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http_client.pl -- HTTP client library
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This library provides the four basic HTTP client actions: GET, DELETE, POST and PUT. In addition, it provides http_read_data/3, which is used by library(http/http_parameters) to decode POST data in server applications.

This library is based on http_open/3, which opens a URL as a Prolog stream. The reply is processed by http_read_data/3. The following content-types are supported. Options passed to http_get/3 and friends are passed to http_read_data/3, which in turn passes them to the conversion predicates. Support for additional content types can be added by extending the multifile predicate http_client:http_convert_data/4.

'application/x-www-form-urlencoded'
Built in. Converts form-data into a list of Name=Value terms.
'application/x-prolog'
Built in. Reads a single Prolog term.
'multipart/form-data'
Processed if library(http/http_multipart_plugin) is loaded. This format should be used to handle web forms that upload a file.
text/html|text/xml
Processed if library(http/http_sgml_plugin) is loaded. See load_html/3 for details and load_xml/3 for details. The output is often processed using xpath/3.
application/json|application/jsonrequest
Processed if library(http/http_json) is loaded. The option json_object(As) can be used to return a term json(Attributes) (As is term) or a dict (As is json).
Source http_get(+URL, -Data, +Options) is det
Get data from a URL server and convert it to a suitable Prolog representation based on the Content-Type header and plugins. This predicate is the common implementation of the HTTP client operations. The predicates http_delete/3, http_post/4 and http_put/4 call this predicate with an appropriate method(+Method) option and ---for http_post/4 and http_put/4--- a post(+Data) option.

Options are passed to http_open/3 and http_read_data/3. Other options:

reply_header(-Fields)
Synonym for headers(Fields) from http_open/3. Provided for backward compatibility. Note that http_version(Major-Minor) is missing in the new version.
Source http_delete(+URL, -Data, +Options) is det
Execute a DELETE method on the server. Arguments are the same as for http_get/3. Typically one should pass the option status_code(-Code) to assess and evaluate the returned status code. Without, codes other than 200 are interpreted as an error.
See also
- Implemented on top of http_get/3.
To be done
- Properly map the 201, 202 and 204 replies.
Source http_post(+URL, +Data, -Reply, +Options) is det
Issue an HTTP POST request. Data is posted using http_post_data/3. The HTTP server reply is returned in Reply, using the same rules as for http_get/3.
See also
- Implemented on top of http_get/3.
Source http_put(+URL, +Data, -Reply, +Options)
Issue an HTTP PUT request. Arguments are the same as for http_post/4.
See also
- Implemented on top of http_post/4.
Source http_patch(+URL, +Data, -Reply, +Options)
Issue an HTTP PATCH request. Arguments are the same as for http_post/4.
See also
- Implemented on top of http_post/4.
Source http_read_data(+Request, -Data, +Options) is det
Read data from an HTTP connection and convert it according to the supplied to(Format) option or based on the Content-type in the Request. The following options are supported:
to(Format)
Convert data into Format. Values are:
  • stream(+WriteStream)) Append the content of the message to Stream
  • atom Return the reply as an atom
  • string Return the reply as a string
  • codes Return the reply as a list of codes
form_data(AsForm)
input_encoding(+Encoding)
on_filename(:CallBack)
These options are implemented by the plugin library(http/http_multipart_plugin) and apply to processing multipart/form-data content.
content_type(+Type)
Overrule the content-type that is part of Request as a work-around for wrongly configured servers.

Without plugins, this predicate handles

'application/x-www-form-urlencoded'
Converts form-data into a list of Name=Value terms.
'application/x-prolog'
Converts data into a Prolog term.
Arguments:
Request- is a parsed HTTP request as returned by http_read_request/2 or available from the HTTP server's request dispatcher. Request must contain a term input(In) that provides the input stream from the HTTP server.
Source http_convert_data(+In, +Fields, -Data, +Options) is semidet[multifile]
Multi-file hook to convert a HTTP payload according to the Content-Type header. The default implementation deals with application/x-prolog. The HTTP framework provides implementations for JSON (library(http/http_json)), HTML/XML (library(http/http_sgml_plugin))
Source http_disconnect(+Connections) is det
Close down some connections. Currently Connections must have the value all, closing all connections.
deprecated
- New code should use http_close_keep_alive/1 from library(http/http_open).
Source http:post_data_hook(+Term, +Out, +Options) is semidet[multifile]
Hook to extend the datatypes supported by the post(Data) option of http_open/3. The default implementation supports prolog(Term), sending a Prolog term as application/x-prolog.