Module http_server

:- use_module(library(http/http_server)).

This library provides an starting point to build HTTP server based applications. It is based on Hyper, which allows for HTTP/1.0, HTTP/1.1 and HTTP/2. However, some advanced features that Hyper provides are still not accesible.

Usage

The main predicate of the library is http_listen/2, which needs a port number (usually 80) and a list of handlers. A handler is a compound term with the functor as one HTTP method (in lowercase) and followed by a Route Match and a predicate which will handle the call.


text_handler(Request, Response) :-
  http_status_code(Response, 200),
  http_body(Response, text("Welcome to Scryer Prolog!")).

parameter_handler(User, Request, Response) :-
  http_body(Response, text(User)).

http_listen(7890, [
  get(echo, text_handler),                 % GET /echo
  post(user/User, parameter_handler(User)) % POST /user/<User>
]).

Every handler predicate will have at least 2-arity, with Request and Response. Although you can work directly with http_request and http_response terms, it is recommeded to use the helper predicates, which are easier to understand and cleaner:

http_headers(Response/Request, Headers)
http_status_code(Responde, StatusCode)
http_body(Response/Request, text(Body))
http_body(Response/Request, binary(Body))
http_body(Request, form(Form))
http_body(Response, file(Filename))
http_redirect(Response, Url)
http_query(Request, QueryName, QueryValue)

Some things that are still missing:

Read forms in multipart format
HTTP Basic Auth
Session handling via cookies
HTML Templating (but you can use Teruel, Marquete or Djota for that)

Browse source code

http_listen(+Port, +Handlers).

Listens for HTTP connections on port Port. Each handler on the list Handlers should be of the form: HttpVerb(PathUnification, Predicate). For example: get(user/User, get_info(User)) will match an HTTP request that is a GET, the path unifies with /user/User (where User is a variable) and it will call get_info with three arguments: an http_request term, an http_response term and User.

http_headers(?Request_Response, ?Headers).

True iff Request_Response is a request or response with headers Headers. Can be used both to get headers (usually in from a request) and to add headers (usually in a response).

http_status_code(?Response, ?StatusCode).

True iff the status code of the response Response unifies with StatusCode.

http_body(?Request_Response, ?Body).

True iff Body is the body of the request or response. A body can be of the following types:

bytes(Bytes) for both requests and responses, interprets the body as bytes
text(Bytes) for both requests and responses, interprets the body as text
form(Form) only for requests, interprets the body as an application/x-www-form-urlencoded form.
file(File) only for responses, interprets the body as the content of a file (useful to send static files).

http_redirect(-Response, +Uri).

True iff Response is a response that redirects the user to the uri Uri.

http_query(+Request, ?Key, ?Value).

True iff there's a query in request Request with key Key and value Value.