This is an ihmplementation of CRUD pattern for manipulate resources, this is the first step to use the HTTP protocol as an application protocol instead of a transport protocol.

Restbuck Protocol

Verb	URI or template	Use
POST	/order	Create a new order, and upon success, receive a Locationheader specifying the new order's URI.
GET	/order/{orderId}	Request the current state of the order specified by the URI.
PUT	/order/{orderId}	Update an order at the given URI with new information, providing the full representation.
DELETE	/order/{orderId}	Logically remove the order identified by the given URI.

Resource Represenation

The previous tables shows a contrat, the URI or URI template, allows us to indentify resources, now we will chose a representacion, for this particular case we will use JSON.

Note:

A resource can have multiple URIs.
A resource can have multiple Representations.

RESTBUCKS_SERVER

This class implement the main entry of our REST CRUD service, we are using a default connector (Nino Connector, using a WebServer written in Eiffel). We are inheriting from URI_TEMPLATE_ROUTED_SERVICE, this allows us to map our service contrat, as is shown in the previous table, the mapping is defined in the feature setup_router, this also show that the class ORDER_HANDLER will be encharge of to handle different type of request to the ORDER resource.

class
	RESTBUCKS_SERVER

inherit
	ANY

	URI_TEMPLATE_ROUTED_SERVICE

	DEFAULT_SERVICE
		-- Here we are using a default connector using the default Nino Connector,
		-- but it's possible to use other connector (CGI or FCGI).

create
	make

feature {NONE} -- Initialization

	make
		-- Initialize the router (this will have the request handler and 
		-- their context).
		do
			initialize_router
			make_and_launch
		end

	create_router
		do
			create router.make (2)
		end

	setup_router
		local
			order_handler: ORDER_HANDLER [REQUEST_URI_TEMPLATE_HANDLER_CONTEXT]
		do
			create order_handler
			router.map_with_request_methods ("/order", order_handler, <<"POST">>)
			router.map_with_request_methods ("/order/{orderid}", order_handler, <<"GET", "DELETE", "PUT">>)
		end

feature -- Execution

	execute_default (req: WSF_REQUEST; res: WSF_RESPONSE)
			-- I'm using this method to handle the method not allowed response
			-- in the case that the given uri does not have a corresponding http method
			-- to handle it.
		local
			h : HTTP_HEADER
			l_description : STRING
			l_api_doc : STRING
		do
			if req.content_length_value > 0 then
				req.input.read_string (req.content_length_value.as_integer_32)
			end
			create h.make
			h.put_status ({HTTP_STATUS_CODE}.method_not_allowed)
			h.put_content_type_text_plain
			l_api_doc := "%NPlease check the API%NURI:/order METHOD: POST%NURI:/order/{orderid} METHOD: GET, PUT, DELETE%N"
			l_description := req.request_method + req.request_uri + " is not allowed" + "%N" + l_api_doc
			h.put_content_length (l_description.count)
			h.put_current_date
			res.set_status_code ({HTTP_STATUS_CODE}.method_not_allowed)
			res.write_header_text (h.string)
			res.write_string (l_description)
		end

end

How to Create an order with POST

Here is the convention that we are using: POST is used for creation and the server determines the URI of the created resource. If the request POST is SUCCESS, the server will create the order and will response with 201 CREATED, the Location header will contains the newly created order's URI, if the request POST is not SUCCESS, the server will response with 400 BAD REQUEST, the client send a bad request or 500 INTERNAL_SERVER_ERROR, when the server can deliver the request.

