1JSON::Create(3) User Contributed Perl Documentation JSON::Create(3)
2
6 JSON::Create - Create JSON
7
9 use JSON::Create 'create_json';
10 my %hash = (a => 'b', c => 'd');
11 print create_json (\%hash);
12 produces output
14 {"c":"d","a":"b"}
16 (This example is included as examples/synopsis.pl
18 <https://fastapi.metacpan.org/source/BKB/JSON-
19 Create-0.35/examples/synopsis.pl> in the distribution.)
20
22 This document describes JSON::Create version 0.35, corresponding to git
23 commit ffe5ce4b3304dac8f668133563a276f831966bbe
24 <https://github.com/benkasminbullock/json-
25 create/commit/ffe5ce4b3304dac8f668133563a276f831966bbe> at Fri Jul 16
26 07:42:12 2021 +0900.
27
29 JSON::Create encodes Perl variables into JSON. The basic routine
30 "create_json" gives common defaults. The stricter version
31 "create_json_strict" accepts only unambiguous inputs. For more
32 customization, an object created with "new" and run with "create"
33 allows specifying behaviour in more detail.
34 JSON::Create handles no string encoding except UTF-8. It supports
36 serialization of objects via user-defined callbacks. Its companion
37 module JSON::Parse parses JSON into Perl.
38 Errors in processing result in a warning and an undefined return value.
40 This behaviour can be altered with the method "fatal_errors".
41
43 create_json
44 my $json = create_json (\%hash, %args);
45 This converts a hash reference, array reference, or scalar into JSON.
47 The return value is the output JSON as a string. The arguments
48 available in %args are the same as "new" and "set".
49 Details of the conversion of each type are given in "CONVERSIONS".
51 create_json_strict
53 my $json = create_json_strict (\%hash, %args);
54 This is the same as "create_json", except that it rejects ambiguous
56 inputs. See "strict" for details. It is effectively identical to
57 my $json = create_json (\%hash, %args, strict => 1);
59 The "strict" option can be set in %args without producing an error, but
61 it will be overridden.
62 This function was added in version 0.20 of the module.
64 write_json
66 write_json ('file.json', \%hash, %options);
67 Write the contents of %hash (or an array reference or scalar) to the
69 file specified in the first argument. This takes all the same arguments
70 as "create_json", "new" and "set".
71 This function was added in version 0.30 of the module.
73
75 If you need to alter the format of the output from the defaults of
76 "create_json" or "create_json_strict", create an object with "new" and
77 then set preferences on that object before producing output with
78 "create".
79 create
81 my $json = $jc->create ($input);
82 This does exactly the same thing as "create_json", unless the output
84 format associated with $jc has been altered using "Methods for
85 formatting the output". The return value is the output JSON.
86 fatal_errors
88 $jc->fatal_errors (1);
89 If this is called with a true value, errors in the input are upgraded
91 from warnings to fatal errors.
92 use JSON::Create;
94 my $jc = JSON::Create->new ();
95 $jc->fatal_errors (1);
96 my $invalid_utf8 = "\x{99}\x{ff}\x{88}";
97 eval {
98 $jc->run ($invalid_utf8);
99 };
100 if ($@) {
101 print "Fatal error: $@\n";
102 }
103 produces output
105 Fatal error: Invalid UTF-8 at /usr/home/ben/projects/json-create/examples/fatal-errors.pl line 9.
107 (This example is included as examples/fatal-errors.pl
109 <https://fastapi.metacpan.org/source/BKB/JSON-
110 Create-0.35/examples/fatal-errors.pl> in the distribution.)
111 This method was added in version 0.10 of the module.
113 new
115 my $jc = JSON::Create->new ();
116 Create a new "JSON::Create" object. Use "create" to generate JSON with
118 it. It is possible to supply arguments with new:
119 my $jc = JSON::Create->new (%args);
121 All of the same values as "set" may be used.
123 set
125 $json->set (strict => 1, fatal_errors => 1, validate => 1);
126 downgrade_utf8 option
128 This corresponds to "downgrade_utf8".
129 escape_slash option
131 This corresponds to "escape_slash".
132 fatal_errors option
134 This corresponds to "fatal_errors".
135 indent option
137 This corresponds to "indent".
138 no_javascript_safe option
140 This corresponds to "no_javascript_safe".
141 non_finite_handler option
143 This corresponds to "non_finite_handler".
144 object_handler option
146 This corresponds to "object_handler".
147 replace_bad_utf8 option
149 This corresponds to "replace_bad_utf8".
150 sort option
152 This corresponds to "sort".
153 strict option
155 This corresponds to "strict".
156 type_handler option
158 This corresponds to "type_handler".
159 unicode_escape_all option
161 This corresponds to "unicode_escape_all".
162 unicode_upper option
164 This corresponds to "unicode_upper".
165 validate option
167 This corresponds to "validate".
168 strict
170 $jc->strict (1);
171 This switches on rejection of ambiguous inputs, which means
173 β’ all non-data types, including objects,
175 β’ strings containing non-ASCII bytes (bytes with values of from 128
177 to 255) which are not marked as "utf8" (character strings),
178 β’ non-finite floating point numbers (NaN or infinite values), and
180 β’ scalar references.
