1/* Part of SWI-Prolog 2 3 Author: Jan Wielemaker 4 E-mail: J.Wielemaker@vu.nl 5 WWW: http://www.swi-prolog.org 6 Copyright (c) 2007-2015, University of Amsterdam 7 VU University Amsterdam 8 All rights reserved. 9 10 Redistribution and use in source and binary forms, with or without 11 modification, are permitted provided that the following conditions 12 are met: 13 14 1. Redistributions of source code must retain the above copyright 15 notice, this list of conditions and the following disclaimer. 16 17 2. Redistributions in binary form must reproduce the above copyright 18 notice, this list of conditions and the following disclaimer in 19 the documentation and/or other materials provided with the 20 distribution. 21 22 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 23 "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 24 LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 25 FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 26 COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 27 INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 28 BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 29 LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 30 CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31 LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN 32 ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 33 POSSIBILITY OF SUCH DAMAGE. 34*/ 35 36:- if(current_predicate(is_dict/1)). 37:- module(http_json, 38 [ reply_json/1, % +JSON 39 reply_json/2, % +JSON, Options 40 reply_json_dict/1, % +JSON 41 reply_json_dict/2, % +JSON, Options 42 http_read_json/2, % +Request, -JSON 43 http_read_json/3, % +Request, -JSON, +Options 44 http_read_json_dict/2, % +Request, -Dict 45 http_read_json_dict/3 % +Request, -Dict, +Options 46 ]). 47:- else. 48:- module(http_json, 49 [ reply_json/1, % +JSON 50 reply_json/2, % +JSON, Options 51 http_read_json/2, % +Request, -JSON 52 http_read_json/3 % +Request, -JSON, +Options 53 ]). 54:- endif. 55:- use_module(http_client). 56:- use_module(http_header). 57:- use_module(http_stream). 58:- use_module(json). 59:- use_module(library(option)). 60:- use_module(library(error)). 61:- use_module(library(lists)). 62:- use_module(library(memfile)). 63 64:- multifile 65 http_client:http_convert_data/4, 66 http:post_data_hook/3, 67 json_type/1. 68 69:- public 70 json_type/1. 71 72:- predicate_options(http_read_json/3, 3, 73 [ content_type(any), 74 false(ground), 75 null(ground), 76 true(ground), 77 value_string_as(oneof([atom, string])), 78 json_object(oneof([term,dict])) 79 ]). 80:- predicate_options(reply_json/2, 2, 81 [ content_type(any), 82 status(integer), 83 json_object(oneof([term,dict])), 84 pass_to(json:json_write/3, 3) 85 ]). 86 87 88/** <module> HTTP JSON Plugin module 89 90This module inserts the JSON parser for documents of MIME type 91=|application/jsonrequest|= and =|application/json|= requested through 92the http_client.pl library. 93 94Typically JSON is used by Prolog HTTP servers. This module supports two 95JSON representations: the classical representation and the new 96representation supported by the SWI-Prolog version 7 extended data 97types. Below is a skeleton for handling a JSON request, answering in 98JSON using the classical interface. 99 100 == 101 handle(Request) :- 102 http_read_json(Request, JSONIn), 103 json_to_prolog(JSONIn, PrologIn), 104 <compute>(PrologIn, PrologOut), % application body 105 prolog_to_json(PrologOut, JSONOut), 106 reply_json(JSONOut). 107 == 108 109When using dicts, the conversion step is generally not needed and the 110code becomes: 111 112 == 113 handle(Request) :- 114 http_read_json_dict(Request, DictIn), 115 <compute>(DictIn, DictOut), 116 reply_json(DictOut). 