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.. -*- mode: rst -*-
.. -*- coding: utf-8 -*-
This is a sample project showing how to process http requests in a safe way in
OCaml.
For example:
- A service using the GET method cannot have any body resquest
- A service using the HEAD method cannot have any body response
Interface
=========
The interface for a service is given in an OCaml module, and is declaring all
the possibles values for a service.
Each service shall describe:
- an URL to the server
- the body of the request
- the body of the response
.. code:: ocaml
type request = { value : string } [@@deriving yojson]
type response = { value : string; nbcar : int64 } [@@deriving yojson]
(** The method used in the service *)
let method_ = Services.POST
type placeholders = unit
(** No placeholder here in the request url *)
(** The path to the service, matching the type parameters *)
let path = Path.(T1 (Fixed (V_string.v "api/counter")))
Here, we are not declaring any implementation, only the types.
Implementation
==============
The server part
---------------
There is no implementation yet, this is done in the server, for example using
`Dream_handler`:
.. code:: ocaml
let handler =
Dream_handler.handle
(module Services_impl.Nb_car)
(fun (() : Services_impl.Nb_car.placeholders) body ->
Lwt.return_ok
Services_impl.Nb_car.
{
value = body.value;
nbcar = Int64.of_int (String.length body.value);
})
As the url is also given in the service interface, we can also create the route:
.. code:: ocaml
let route = Dream_handler.register (module Services_impl.Nb_car) handler
let () =
Dream.run @@ Dream.logger
@@ Dream.router
[
route;
]
The client part
---------------
This example use the library brr to make a request to this service:
.. code:: ocaml
let futr = Js_handler.send (module Services_impl.Nb_car) () { value }
Another example using cohttp :
.. code:: ocaml
let root = "http://[::1]:8080"
let* result =
Cohttp_handler.request ~root
(module Services_impl.Nb_car)
() { value = "foobar" }
|
