/* Part of SWI-Prolog Author: Jan Wielemaker E-mail: J.Wielemaker@vu.nl WWW: http://www.swi-prolog.org Copyright (C): 1985-2014, University of Amsterdam VU University Amsterdam This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this library; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA As a special exception, if you link this library with other files, compiled with a Free Software compiler, to produce an executable, this library does not by itself cause the resulting executable to be covered by the GNU General Public License. This exception does not however invalidate any other reasons why the executable file might be covered by the GNU General Public License. */ :- if(current_predicate(is_dict/1)). :- module(http_json, [ reply_json/1, % +JSON reply_json/2, % +JSON, Options reply_json_dict/1, % +JSON reply_json_dict/2, % +JSON, Options http_read_json/2, % +Request, -JSON http_read_json/3, % +Request, -JSON, +Options http_read_json_dict/2, % +Request, -Dict http_read_json_dict/3 % +Request, -Dict, +Options ]). :- else. :- module(http_json, [ reply_json/1, % +JSON reply_json/2, % +JSON, Options http_read_json/2, % +Request, -JSON http_read_json/3 % +Request, -JSON, +Options ]). :- endif. :- use_module(http_client). :- use_module(http_header). :- use_module(http_stream). :- use_module(json). :- use_module(library(option)). :- use_module(library(error)). :- use_module(library(lists)). :- use_module(library(memfile)). :- multifile http_client:http_convert_data/4, http_client:post_data_hook/3, json_type/1. :- predicate_options(http_read_json/3, 3, [ content_type(any), false(ground), null(ground), true(ground), value_string_as(oneof([atom, string])), json_object(oneof([term,dict])) ]). :- predicate_options(reply_json/2, 2, [ content_type(any), status(integer), json_object(oneof([term,dict])), pass_to(json:json_write/3, 3) ]). /** HTTP JSON Plugin module This module inserts the JSON parser for documents of MIME type =|application/jsonrequest|= and =|application/json|= requested through the http_client.pl library. Typically JSON is used by Prolog HTTP servers. This module supports two JSON representations: the classical representation and the new representation supported by the SWI-Prolog version 7 extended data types. Below is a skeleton for handling a JSON request, answering in JSON using the classical interface. == handle(Request) :- http_read_json(Request, JSONIn), json_to_prolog(JSONIn, PrologIn), (PrologIn, PrologOut), % application body prolog_to_json(PrologOut, JSONOut), reply_json(JSONOut). == When using dicts, the conversion step is generally not needed and the code becomes: == handle(Request) :- http_read_json_dict(Request, DictIn), (DictIn, DictOut), reply_json(DictOut). == This module also integrates JSON support into the http client provided by http_client.pl. Posting a JSON query and processing the JSON reply (or any other reply understood by http_read_data/3) is as simple as below, where Term is a JSON term as described in json.pl and reply is of the same format if the server replies with JSON. == ..., http_post(URL, json(Term), Reply, []) == @see JSON Requests are discussed in http://json.org/JSONRequest.html @see json.pl describes how JSON objects are represented in Prolog terms. @see json_convert.pl converts between more natural Prolog terms and json terms. */ %% http_client:http_convert_data(+In, +Fields, -Data, +Options) % % Hook implementation that supports reading JSON documents. It % processes the following option: % % * json_object(+As) % Where As is one of =term= or =dict=. If the value is =dict=, % json_read_dict/3 is used. http_client:http_convert_data(In, Fields, Data, Options) :- memberchk(content_type(Type), Fields), is_json_type(Type), !, ( memberchk(content_length(Bytes), Fields) -> setup_call_cleanup( ( stream_range_open(In, Range, [size(Bytes)]), set_stream(Range, encoding(utf8)) ), json_read_to(Range, Data, Options), close(Range)) ; set_stream(In, encoding(utf8)), json_read_to(In, Data, Options) ). is_json_type(Type) :- json_type(Type), !. is_json_type(ContentType) :- json_type(Type), sub_atom(ContentType, 0, _, _, Type), !, strip_utf8(ContentType, Plain), json_type(Plain). :- if(current_predicate(is_dict/1)). json_read_to(In, Data, Options) :- memberchk(json_object(dict), Options), !, json_read_dict(In, Data, Options). :- endif. json_read_to(In, Data, Options) :- json_read(In, Data, Options). %% strip_utf8(+ContentTypeIn, -ContentType) is det. % % Strip an optional =|; charset=UTF-8|=. JSON data is always % UTF-8, but some clients seem to insist in sending this. strip_utf8(ContentType, Plain) :- sub_atom(ContentType, B, _, A, ;), sub_atom(ContentType, _, A, 0, Ext), normalize_space(atom(Charset), Ext), downcase_atom(Charset, 'charset=utf-8'), !, sub_atom(ContentType, 0, B, _, CT), normalize_space(atom(Plain), CT). strip_utf8(ContentType, ContentType). %% json_type(?MIMEType:atom) is semidet. % % True if MIMEType is a JSON mimetype. http_json:json_type/1 is a % multifile predicate and may be extended to facilitate % non-conforming