POST /order HTTP/1.1
Host: 127.0.0.1:8080
Connection: keep-alive
Content-Length: 196
Origin: chrome-extension://fhjcajmcbmldlhcimfajhfbgofnpcjmb
Content-Type: application/json
Accept: */*
Accept-Encoding: gzip,deflate,sdch
Accept-Language: es-419,es;q=0.8,en;q=0.6
Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3
	     
{
 "location":"takeAway",
 "items":[
          {
           "name":"Late",
	   "option":"skim",
	   "size":"Small",
	   "quantity":1
	   }
    ]
}

Response success

HTTP/1.1 201 Created
Status	201 Created
Content-Type	application/json
Content-Length	123
Location	http://localhost:8080/order/1
Date	FRI,09 DEC 2011 20:34:20.00 GMT

{
  "location" : "takeAway",
  "status" : "submitted",
  "items" : [ {
    "name" : "late",
    "size" : "small",
    "quantity" : 1,
    "option" : "skim"
  } ]
}

How to Read an order with GET

Using GET to retrieve resource information. If the GET request is SUCCESS, we response with 200 OK, and a representation of the order If the GET request is not SUCCESS, we response with 404 Resource not found If is a Conditional GET and the resource does not change we send a 304, Resource not modifed

GET /order/1 HTTP/1.1
Host: 127.0.0.1:8080
Connection: keep-alive
Accept: */*
Accept-Encoding: gzip,deflate,sdch
Accept-Language: es-419,es;q=0.8,en;q=0.6
Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3
If-None-Match: 6542EF270D91D3EAF39CFB382E4CEBA7

Response HTTP/1.1 200 OK

Status	200 OK
Content-Type	application/json
Content-Length	123
Date	FRI,09 DEC 2011 20:53:46.00 GMT
etag	2ED3A40954A95D766FC155682DC8BB52

{
  "location" : "takeAway",
  "status" : "submitted",
  "items" : [ {
    "name" : "late",
    "size" : "small",
    "quantity" : 1,
    "option" : "skim"
  } ]
}

How to Update an order with PUT

A successful PUT request will not create a new resource, instead it will change the state of the resource identified by the current uri. If success we response with 200 and the updated order. 404 if the order is not found 400 in case of a bad request 500 internal server error If the request is a Conditional PUT, and it does not mat we response 415, precondition failed.

Suposse that we had created an Order with the values shown in the How to create an order with POST But we change our decision and we want to stay in the shop.

PUT /order/1 HTTP/1.1
Content-Length: 122
Content-Type: application/json; charset=UTF-8
Host: localhost:8080
Connection: Keep-Alive
Expect: 100-Continue

{
  "location" : "in shop",
  "status" : "submitted",
  "items" : [ {
    "name" : "late",
    "size" : "small",
    "quantity" : 1,
    "option" : "skim"
  } ]
}

Response success

HTTP/1.1 200 OK
Status	200 OK
Content-Type	application/json
Date	FRI,09 DEC 2011 21:06:26.00 GMT
etag	8767F900674B843E1F3F70BCF3E62403
Content-Length	122

{
"location" : "in shop",
"status" : "submitted",
"items" : [ {
		"name" : "late",
		"size" : "small",
		"quantity" : 1,
		"option" : "skim"
} ]
}

How to Delete an order with DELETE

Here we use DELETE to cancel an order, if that order is in state where it can still be canceled. 204 if is ok 404 Resource not found 405 if consumer and service's view of the resouce state is inconsisent 500 if we have an internal server error

DELETE /order/1 HTTP/1.1
Host: localhost:8080
Connection: Keep-Alive

Response success

HTTP/1.1 204 No Content

Status	204 No Content
Content-Type	application/json
Date	FRI,09 DEC 2011 21:10:51.00 GMT

If we want to check that the resource does not exist anymore we can try to retrieve a GET /order/1 and we will receive a 404 No Found

GET /order/1 HTTP/1.1
Host: localhost:8080
Connection: Keep-Alive

Response

HTTP/1.1 404 Not Found

Status	404 Not Found
Content-Type	application/json
Content-Length	44
Date	FRI,09 DEC 2011 21:14:17.79 GMT

The following resource/order/1 is not found

References

How to get a cup of coffe
[Rest in Practice] (http://restinpractice.com/default.aspx)