Understanding RESTful WebService

q REST (Representational State Transfer) is a simple stateless architecture that generally runs over HTTP.

q REST is an architectural style, and an approach to communicate that is often used in the development of Web Services.

q REST provides a set of design rules for creating stateless services that identifies resources by their unique URIs. A client accesses the resource using the URI, acts upon them using a standardized fixed set of methods, and a representation of the resource is returned. 

q When using the HTTP protocol to access RESTful resources, the resource identifier is the URL of the resource and the standard operation to be performed on that resource is one of the HTTP methods: GET, PUT, DELETE, POST, HEAD.

q The amazing thing about the REST is the fact that clients (browsers) and servers can interact in complex ways without the client knowing anything beforehand about the server and the resources it hosts.

q An API that adheres to the principles of REST does not require the client to know anything about the structure of the API. Rather, the server needs to provide whatever information the client needs to interact with the service. The client provides the location of the resource with all required fields, and server will send the matching resource details.

The following principles encourage RESTful applications to be simple, lightweight, and fast:

Ø Resource identification through URI(Uniform Resource Identifiers):

     Resources are identified by URIs, which provide a global addressing space for resource (Noun)

Ø Self-descriptive messages: Resources are decoupled from their representation so that their content can be accessed in a variety of formats, such as HTML, XML, plain text, PDF, JPEG, JSON, and others.

Ø Stateless interactions through hyperlinks: Every interaction with a resource is stateless; that is, request messages are self-contained. Stateful interactions are based on the concept of explicit state transfer. Several techniques exist to exchange state, such as URI rewriting, cookies. State can be embedded in response messages to point to valid future states of the interaction. 

Ø Uniform interface: Resources are manipulated using a fixed set of four create, update ,read, delete www operations: PUT, POST, GET and DELETE. (Verb)

To create a resource on the server, use POST.
To retrieve a resource, use GET.
To change the state of a resource or to update it, use PUT.
To remove or delete a resource, use DELETE.