Introducing ASP.NET MVC

Alan Dean

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

othersPerl has Catalyst, Gantry, Jifty and

othersPHP 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”

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 HTTP API

GET /GET /page.html

POST /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

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

PUT

The 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

DELETE

The DELETE method requests that the origin server delete the resource

identified by the Request-URI.

Idempotent

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 REST

Hypertext is standardizedfewer UIs

Identification is standardizedless communication

Exchange protocols are standardizedfewer integrations

Interactions are standardizedfewer semantics

Data formats are standardizedfewer 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)

Linkshttp://del.icio.us/tag/aspnetmvc

http://code.google.com/p/alan-dean/http://code.google.com/p/altnetuk/

Emailalan.dean@thoughtpad.net

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