clients. json_type('application/jsonrequest'). json_type('application/json'). %% http_client:post_data_hook(+Data, +Out:stream, +HdrExtra) is semidet. % % Hook implementation that allows http_post_data/3 posting JSON % objects using one of the forms below. % % == % http_post(URL, json(Term), Reply, Options) % http_post(URL, json(Term, Options), Reply, Options) % == % % If Options are passed, these are handed to json_write/3. In % addition, this option is processed: % % * json_object(As) % If As is =dict=, json_write_dict/3 is used to write the % output. This is default if json(Dict) is passed. % % @tbd avoid creation of intermediate data using chunked output. :- if(current_predicate(is_dict/1)). http_client:post_data_hook(json(Dict), Out, HdrExtra) :- is_dict(Dict), !, http_client:post_data_hook(json(Dict, [json_object(dict)]), Out, HdrExtra). :- endif. http_client:post_data_hook(json(Term), Out, HdrExtra) :- http_client:post_data_hook(json(Term, []), Out, HdrExtra). http_client:post_data_hook(json(Term, Options), Out, HdrExtra) :- option(content_type(Type), HdrExtra, 'application/json'), setup_call_cleanup( ( new_memory_file(MemFile), open_memory_file(MemFile, write, Handle) ), ( format(Handle, 'Content-type: ~w~n~n', [Type]), json_write_to(Handle, Term, Options) ), close(Handle)), setup_call_cleanup( open_memory_file(MemFile, read, RdHandle, [ free_on_close(true) ]), http_post_data(cgi_stream(RdHandle), Out, HdrExtra), close(RdHandle)). :- if(current_predicate(is_dict/1)). json_write_to(Out, Term, Options) :- memberchk(json_object(dict), Options), !, json_write_dict(Out, Term, Options). :- endif. json_write_to(Out, Term, Options) :- json_write(Out, Term, Options). %% http_read_json(+Request, -JSON) is det. %% http_read_json(+Request, -JSON, +Options) is det. % % Extract JSON data posted to this HTTP request. Options are % passed to json_read/3. In addition, this option is processed: % % * json_object(+As) % One of =term= (default) to generate a classical Prolog % term or =dict= to exploit the SWI-Prolog version 7 data type % extensions. See json_read_dict/3. % % @error domain_error(mimetype, Found) if the mimetype is % not known (see json_type/1). % @error domain_error(method, Method) if the request is not % a =POST= or =PUT= request. http_read_json(Request, JSON) :- http_read_json(Request, JSON, []). http_read_json(Request, JSON, Options) :- select_option(content_type(Type), Options, Rest), !, delete(Request, content_type(_), Request2), request_to_json([content_type(Type)|Request2], JSON, Rest). http_read_json(Request, JSON, Options) :- request_to_json(Request, JSON, Options). request_to_json(Request, JSON, Options) :- option(method(Method), Request), option(content_type(Type), Request), ( data_method(Method) -> true ; domain_error(method, Method) ), ( is_json_type(Type) -> true ; domain_error(mimetype, Type) ), http_read_data(Request, JSON, Options). data_method(post). data_method(put). data_method(patch). :- if(current_predicate(is_dict/1)). %% 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) :- http_read_json_dict(Request, Dict, []). http_read_json_dict(Request, Dict, Options) :- merge_options([json_object(dict)], Options, Options1), http_read_json(Request, Dict, Options1). :- endif. %% reply_json(+JSONTerm) is det. %% reply_json(+JSONTerm, +Options) is det. % % Formulate a JSON HTTP reply. See json_write/2 for details. % The processed options are listed below. Remaining options are % forwarded to json_write/3. % % * content_type(+Type) % The default =|Content-type|= is =|application/json; % charset=UTF8|=. =|charset=UTF8|= should not be required % because JSON is defined to be UTF-8 encoded, but some % clients insist on it. % % * status(+Code) % The default status is 200. REST API functions may use % other values from the 2XX range, such as 201 (created). % % * json_object(+As) % One of =term= (classical json representation) or =dict= % to use the new dict representation. If omitted and Term % is a dict, =dict= is assumed. SWI-Prolog Version 7. :- if(current_predicate(is_dict/1)). reply_json(Dict) :- is_dict(Dict), !, reply_json_dict(Dict). :- endif. reply_json(Term) :- format('Content-type: application/json; charset=UTF-8~n~n'), json_write(current_output, Term). :- if(current_predicate(is_dict/1)). reply_json(Dict, Options) :- is_dict(Dict), !, reply_json_dict(Dict, Options). :- endif. reply_json(Term, Options) :- reply_json2(Term, Options). %% 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. :- if(current_predicate(is_dict/1)). reply_json_dict(Dict) :- format('Content-type: application/json; charset=UTF-8~n~n'), json_write_dict(current_output, Dict). reply_json_dict(Dict, Options) :- merge_options([json_object(dict)], Options, Options1), reply_json2(Dict, Options1). :- endif. reply_json2(Term, Options) :- select_option(content_type(Type), Options, Rest0, 'application/json'), ( select_option(status(Code), Rest0, Rest) -> format('Status: ~d~n', [Code]) ; Rest = Rest0 ), format('Content-type: ~w~n~n', [Type]), json_write_to(current_output, Term, Rest).