Short introduction to REST

REST is a simple way to organize interactions between independent systems.

REST is a simple way to organize interactions between independent systems. It’s been growing in popularity since 2005. This is due to the fact that REST allows you to interact with minimal overhead with clients as diverse as mobile phones and other websites. In theory, REST is not tied to the web, but it’s almost always implemented as such, and was inspired by HTTP. As a result, REST can be used wherever HTTP can.

REST stands for Representational State Transfer. (It is sometimes spelled “ReST”.) It relies on a stateless, client-server, cacheable communications protocol — and 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.

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.).

  • 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 recommendation 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#.

While REST is not a standard, it does use standards:

  • HTTP
  • URL
  • XML/HTML/GIF/JPEG/etc (Resource Representations)
  • text/xml, text/html, image/gif, image/jpeg, etc (MIME Types)

Let’s take a simple web service as an example: querying a phonesnumbersbook 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.phones.numbers.com/phonebook">
 <pb:GetUserDetails>
  <pb:UserID>U56789</pb:UserID>
 </pb:GetUserDetails>
</soap:Body>
</soap:Envelope>

 

(The details are not important; this is just an example.) The entire request body 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.phones.numbers.com/phonebook/UserDetails/U56789

Note that this isn’t the request body — it’s just a URL. This URL is sent to the server using a simpler GET request, and the HTTP reply is the raw result data — not 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 your browser.

 

Leave a Reply