Introducing ASP.NET MVC

Introducing ASP.NET MVC

Alan Dean, Senior Technologist

Model-View-Controller (MVC)is a well-known design pattern

The original 1978 implementation is described

in depth in the influential 1992 paper“Applications Programming in Smalltalk-80:How to use Model-View-Controller (MVC)”

by Steve Burbeck

…“the concept of the design pattern in software provides a key to helping

developers leverage the expertise of other skilled architects.”

Grady Booch, 1995

MVC consists of three kinds of objects

The Model is the application object

The View is the screen presentation

The Controller defines the way the user interface reacts to user input

Before MVC, user interface designs tended

to lump these objects together

MVC decouples them toincrease flexibility and reuse

Controller

Model View

In his paperSteve Burbeck describes two variations of

MVC

a passive model and an active model

The passive model is employed when one controller manipulates the model

exclusively

The controller modifies the model and then informs the view that the model has

changed and should be refreshed

The model in this scenario is completely independent of the view and the controller,

which means that there is no means for the model to report changes in its state

Controller View Model

handleEventservice

update

getData

The HTTP protocol is an example of this.

The browser displays the view and responds to user input, but it does not detect changes in the data on

the server.

Only when the browser explicitly requests a refresh is the server

interrogated for changes.

Separation of Concerns (SoC)

Object types become ‘pluggable’

Intra-team dependency is reduced

Testability is enhanced

Application flow can be hard to grok

MVC Web FrameworksJava has Swing, Struts, Grails and others

Perl has Catalyst, Gantry, Jifty and others

PHP has Zend, Zoop, Agavi and othersPython has Django, Gluon, Pylon and

othersRuby on Rails is famously

‘opinionated’

… and .NET?

.NET MVC Web Frameworks

Spring.NEThttp://www.springframework.net/

Maverick.NEThttp://mavnet.sourceforge.net/

MonoRailhttp://www.castleproject.org/monorail/

… and now ASP.NET MVC from Microsofthttp://asp.net/downloads/3.5-extensions/

“The ASP.NET MVC framework is a lightweight, highly testable

presentation framework that is integrated with existing ASP.NET

features, such as master pages and membership-based authentication.

The MVC framework is defined in the System.Web.Mvc namespace and is

a fundamental, supported part of the System.Web namespace”

Demo

Create a new ASP.NET MVC Solution

HTTP Request FlowHTTP Response

GET /Home/Index HTTP/1.1

HTTP Request Route Handler Controller Model View

HTTP Request Flow

public class Global : HttpApplication{ protected void Application_Start(object sender, EventArgs e) { RouteTable.Routes.Add(new Route { Url = "[controller]/[action]/[id]", Defaults = new { action = "Index", id = (string)null }, RouteHandler = typeof(MvcRouteHandler) }); }}

HTTP ResponseRoute HandlerHTTP Request Controller Model View

HTTP Request Flow

public class HomeController : Controller{ [ControllerAction] public void Index() { CompanyInfo companyInfo = new CompanyInfo(); companyInfo.CompanyName = "Your company name here"; RenderView("Index", companyInfo); }}

HTTP ResponseControllerHTTP Request Route Handler Model View

HTTP Request Flow

public class CompanyInfo{ public string CompanyName { get; set; }}

HTTP ResponseModelHTTP Request Route Handler Controller View

HTTP Request Flow

public partial class Index : ViewPage<CompanyInfo>{ }

ResponseView

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Index.aspx.cs" Inherits="MvcApplication.Views.Home.Index" %><html><head> <title><%= this.ViewData.companyName %></title></head><body> <%= Html.ActionLink(“Homepage", "Index", "Home") %> <div>Welcome!</div></body></html>

HTTP Request Route Handler Controller Model

HTTP Request Flow

HTTP/1.1 200 OKContent-Type: text/html

<html><head> <title>Your company name here</title></head><body> <a href="/Home/Index">Index</a> <div>Welcome!</div></body></html>

HTTP Request Route Handler Controller Model View HTTP Response

Wiki

A wiki is software that allows users to create, edit, and link

web pages easily

Ward Cunningham, developer of the first wiki, WikiWikiWeb, originally

described it as

"the simplest online database that could possibly work"

Wiki DatabaseCREATE TABLE [dbo].[PageTable]([Id] int IDENTITY(1,1) NOT NULL,[Guid] uniqueidentifier NOT NULL,[LastModified] datetime NOT NULL,[Removed] datetime NULL,[Title] varchar(255) NOT NULL,[Body] ntext NOT NULL

);

Wiki HTTP APIGET /

GET /page.htmlPOST /pageGET /page/[title]

GET /page/[title].txtGET /page/[title].htmlGET /page/[title].atom

PUT /page/[title]DELETE /page/[title]

GET

The GET method means retrieve whatever information (in the form of

an entity) is identified by the Request-URI.

