rest.elkstein.orgLearn REST: A Tutorial

A fast-training course for REST - Re presentational S tate T ransfer, a new approach to systems architecture and a lightweight alternative to web services 1. What is REST? REST stands for Re presentational S tate T ransfer. (It is sometimes spelled "ReST".) It relies on a stateless, client-server, cacheable communications protocoland in virtually all cases, the HTTP protocol is used. REST is an architecture style for designing networked applications. The idea is that, rather than using complex mechanisms such as CORBA, RPC or SOAP to connect between machines, simple HTTP is used to make calls between machines. In many ways, the World Wide Web itself, based on HTTP, can be viewed as a REST-based architecture. RESTful applications use HTTP requests to post data (create and/or update), read data (e.g., make queries), and delete data. Thus, REST uses HTTP for all four CRUD (Create/Read/Update/Delete) operations. REST is a lightweight alternative to mechanisms like RPC (Remote Procedure Calls) and Web Services (SOAP, WSDL, et al.). Later, we will see how much more simple REST is. Despite being simple, REST is fully-featured; there’s basically nothing you can do in Web Services that can’t be done with a RESTful architecture. REST is not a "standard". There will never be a W3C recommendataion for REST, for example. And while there are REST programming frameworks, working with REST is so simple that you can often "roll your own" with standard library features in languages like Perl, Java, or C#. By Dr. M. Elkstein 50 comments 2. REST as Lightweight Web Services As a programming approach, REST is a lightweight alternative to Web Services and RPC. Much like Web Services, a REST service is: Platform-independent (you don’t care if the server is Unix, the client is a Mac, or anything else), Language-independent (C# can talk to Java, etc.), Standards-based (runs on top of HTTP), and Can easily be used in the presence of firewalls. Like Web Services, REST offers no built-in security features, encryption, session management, QoS guarantees, etc. But also as with Web Services, these can be added by building on top of HTTP: For security, username/password tokens are often used. For encryption, REST can be used on top of HTTPS (secure sockets). ... etc. One thing that is not part of a good REST design is cookies: The "ST" in "RE ST " stands for "State Transfer", and indeed, in a good REST design operations are self-contained, and each request carries with it (transfers) all the information (state) that the server needs in order to complete it. By Dr. M. Elkstein 10 comments 3. How Simple is REST? Let’s take a simple web service as an example: querying a phonebook application for the details of a given user. All we have is the user’s ID. Using Web Services and SOAP, the request would look something like this: ?xml version="1.0"? soap:Envelope xmlns:soap="http://www.w3.org/2001/12/soap-envelope" soap:encodingStyle="http://www.w3.org/2001/12/soap-encoding" soap:body pb="http://www.acme.com/phonebook" pb:GetUserDetails pb:UserID12345/pb:UserID /pb:GetUserDetails /soap:Body /soap:Envelope (The details are not important; this is just an example.) The entire shebang now has to be sent (using an HTTP POST request) to the server. The result is probably an XML file, but it will be embedded, as the "payload", inside a SOAP response envelope. And with REST? The query will probably look like this: http://www.acme.com/phonebook/UserDetails/12345 Note that this isn’t the request bodyit’s just a URL. This URL is sent to the server using a simpler GET request, and the HTTP reply is the raw result datanot embedded inside anything, just the data you need in a way you can directly use. It’s easy to see why Web Services are often used with libraries that create the SOAP/HTTP request and send it over, and then parse the SOAP response. With REST, a simple network connection is all you need. You can even test the API directly, using . I have developed dozens of web sites, and have taught numerous programming and computer science courses in academia and in the industry. I provide consultancy services, and my clients range from small startups to the largest banks in my country. View my complete...