http_server.pl -- HTTP server library

This library combines the core server functionality provided by several libraries that are needed by almost any web server. It exports the commonly used predicates from library(http/thread_httpd), library(http/http_dispatch), library(http/http_wrapper), library(http/http_parameters), library(http/html_write), library(http/http_json), and library(http/http_dyn_workers).

http_server(+Options) is det: Create an HTTP server using http_dispatch/1 for handling requests. See http_server/2 and http_dispatch/1 for details.

Re-exported predicates

The following predicates are exported from this file while their implementation is defined in imported modules or non-module files loaded by this module.

html_meta +Heads is det

This directive can be used to declare that an HTML rendering rule takes HTML content as argument. It has two effects. It emits the appropriate meta_predicate/1 and instructs the built-in editor (PceEmacs) to provide proper colouring for the arguments. The arguments in Head are the same as for meta_predicate or can be constant html. For example:

:- html_meta
    page(html,html,?,?).

reply_html_page(:Head, :Body) is det

reply_html_page(+Style, :Head, :Body) is det

Provide the complete reply as required by http_wrapper.pl for a page constructed from Head and Body. The HTTP Content-type is provided by html_current_option/1.

See also: - reply_html_partial/1 to avoid adding a DOCTYPE, and required outer HTML elements such as <html>.

is_json_content_type(+ContentType) is semidet

True if ContentType is a header value (either parsed or as atom/string) that denotes a JSON value.

http_read_json_dict(+Request, -Dict) is det

http_read_json_dict(+Request, -Dict, +Options) is det

Similar to http_read_json/2,3, but by default uses the version 7 extended datatypes.

http_read_json_dict(+Request, -Dict) is det

http_read_json_dict(+Request, -Dict, +Options) is det

Similar to http_read_json/2,3, but by default uses the version 7 extended datatypes.

reply_json_dict(+JSONTerm) is det

reply_json_dict(+JSONTerm, +Options) is det

As reply_json/1 and reply_json/2, but assumes the new dict based data representation. Note that this is the default if the outer object is a dict. This predicate is needed to serialize a list of objects correctly and provides consistency with http_read_json_dict/2 and friends.

reply_json_dict(+JSONTerm) is det

reply_json_dict(+JSONTerm, +Options) is det

http_parameters(+Request, ?Parms) is det

http_parameters(+Request, ?Parms, :Options) is det

Get HTTP GET or POST form-data, applying type validation, default values, etc. Provided options are:

attribute_declarations(:Goal): Causes the declarations for an attributed named A to be fetched using call(Goal, A, Declarations).
form_data(-Data): Return the data read from the GET or POST request as a list Name = Value. All data, including name/value pairs used for Parms, is unified with Data.

The attribute_declarations hook allows sharing the declaration of attribute-properties between many http_parameters/3 calls. In this form, the requested attribute takes only one argument and the options are acquired by calling the hook. For example:

    ...,
    http_parameters(Request,
                    [ sex(Sex)
                    ],
                    [ attribute_declarations(http_param)
                    ]),
    ...

http_param(sex, [ oneof(male, female),
                  description('Sex of the person')
                ]).

bug: - If both request parameters (?name=value&...) and a POST are present the parameters are extracted from the request parameters. Still, as it is valid to have request parameters in a POST request this predicate should not process POST requests. We will keep the current behaviour as the it is not common for a request to have both request parameters and a POST data of the type application/x-www-form-urlencoded.
In the unlikely event this poses a problem the request may be specified as [method(get)|Request].

http_parameters(+Request, ?Parms) is det

http_parameters(+Request, ?Parms, :Options) is det

Get HTTP GET or POST form-data, applying type validation, default values, etc. Provided options are:

attribute_declarations(:Goal): Causes the declarations for an attributed named A to be fetched using call(Goal, A, Declarations).
form_data(-Data): Return the data read from the GET or POST request as a list Name = Value. All data, including name/value pairs used for Parms, is unified with Data.

    ...,
    http_parameters(Request,
                    [ sex(Sex)
                    ],
                    [ attribute_declarations(http_param)
                    ]),
    ...

http_param(sex, [ oneof(male, female),
                  description('Sex of the person')
                ]).

bug: - If both request parameters (?name=value&...) and a POST are present the parameters are extracted from the request parameters. Still, as it is valid to have request parameters in a POST request this predicate should not process POST requests. We will keep the current behaviour as the it is not common for a request to have both request parameters and a POST data of the type application/x-www-form-urlencoded.
In the unlikely event this poses a problem the request may be specified as [method(get)|Request].

http_current_request(-Request) is semidet

Returns the HTTP request currently being processed. Fails silently if there is no current request. This typically happens if a goal is run outside the HTTP server context.

http_peer(+Request, -PeerIP:atom) is semidet

True when PeerIP is the IP address of the connection peer. If the connection is established via a proxy or CDN we try to find the initiating peer. Currently supports:

Fastly-client-ip
X-real-ip
X-forwarded-for
Direct connections

bug: - The X-forwarded-for header is problematic. According to Wikipedia, the original client is the first, while according to AWS it is the last.

Undocumented predicates

The following predicates are exported, but not or incorrectly documented.