117 == 118 119This module also integrates JSON support into the http client provided 120by http_client.pl. Posting a JSON query and processing the JSON reply 121(or any other reply understood by http_read_data/3) is as simple as 122below, where Term is a JSON term as described in json.pl and reply is of 123the same format if the server replies with JSON. 124 125 == 126 ..., 127 http_post(URL, json(Term), Reply, []) 128 == 129 130@see JSON Requests are discussed in http://json.org/JSONRequest.html 131@see json.pl describes how JSON objects are represented in Prolog terms. 132@see json_convert.pl converts between more natural Prolog terms and json 133terms. 134*/ 135 136%! http_client:http_convert_data(+In, +Fields, -Data, +Options) 137% 138% Hook implementation that supports reading JSON documents. It 139% processes the following option: 140% 141% * json_object(+As) 142% Where As is one of =term= or =dict=. If the value is =dict=, 143% json_read_dict/3 is used. 144 145http_client:http_convert_data(In, Fields, Data, Options) :- 146 memberchk(content_type(Type), Fields), 147 is_json_type(Type), 148 !, 149 ( memberchk(content_length(Bytes), Fields) 150 -> setup_call_cleanup( 151 ( stream_range_open(In, Range, [size(Bytes)]), 152 set_stream(Range, encoding(utf8)) 153 ), 154 json_read_to(Range, Data, Options), 155 close(Range)) 156 ; set_stream(In, encoding(utf8)), 157 json_read_to(In, Data, Options) 158 ). 159 160 161is_json_type(String) :- 162 http_parse_header_value(content_type, String, 163 media(Type, _Attributes)), 164 json_type(Type), 165 !. 166 167:- if(current_predicate(is_dict/1)). 168json_read_to(In, Data, Options) :- 169 memberchk(json_object(dict), Options), 170 !, 171 json_read_dict(In, Data, Options). 172:- endif. 173json_read_to(In, Data, Options) :- 174 json_read(In, Data, Options). 175 176%! json_type(?MediaType) is semidet. 177% 178% True if MediaType is a JSON media type. http_json:json_type/1 is 179% a multifile predicate and may be extended to facilitate 180% non-conforming clients. 181% 182% @arg MediaType is a term `Type`/`SubType`, where both `Type` and 183% `SubType` are atoms. 184 185json_type(application/jsonrequest). 186json_type(application/json). 187 188 189%! http:post_data_hook(+Data, +Out:stream, +HdrExtra) is semidet. 190% 191% Hook implementation that allows http_post_data/3 posting JSON 192% objects using one of the forms below. 193% 194% == 195% http_post(URL, json(Term), Reply, Options) 196% http_post(URL, json(Term, Options), Reply, Options) 197% == 198% 199% If Options are passed, these are handed to json_write/3. In 200% addition, this option is processed: 201% 202% * json_object(As) 203% If As is =dict=, json_write_dict/3 is used to write the 204% output. This is default if json(Dict) is passed. 205% 206% @tbd avoid creation of intermediate data using chunked output. 207 208:- if(current_predicate(is_dict/1)). 209http:post_data_hook(json(Dict), Out, HdrExtra) :- 210 is_dict(Dict), 211 !, 212 http:post_data_hook(json(Dict, [json_object(dict)]), 213 Out, HdrExtra). 214:- endif. 215http:post_data_hook(json(Term), Out, HdrExtra) :- 216 http:post_data_hook(json(Term, []), Out, HdrExtra). 217http:post_data_hook(json(Term, Options), Out, HdrExtra) :- 218 option(content_type(Type), HdrExtra, 'application/json'), 219 setup_call_cleanup( 220 ( new_memory_file(MemFile), 221 open_memory_file(MemFile, write, Handle) 222 ), 223 ( format(Handle, 'Content-type: ~w~n~n', [Type]), 224 json_write_to(Handle, Term, Options) 225 ), 226 close(Handle)), 227 setup_call_cleanup( 228 open_memory_file(MemFile, read, RdHandle, 229 [ free_on_close(true) 230 ]), 231 http_post_data(cgi_stream(RdHandle), Out, HdrExtra), 232 close(RdHandle)). 233 234:- if(current_predicate(is_dict/1)). 235json_write_to(Out, Term, Options) :- 236 memberchk(json_object(dict), Options), 237 !, 238 json_write_dict(Out, Term, Options). 239:- endif. 240json_write_to(Out, Term, Options) :- 241 json_write(Out, Term, Options). 242 243 244%! http_read_json(+Request, -JSON) is det. 245%! http_read_json(+Request, -JSON, +Options) is det. 246% 247% Extract JSON data posted to this HTTP request. Options are 248% passed to json_read/3. In addition, this option is processed: 249% 250% * json_object(+As) 251% One of =term= (default) to generate a classical Prolog 252% term or =dict= to exploit the SWI-Prolog version 7 data type 253% extensions. See json_read_dict/3. 