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:UserID>12345</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:
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.
- Still, REST libraries (for simplifying things) do exist, and we will discuss some of these later.
Note how the URL’s "method" part is not called "GetUserDetails", but simply "UserDetails". It is a common convention in REST design to use nouns rather than verbs to denote simple resources.