MSDN Magazine - January 2009 - (Page 93)

Jon FlAndERS Service Station An Introduction To RESTful Services With WCF This is the first in a series of columns about building Windows Communication Foundation (WCF) services using the architectural style known as Representational State Transfer (REST). You could say that 2009 will be the year of REST here in the Service Station column, and it’s long overdue in my opinion. REST has been a popular style for many years since its introduction in 2000. In this first column, I want to discuss some of the basic tenets of REST, as well as present an implementation of a RESTful service using WCF. In future columns, I’ll dig into more details of the base ideas of REST, as well as technologies that are built on that base. An architectural style is a set of constraints that can be applied when building something. And an architectural style of software is something that describes the features that can be used to guide the implementation of a software system. REST is an architectural style that can be used to build software in which clients (user agents) can make requests of services (endpoints). REST is one way to implement a client-server architectural style—in fact, REST explicitly builds on the client-server architectural style. A man named Roy Thomas Fielding first coined the term REST as a concept in his PhD dissertation (ics.uci.edu/~fielding/pubs/dissertation/top.htm). He was one of the people who worked on the specifi- which is designated using the HTTP Content-Type header. (XHTML, XML, JPG, PNG, and JSON are some well-known media types.) • Resources are self-descriptive. All the information necessary to process a request on a resource is contained inside the request itself (which allows services to be stateless). • Resources contain links to other resources (hyper-media). A service that uses the architectural style of REST is generally referred to as a RESTful service or endpoint. Just to get a feeling for the ideas behind this architectural style, I’m going to present a An Abstract Example Learning about REST REST can be used to build software in which clients can make requests of services. small example. Imagine I needed to build a service to work with the data behind MSDN Magazine—a service that could tell me all of the years MSDN Magazine has been published and each of the articles in each issue. Let’s say the requirement is that the editors of the magazine could use this service to add new articles and manage the data for upcoming issues. When building RESTful services, you can go through a very simple set of basic steps to design your service: 1. What are your resources going to be? 2. What are the URIs that are going to be used to represent those resources? 3. What parts of the uniform interface (HTTP verbs) is each URI going to support? These are the basic building blocks of a RESTful endpoint: resources and their representations, URIs for those resources, and the parts of the uniform interface to which each URI will respond. There are more advanced features you can take advantage of, such as more Send your questions and comments to sstation@microsoft.com. Code download at code.msdn.microsoft.com/mag200901Service. January 2009 93 cation that drives most of the Internet today: Hypertext Transfer Protocol (HTTP). Normally the background of the people describing an architectural style isn’t relevant to a discussion of the style, but here I think it is important because I believe one of the best ways to get a basic understanding of REST is to think about the Web and how it works. I have to assume you, as a developer, are familiar with (and probably, like me, are a heavy daily addict/user of) the Web. Arguably, the Web can be regarded as the largest, most scalable, and most popular distributed application of all time. The constraints of REST are based on the same underlying principles that govern the Web. Those principles are: • User agents interact with resources, and resources are anything that can be named and represented. Each resource can be addressed via a unique Uniform Resource Identifier (URI). • Interaction with resources (located through their unique URIs) is accomplished using a uniform interface of the HTTP standard verbs (GET, POST, PUT, and DELETE). Also important in the interaction is the declaration of the resource’s media type, http://ics.uci.edu/~fielding/pubs/dissertation/top.htm http://ics.uci.edu/~fielding/pubs/dissertation/top.htm http://code.msdn.microsoft.com/mag200901Service

Table of Contents Feed for the Digital Edition of MSDN Magazine - January 2009

Toolbox CLR Inside Out Basic Instincts Cutting Edge Test Run First Look� Geneva Framework Silverlight Windows Mobile Service Station Security Briefs Extreme ASP.NET Foundations .NET Matters { End Bracket }

MSDN Magazine - January 2009

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