254% 255% @error domain_error(mimetype, Found) if the mimetype is 256% not known (see json_type/1). 257% @error domain_error(method, Method) if the request is not 258% a =POST= or =PUT= request. 259 260http_read_json(Request, JSON) :- 261 http_read_json(Request, JSON, []). 262 263http_read_json(Request, JSON, Options) :- 264 select_option(content_type(Type), Options, Rest), 265 !, 266 delete(Request, content_type(_), Request2), 267 request_to_json([content_type(Type)|Request2], JSON, Rest). 268http_read_json(Request, JSON, Options) :- 269 request_to_json(Request, JSON, Options). 270 271request_to_json(Request, JSON, Options) :- 272 option(method(Method), Request), 273 option(content_type(Type), Request), 274 ( data_method(Method) 275 -> true 276 ; domain_error(method, Method) 277 ), 278 ( is_json_type(Type) 279 -> true 280 ; domain_error(mimetype, Type) 281 ), 282 http_read_data(Request, JSON, Options). 283 284data_method(post). 285data_method(put). 286data_method(patch). 287 288:- if(current_predicate(is_dict/1)). 289 290%! http_read_json_dict(+Request, -Dict) is det. 291%! http_read_json_dict(+Request, -Dict, +Options) is det. 292% 293% Similar to http_read_json/2,3, but by default uses the version 7 294% extended datatypes. 295 296http_read_json_dict(Request, Dict) :- 297 http_read_json_dict(Request, Dict, []). 298 299http_read_json_dict(Request, Dict, Options) :- 300 merge_options([json_object(dict)], Options, Options1), 301 http_read_json(Request, Dict, Options1). 302 303:- endif. 304 305%! reply_json(+JSONTerm) is det. 306%! reply_json(+JSONTerm, +Options) is det. 307% 308% Formulate a JSON HTTP reply. See json_write/2 for details. 309% The processed options are listed below. Remaining options are 310% forwarded to json_write/3. 311% 312% * content_type(+Type) 313% The default =|Content-type|= is =|application/json; 314% charset=UTF8|=. =|charset=UTF8|= should not be required 315% because JSON is defined to be UTF-8 encoded, but some 316% clients insist on it. 317% 318% * status(+Code) 319% The default status is 200. REST API functions may use 320% other values from the 2XX range, such as 201 (created). 321% 322% * json_object(+As) 323% One of =term= (classical json representation) or =dict= 324% to use the new dict representation. If omitted and Term 325% is a dict, =dict= is assumed. SWI-Prolog Version 7. 326 327:- if(current_predicate(is_dict/1)). 328reply_json(Dict) :- 329 is_dict(Dict), 330 !, 331 reply_json_dict(Dict). 332:- endif. 333reply_json(Term) :- 334 format('Content-type: application/json; charset=UTF-8~n~n'), 335 json_write(current_output, Term). 336 337:- if(current_predicate(is_dict/1)). 338reply_json(Dict, Options) :- 339 is_dict(Dict), 340 !, 341 reply_json_dict(Dict, Options). 342:- endif. 343reply_json(Term, Options) :- 344 reply_json2(Term, Options). 345 346%! reply_json_dict(+JSONTerm) is det. 347%! reply_json_dict(+JSONTerm, +Options) is det. 348% 349% As reply_json/1 and reply_json/2, but assumes the new dict based 350% data representation. Note that this is the default if the outer 351% object is a dict. This predicate is needed to serialize a list 352% of objects correctly and provides consistency with 353% http_read_json_dict/2 and friends. 354 355:- if(current_predicate(is_dict/1)). 356reply_json_dict(Dict) :- 357 format('Content-type: application/json; charset=UTF-8~n~n'), 358 json_write_dict(current_output, Dict). 359 360reply_json_dict(Dict, Options) :- 361 merge_options([json_object(dict)], Options, Options1), 362 reply_json2(Dict, Options1). 363:- endif. 364 365 366reply_json2(Term, Options) :- 367 select_option(content_type(Type), Options, Rest0, 'application/json'), 368 ( select_option(status(Code), Rest0, Rest) 369 -> format('Status: ~d~n', [Code]) 370 ; Rest = Rest0 371 ), 372 format('Content-type: ~w~n~n', [Type]), 373 json_write_to(current_output, Term, Rest).