Safe & Idempotent

GET /Accept: text/html, */*

303 See OtherLocation: http://localhost/page.htmlCache-Control: publicExpires: Thu, 31 Jan 2008 16:00:00 GMT

GET /page.htmlAccept: text/html, */*

200 OKContent-Type: text/htmlCache-Control: publicExpires: Thu, 31 Jan 2008 16:00:00 GMT

<html><head><title>…</title></head><body><form

action="/page" method="post"enctype="application/x-www-form-urlencoded"><input type="text" name="title" maxlength="255" /><textarea name="body" rows="25" cols="80"></textarea><input type="submit" value="Create Page" />

</form></body></html>

POST

The POST method is used to request that the origin server accept the

entity enclosed in the request as a new subordinate of the resource

identified by the Request-URI

POST /pageContent-Type: application/x-www-form-urlencoded

title=Welcome&body=Welcome+to+my+new+wiki.

201 CreatedContent-Type: text/htmlContent-Location: http://localhost/page/WelcomeCache-Control: no-cache

<html><head>

<title>…</title><meta http-equiv="refresh" content="0;url=http://localhost:64701/page/Welcome">

</head><body>…</body></html>

GET /page/WelcomeAccept: text/html, */*

303 See OtherLocation: http://localhost/page/Welcome.html

Cache-Control: publicLast-Modified: Tue, 29 Jan 2008 16:00:00 GMT

Vary: Accept

GET /page/Welcome.htmlAccept: text/html, */*

200 OKContent-Type: text/htmlContent-Location: http://localhost/page/WelcomeCache-Control: publicLast-Modified: Tue, 29 Jan 2008 16:00:00 GMT

<html><head>

<title>…</title><linkhref="http://localhost/page/Welcome.atom"rel="alternate" title="…"type="application/atom+xml" />

</head><body>…</body></html>

GET /page/Welcome.atomAccept: application/atom+xml

200 OKContent-Type: application/atom+xmlContent-Location: http://localhost/page/WelcomeCache-Control: publicLast-Modified: Tue, 29 Jan 2008 16:00:00 GMT

<?xml version="1.0" encoding="utf-8”?><feed xml:lang="en" xmlns="http://www.w3.org/2005/Atom">…<link href="http://localhost:64701/page/Welcome" rel="source" /><link href="http://localhost:64701/page/Welcome.atom" rel="self"

type="application/atom+xml" hreflang="en" title="…" /><link href="http://localhost:64701/page/Welcome.html"

rel="alternate" type="text/html" hreflang="en" title="…" /><link href="http://localhost:64701/page/Welcome.txt"

rel="alternate" type="text/plain" hreflang="en" title="…" /><entry>…</entry></feed>

GET /page/WelcomeAccept: text/plain

303 See OtherLocation: http://localhost/page/Welcome.txtCache-Control: publicLast-Modified: Tue, 29 Jan 2008 16:00:00 GMTVary: Accept

GET /page/Welcome.txtAccept: text/plain

200 OKContent-Type: text/plainContent-Location: http://localhost/page/WelcomeCache-Control: publicLast-Modified: Tue, 29 Jan 2008 16:00:00 GMT

Welcome to my new wiki.

PUTThe PUT method requests that the enclosed entity be stored under the supplied Request-

URI.

If the Request-URI refers to an already existing resource, the enclosed entity SHOULD be considered as a modified

version of the one residing on the origin server.

Idempotent

PUT /page/WelcomeContent-Type: text/plain

Welcome to my new [[wiki]].

204 No ContentCache-Control: no-cache

DELETE

The DELETE method requests that the origin server delete the resource

identified by the Request-URI.

Idempotent

DELETE /page/Welcome

204 No ContentCache-Control: no-cache

REpresentational State Transfer

REST: The Web Used Correctly

A system or application architecture

… that uses HTTP, URI and other Webstandards “correctly”

… is “on” the Web, not tunnelled through it

REST is an Architectural Style

Defines a set of key “constraints”

… that, if met, make an architecture “RESTful”

… with the Web as one example

Equate “REST” with “RESTful HTTP usage”

Stefan Tilkov

Deriving REST

Client-ServerStateless

CacheUniform interfaceLayered system

Code on Demand

“The central feature that distinguishes the REST architectural style from other network-based styles is its emphasis on a uniform interface

between components.”

Roy Fielding

Uniform InterfaceUniform resource identification

A set of well-defined operations for manipulation

A shared set of media-types

Hypertext as the engine of application state

Benefits of RESTHypertext is standardized

fewer UIsIdentification is standardized

less communicationExchange protocols are standardized

fewer integrationsInteractions are standardized

fewer semanticsData formats are standardized

fewer translations

“No matter how hard I try, I still think the WS-* stack is bloated, opaque, and insanely complex. I think it is

going to be hard to understand, hard to implement, hard to interoperate,

and hard to secure.”

Tim Bray (XML Co-inventor)

“If you’re ready for REST I suggest you jump on board right away and

get ahead of the curveYou’ll have to train your developers in

REST principles.You definitely need to provide

guidance to your people.What you want to do is work to the

point where REST becomes the default for all your distributed

applications.”

Anne Thomas Manes (Burton Group)

Introducing ASP.NET MVC

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