182 Calling "create" with such inputs results in a return value of "undef"
184 (the undefined value) and a warning being printed. You can override the
185 behaviour for objects with "obj", "obj_handler", for non-data types and
186 scalar references with "type_handler", and for non-finite numbers with
187 "non_finite_handler".
188 The rejection of non-ASCII bytes in non-"utf8" strings cannot be
190 overridden, so users need to ensure that all input is either ASCII-only
191 or character string-only ("utf8").
192 This method was added in version 0.20 of the module.
194
196 These methods work on the object created with "new" to format the
197 output JSON in a different way from the default when operating
198 "create".
199 These methods do not affect the behaviour of "create_json" or
201 "create_json_strict".
202 bool
204 $jc->bool ('boolean');
205 $jc->bool (qw/boolean JSON::Tiny::_Bool/);
206 Given a list of names of object types, the JSON::Create object, $jc in
208 the example, will convert objects of these types into the JSON literals
209 "true" or "false" depending on whether Perl thinks they're true or
210 false.
211 Converting booleans to "true" and "false"
213 use JSON::Create;
215 use boolean;
216 my $thing = {'Yes' => true, 'No' => false};
217 my $jc = JSON::Create->new ();
218 print $jc->run ($thing), "\n";
219 $jc->bool ('boolean');
220 print $jc->run ($thing), "\n";
221 produces output
223 {"Yes":1,"No":0}
225 {"Yes":true,"No":false}
226 (This example is included as examples/boolean.pl
228 <https://fastapi.metacpan.org/source/BKB/JSON-
229 Create-0.35/examples/boolean.pl> in the distribution.)
230 If you prefer to take over all object handling yourself, there is also
232 "obj_handler", which overrides what is set with "bool".
233 Interoperability
235 The boolean values of the following Perl modules can interoperate with
237 JSON::Create.
238 boolean
240 $jc->bool ('boolean');
241 JSON::Tiny
243 $jc->bool ('JSON::Tiny::_Bool');
244 Round trip compatibility is also confirmed for JSON::Tiny version
246 0.54.
247 JSON::PP
249 $jc->bool ('JSON::PP::Boolean');
250 Round trip compatibility is also confirmed for JSON::PP version
252 2.27300.
253 Types::Serialiser
255 $jc->bool ('JSON::PP::Boolean');
256 Please note the above is not a typo, JSON::PP::Boolean is the
258 correct object type for Types::Serialiser. To confirm this, try
259 print ref $Types::Serialiser::false;
261 Mojo::JSON
263 $jc->bool ('JSON::PP::Boolean', 'Mojo::JSON::_Bool');
264 Round trip compatibility is also confirmed for Mojo::JSON version
266 8.65.
267 The current version of Mojo::JSON (Mojolicious version 8.65) uses
269 "JSON::PP::Boolean" for true and false values. Older versions used
270 their own type, "Mojo::JSON::_Bool".
271 JSON::Create's compatibility tests for Mojo::JSON compatibility are
273 available only in the git repository as xt/mojo-json.t, rather than
274 in the CPAN release, because different versions of Mojolicious
275 differ a lot in not only function names but also variable names, as
276 seen above.
277 You can handle multiple modules with the same object:
279 $jc->bool (qw/boolean JSON::Tiny::_Bool JSON::PP::Boolean/);
281 The compatibility of the above modules can be confirmed by running the
283 test script t/bool.t in the distribution. However, JSON::Create does
284 not install these modules, so unless you have installed them yourself,
285 the tests will just be skipped.
286 More modules will be added to this list as time permits.
288 cmp
290 Set a user-defined routine to be used with the "sort" option.
291 Sorting the keys of objects in a user-defined order will reduce the
293 performance of the module. The built-in variables $a and $b are not
294 available to your sort routine, so you need to get the arguments
295 yourself.
