s output to user defined variables in a Global Scope (more on this in a minute).
For a quick example, the URL http://a.com/index.asp?C=Books.ShowBookForm would call the ShowBookForm method defined in the Books.asp controller. The Books controller can then create any objects and do anything it needs. It can then set it’s output to variables in Session(…) for the view page to display. Finally, it should set Session(“VIEW”) to say what main view page should be used for display.
Now all the controller output is being written to the Session scope, but the framework hijacks the Session scope and turns it into a Request scope. At the end of the request the Session scope is destroyed, so the life cycle of the Session scope only lasts for the duration of the request. I had to do this because it seems the Request scope in ASP is readonly, and the Session scope is the only scope that persists through sub processes. (For session tracking I tend to use a database and cookies to manage the sessions anyway (I’ve found it helps with scalability)).
So on the view page, you can display any controller output by doing things like:
<h1>Hello <%= Session("out.loggedInGuy") %></h1>
Where “out.loggedInGuy” was set by the controller. You can also conditionally include other views (that can show Session(…) variables as well). For example, the controller could set a variable to specify which include should be shown in the “main content” area of the page using Utils.ShowView(view). Like so:
<!-- #include file="../AppCore/Utils.asp" --> ... <div class="mainToolbar"><%= Utils.ShowView("ToolBar.asp") %></div> <div><%= Utils.ShowView(Session("out.content")) %></div> <div class="mainRightSide"><%= Utils.ShowView("RightBar.asp") %></div> ...
The Model, in general, is a single class per file that does something, and the View is a typical ASP page with the Session(…) items put where you want the output to be displayed. The controller is an ASP page that ties them together. I couldn’t figure out how to make them objects and work properly in the sub process (see “Bit More Information”), so I opted to define controller pages as swtich pages (a la old school Fusebox). An example controller page looks like the following (assume it’s named LoginController.asp):
<!-- #include file="../Model/Login.asp" --> <% Select Case Session("METHOD") Case "DoLogin" Dim MyLogin Set MyLogin = new Login MyLogin.DataFile = Session("SERVER_INSTALL_PATH") & "AppDatastorepasswords.dat" UserLevel = MyLogin.DoLogin(Request.Form("username"), Request.Form("password")) If(UserLevel = "ADMIN" Or UserLevel = "USER") Then Session("out.content") = "Forms/Welcome.asp" Else Session("login.error") = "The username or password passed was wrong!" Session("out.content") = "Forms/Login.asp" End If Case "ShowLogin" Session("out.content") = "Forms/Login.asp" End Select Session("VIEW") = "Main" %>
Pretty straight forward. It looks at the passed method, if it’s the DoLogin method it creates a Login object from the Model directory, and tries to login. If it passes, it sets the pages user defined “main area” to a welcome screen, and if it fails, it sets it to the login form (and sets some display able text defined on the login form).
A URL to use the above controller would look like: http://a.com/index.asp?C=LoginController.ShowLogin, and then the form would post to http://a.com/index.asp?C=LoginController.DoLogin.
Speaking of form posts, one more Utils method is Utils.CreateLink(strController, strMethod). This does a bit of work for you when creating links or form postings by making a link to the proper controller / method. For example, our login form that is processed above could look like this:
<!-- #include file="../AppCore/Utils.asp" --> <div class='error'> <%= Session("login.error") %> </div> <form name="login" action="<%= Utils.CreateLink("LoginController","DoLogin") %>" method="post"> User Name: <input type="text" name="username"> Password: <input type="password" name="password"> <input type="Submit" name="submit" value="Login"> </form>
This keeps the form posting link from being hard coded, and allows the form to be reused in other applications. You could also set Session(…) variables for the controller and method parts of the CreateLink method if you were so inclined.
The main parts of the framework. AppCore/Settings.asp has stuff you may want to / need to change. Any new install should review that file and make sure it looks ok.
Here is a quick reference to the main parts of the framework:
Session(“CONTROLLER”) - the controller portion from the url (information only)
Session(“METHOD”) - the method portion from the url (information only)
Session(“VIEW”) - the main view page to use for the request (controllers should set this)
Session(“APP_DEBUG”) - if the application is in debug mode (information only)
Session(“INSTALL_PATH”) - the path to the root of the application from the browsers point of view (information only)
Session(“SERVER_INSTALL_PATH”) - the path to the root of the application from the server file system point of view (information only)
Session(strUserDefined) - any variables that the controller wants / should pass to the view
<!– #include file="AppCore/Utils.asp” –> - to get the Utils object
Utils.AddError(strErrorText) - add a processing error (for display on the error page)
Utils.ShowView(strViewPage) - a page in the View directory
Utils.CreateLink(strController, strMethod) - create a URL to the passed controller and method
Bit More Information
ASP is kind of unusual with includes. You can only include them with <!–#include, and the file is included before it is compiled. That means there is no way to conditionally include a file into the current request. The only thing I found that comes close to a runtime include is the Server.Execute() method. However, this creates a sub process which makes it hard to / not possible to communicate with the parent process which is why I hijacked the Session scope.
Download / License
I am using this framework for non-enterprise, but in need of modularity, ASP applications for SMB. This is not a project per se - it is just something I am using, and I thought others might benefit from it.
This framework is in the Public Domain. You can download the files here. As for installation, you should be able to just unzip them on your server and it should work out of the box.
Oh and it’s called Mv Casp - for MVC ASP. Not very original I know.