/* Part of SWI-Prolog Author: Jan Wielemaker E-mail: J.Wielemaker@vu.nl WWW: http://www.swi-prolog.org Copyright (c) 2007-2018, University of Amsterdam VU University Amsterdam All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ :- 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 is_json_content_type/1 % +HeaderValue ]). :- use_module(library(http/http_client)). :- use_module(library(http/http_header)). :- use_module(library(http/http_stream)). :- use_module(library(http/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:post_data_hook/3, json_type/1. :- public 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 Most code doesn't need to use this directly; instead use library(http/http_server), which combines this library with the typical HTTP libraries that most servers need. This module adds hooks to several parts of the HTTP libraries, making them JSON-aware. Notably: - Make http_read_data/3 convert `application/json` and `application/jsonrequest` content to a JSON term. - Cause http_open/3 to accept post(json(Term)) to issue a POST request with JSON content. - Provide HTTP server and client utility predicates for reading and replying JSON: - http_read_json/2 - http_read_json/3 - http_read_json_dict/2 - http_read_json_dict/3 - reply_json/1 - reply_json/2 - reply_json_dict/1 - reply_json_dict/2 - Reply to exceptions in the server using an JSON document rather then HTML if the =|Accept|= header prefers application/json over text/html. 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_content_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_content_type(+ContentType) is semidet. % % True if ContentType is a header value (either parsed or as % atom/string) that denotes a JSON value. is_json_content_type(String) :- http_parse_header_value(content_type, String, media(Type, _Attributes)), json_type(Type), !. json_read_to(In, Data, Options) :- memberchk(json_object(dict), Options), !, json_read_dict(In, Data, Options). json_read_to(In, Data, Options) :- json_read(In, Data, Options). %! json_type(?MediaType) is semidet. % % True if MediaType is a JSON media type. http_json:json_type/1 is % a multifile predicate and may be extended to facilitate % non-conforming clients. % % @arg MediaType is a term `Type`/`SubType`, where both `Type` and % `SubType` are atoms. json_type(application/jsonrequest). json_type(application/json). %! http: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. http:post_data_hook(json(Dict), Out, HdrExtra) :- is_dict(Dict), !, http:post_data_hook(json(Dict, [json_object(dict)]), Out, HdrExtra). http:post_data_hook(json(Term), Out, HdrExtra) :- http:post_data_hook(json(Term, []), Out, HdrExtra). http: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)). json_write_to(Out, Term, Options) :- memberchk(json_object(dict), Options), !, json_write_dict(Out, Term, Options). 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 method is not % a =POST=, =PUT= or =PATCH=. 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_content_type(Type) -> true ; domain_error(mimetype, Type) ), http_read_data(Request, JSON, Options). data_method(post). data_method(put). data_method(patch). %! 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). %! 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. reply_json(Dict) :- is_dict(Dict), !, reply_json_dict(Dict). reply_json(Term) :- format('Content-type: application/json; charset=UTF-8~n~n'), json_write(current_output, Term). reply_json(Dict, Options) :- is_dict(Dict), !, reply_json_dict(Dict, Options). 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. 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). 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). /******************************* * STATUS HANDLING * *******************************/ :- multifile http:status_reply/3, http:serialize_reply/2. http:serialize_reply(json(Term), body(application/json, utf8, Content)) :- with_output_to(string(Content), json_write_dict(current_output, Term, [])). http:status_reply(Term, json(Reply), Options) :- prefer_json(Options.get(accept)), json_status_reply(Term, Lines, Extra), phrase(txt_message_lines(Lines), Codes), string_codes(Message, Codes), Reply = _{code:Options.code, message:Message}.put(Extra). txt_message_lines([]) --> []. txt_message_lines([nl|T]) --> !, "\n", txt_message_lines(T). txt_message_lines([flush]) --> !. txt_message_lines([FmtArgs|T]) --> dcg_format(FmtArgs), txt_message_lines(T). dcg_format(Fmt-Args, List, Tail) :- !, format(codes(List,Tail), Fmt, Args). dcg_format(ansi(_Style, Fmt,Args), List, Tail) :- !, format(codes(List,Tail), Fmt, Args). dcg_format(url(Pos), List, Tail) :- !, dcg_url(Pos, List, Tail). dcg_format(url(_URL, Label), List, Tail) :- !, format(codes(List,Tail), '~w', [Label]). dcg_format(Fmt, List, Tail) :- format(codes(List,Tail), Fmt, []). dcg_url(File:Line:Column, List, Tail) :- !, format(codes(List,Tail), '~w:~d:~d', [File, Line, Column]). dcg_url(File:Line, List, Tail) :- !, format(codes(List,Tail), '~w:~d', [File, Line]). dcg_url(File, List, Tail) :- !, format(codes(List,Tail), '~w', [File]). %! prefer_json(+Accept) % % True when the accept encoding prefers JSON. prefer_json(Accept) :- memberchk(media(application/json, _, JSONP, []), Accept), ( member(media(text/html, _, HTMLP, []), Accept) -> JSONP > HTMLP ; true ). %! json_status_reply(+Term, -MsgLines, -ExtraJSON) is semidet. json_status_reply(created(Location), [ 'Created: ~w'-[Location] ], _{location:Location}). json_status_reply(moved(Location), [ 'Moved to: ~w'-[Location] ], _{location:Location}). json_status_reply(moved_temporary(Location), [ 'Moved temporary to: ~w'-[Location] ], _{location:Location}). json_status_reply(see_other(Location), [ 'See: ~w'-[Location] ], _{location:Location}). json_status_reply(bad_request(ErrorTerm), Lines, _{}) :- '$messages':translate_message(ErrorTerm, Lines, []). json_status_reply(authorise(Method), [ 'Authorization (~p) required'-[Method] ], _{}). json_status_reply(forbidden(Location), [ 'You have no permission to access: ~w'-[Location] ], _{location:Location}). json_status_reply(not_found(Location), [ 'Path not found: ~w'-[Location] ], _{location:Location}). json_status_reply(method_not_allowed(Method,Location), [ 'Method not allowed: ~w'-[UMethod] ], _{location:Location, method:UMethod}) :- upcase_atom(Method, UMethod). json_status_reply(not_acceptable(Why), [ 'Request is not acceptable: ~p'-[Why] ], _{}). json_status_reply(server_error(ErrorTerm), Lines, _{}) :- '$messages':translate_message(ErrorTerm, Lines, []). json_status_reply(service_unavailable(Why), [ 'Service unavailable: ~p'-[Why] ], _{}).