296 Sorting object elements case-independently
298 use utf8;
300 use FindBin '$Bin';
301 use JSON::Create;
302 my $jc = JSON::Create->new (sort => 1, indent => 1);
303 $jc->cmp (\&uccmp);
304 my %emojis = (
305 lifeforms => {
306 Kingkong => 'π¦',
307 goat => 'π',
308 elephant => 'π',
309 Grape => 'π',
310 Watermelon => 'π',
311 melon => 'π',
312 # What if life exists based on another element? π
313 siliconbased => 'β',
314 },
315 );
316 print $jc->run (\%emojis);
317 sub uccmp
319 {
320 my ($a, $b) = @_;
321 return uc ($a) cmp uc ($b);
322 }
323 produces output
325 {
327 "lifeforms":{
328 "elephant":"π",
329 "goat":"π",
330 "Grape":"π",
331 "Kingkong":"π¦",
332 "melon":"π",
333 "siliconbased":"β",
334 "Watermelon":"π"
335 }
336 }
337 (This example is included as examples/cmp.pl
339 <https://fastapi.metacpan.org/source/BKB/JSON-
340 Create-0.35/examples/cmp.pl> in the distribution.)
341 This method was added in version 0.29 of the module.
343 downgrade_utf8
345 $jc->downgrade_utf8 (1);
346 If this is set to a true value, the return value of "create_json" or
348 "create" is never upgraded to character strings, or "utf8". This
349 overrides the default behaviour, which is to upgrade the output to
350 "utf8" if any part of the input is "utf8", or if the user has requested
351 replacement with "replace_bad_utf8" and there are bad characters in the
352 user's input. See "UNICODE HANDLING" for details. All output of
353 JSON::Create is valid UTF-8, regardless of what this flag is set to.
354 See "Output is valid UTF-8".
355 This method was added in version 0.18 of the module.
357 escape_slash
359 $jc->escape_slash (1);
360 Call this with a true value to make the slash (known as the "solidus"
362 in the JSON specification) be escaped with a backslash, so "/" gets
363 turned into "\/". Call this with any false value to make the slash not
364 be escaped (the default behaviour).
365 Escaping slashes
367 use JSON::Create;
369 my $jc = JSON::Create->new ();
370 my $in = {'/dog/' => '/run/'};
371 print $jc->run ($in), "\n";
372 $jc->escape_slash (1);
373 print $jc->run ($in), "\n";
374 $jc->escape_slash (0);
375 print $jc->run ($in), "\n";
376 produces output
378 {"/dog/":"/run/"}
380 {"\/dog\/":"\/run\/"}
381 {"/dog/":"/run/"}
382 (This example is included as examples/escape-slash.pl
384 <https://fastapi.metacpan.org/source/BKB/JSON-
385 Create-0.35/examples/escape-slash.pl> in the distribution.)
386 See also "Other escapes".
388 This method was added in version 0.07 of the module.
390 indent
392 $jc->indent (1);
393 Add whitespace indentation to the output. The formula applied is to add
395 a newline plus indentation after each opening bracket, add the same
396 after each comma, and add the same before each closing bracket. Tabs
397 are used for all indentation. The number of tabs is decided by the
398 number of brackets open.
399 Example of indentation
401 use JSON::Create;
403 my %thing = ("it's your thing" => [qw! do what you !, {wanna => 'do'}],
404 "I can't tell you" => [{who => 2}, qw! sock it!, 2]);
405 my $jc = JSON::Create->new ();
406 $jc->indent (1);
407 print $jc->run (\%thing);
408 produces output
410 {
412 "it's your thing":[
413 "do",
414 "what",
415 "you",
416 {
417 "wanna":"do"
418 }
419 ],
420 "I can't tell you":[
421 {
422 "who":2
423 },
424 "sock",
425 "it",
426 2
427 ]
428 }
429 (This example is included as examples/indent.pl
431 <https://fastapi.metacpan.org/source/BKB/JSON-
432 Create-0.35/examples/indent.pl> in the distribution.)
433 Reformatting the indentation
435 Users who prefer a different style of indentation should easily be able
437 to modify this output to their needs using simple substitutions, for
438 example "s/^(\t+)/ " " x length ($1) /gesm;" will convert from tabs to
439 two space indentation.
