What are RESTful Web Services

Question

I\'ve tried to read about what RESTful webservices from Wikipedia etc but I must admit I don\'t get it. There is a film in which Denzell Washington says \"explain it to me like

Answer 1

RESTful services are services that transfer state represntationally, hence the name REpresentational State Transfer. What this actually means is that data is passed in a declarative manner, which is to say, you get what you ask for.

REST is different from SOAP in that it's not a protocol, and there's no formal specification. SOAP was created to simplify data transfer between applications by using a common interface to access functionality remotely. Unfortunately, to work generally, SOAP is quite complicated, and making SOAP requests is not very straight-forward, requiring XML parsing and generation.

Instead, REST relies on Hyper Text Transfer Protocol (HTTP) to do the heavy lifting. Webservers and server scripts are already built around working within HTTP. To make a request using REST is as simple as a URL request, such as visiting a webpage. The API for a RESTful service can reuse any of HTTP's methods and status codes to signal any errors. Instead of accessing data that's stored in a database through fancy queries and special code, RESTful services allow access that's more similar to a standard filesystem.

The key part of RESTful services, is the declarativeness. A request to GET /widgets/109340 is likely going to get you the data for the widget with an id of 109340. I say "likely" because there's no guarantee. It's up to the implementor. The point is that you can glance at the REST request and know what you expect to be returned. With SOAP, it's much harder to tell whether you have a syntax error.

If /widgets/109340 doesn't exist, instead of passing back a message body, with some specific value to state that the content exists, the server can return a 404 Not Found code, and the user will know that the particular ID doesn't exist. If 403 is returned, the user will know that the item exists, but that they don't have permissions to access it. These request response codes are already supported by programs that make URL requests, because they're common to all servers. This makes REST requests much more resilient.

REST is also flexible on the output format, /widgets/109340 could return a JSON object, but there's no reason it can't return binary data, HTML, XML, SVG, Video, or any other data format. A CDN could use a REST API to serve up versioned content which may or may not be stored on the filesystem: GET /jQuery/1.0.0, GET /jQuery/1.7.1, and GET /jQuery/latest are all RESTful requests.

_{I'm going to assume you understand what Simple Object Access Protocol (SOAP) is}