Post on 23-Feb-2016
description
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)