440 use JSON::Create;
442 my %thing = ("it's your thing" => [qw! do what you !, {wanna => 'do'}],
443 "I can't tell you" => [{who => 2}, qw! sock it!, 2]);
444 my $jc = JSON::Create->new ();
445 $jc->indent (1);
446 my $out = $jc->run (\%thing);
447 $out =~ s/^(\t+)/ " " x length ($1) /gesm;
448 print $out;
449 produces output
451 {
453 "I can't tell you":[
454 {
455 "who":2
456 },
457 "sock",
458 "it",
459 2
460 ],
461 "it's your thing":[
462 "do",
463 "what",
464 "you",
465 {
466 "wanna":"do"
467 }
468 ]
469 }
470 (This example is included as examples/indent-format.pl
472 <https://fastapi.metacpan.org/source/BKB/JSON-
473 Create-0.35/examples/indent-format.pl> in the distribution.)
474 This method was added in version 0.27 of the module.
476 no_javascript_safe
478 $jc->no_javascript_safe (1);
479 If called with a true value, this switches off JavaScript protection in
481 the output JSON. If called with a false value, the JavaScript
482 protection is switched on again.
483 Switching JavaScript-safety on and off
485 use JSON::Create;
487 my $in = ["\x{2028}"];
488 my $jc = JSON::Create->new ();
489 print $jc->run ($in), "\n";
490 $jc->no_javascript_safe (1);
491 print $jc->run ($in), "\n";
492 produces output
494 ["\u2028"]
496 ["β¨"]
497 (This example is included as examples/js-safe.pl
499 <https://fastapi.metacpan.org/source/BKB/JSON-Create-0.35/examples/js-
500 safe.pl> in the distribution.)
501 See also "U+2028 and U+2029 (JavaScript clashes)".
503 non_finite_handler
505 $jc->non_finite_handler (\& handler);
506 This overrides the default behaviour for handling non-finite floating
508 point numbers, in other words NaN (not a number) and negative or
509 positive infinity, with a user-defined routine. The default behaviour
510 of this module is described at "Floating point numbers".
511 The routine "handler" is supplied with the non-finite number as its
513 sole argument, and returns one argument, the output JSON.
514 Using null for infinity and NaN
516 To always use "null" in place of the default, supply a function like
518 the following:
519 use JSON::Create;
521 my $bread = { 'curry' => -sin(9**9**9) };
522 my $jcnfh = JSON::Create->new ();
523 print $jcnfh->run ($bread), "\n";
524 $jcnfh->non_finite_handler(sub { return 'null'; });
525 print $jcnfh->run ($bread), "\n";
526 produces output
528 {"curry":"nan"}
530 {"curry":null}
531 (This example is included as examples/non-finite-handler.pl
533 <https://fastapi.metacpan.org/source/BKB/JSON-Create-0.35/examples/non-
534 finite-handler.pl> in the distribution.)
535 β’ Calling convention
537 The non_finite_handler routine is passed a single argument and is
539 expected to return a single argument, the JSON to output. It is
540 called in scalar context. In other words, the call looks like the
541 following:
542 $json = &{$jc->{non_finite_handler}} ($item);
544 To pass or return multiple values via the "non_finite_handler"
546 callback, use a closure. See the discussion at "obj" for an
547 example.
548 β’ Returning undef halts processing
550 If your handler returns the undefined value, "create" prints a
552 warning "Undefined value from user routine", halts further
553 processing of the input, and returns the undefined value.
554 β’ Delete the handler with any false value
556 To remove the handler, simply call the function without an
558 argument,
559 $jc->non_finite_handler ();
561 or with a false argument:
563 $jc->non_finite_handler (0);
565 The behaviour then reverts to the default.
567 β’ Checking the output JSON
569 The JSON output by your handler may be checked for validity by
571 switching on validation using "validate". If you do not use this,
572 and your return value happens to contain invalid UTF-8, you may see
573 the error "Invalid UTF-8 from user routine". Please see "UTF-8
574 validation of user-supplied JSON" for more about this error.
575 β’ Exception handling
577 Exceptions ("die") thrown within "non_finite_handler" callbacks are
579 not caught by "create" but passed through to the parent. Please see
580 the discussion at "obj" for an example.
581 This method was added in version 0.17 of the module.
583 obj
585 $jc->obj ('Zilog::Z80' => sub { my ($obj) = @_; print "\"Z80\""; });
586 Register JSON generators for Perl objects. When JSON::Create finds an
588 object with a registered type, it will call the method you have
589 supplied.
590 The argument to "obj" is a hash. The keys are object names, and the
592 corresponding values are code references to the JSON serializer for
593 that object:
594 $jc->obj (
596 'My::Object' => \& object_to_json,
597 );
598 The output is passed through to the output string unaltered. To have
600 your JSON output checked for validity, use the "validate" option.
601 The function is called with the object reference as its only argument,
603 as if called like this:
604 my $user_json = $my_object->object_to_json ();
606 The return value of the function, "object_to_json" in the above
608 example, must be a single value, a string containing the object's JSON
609 encoding.
610 use JSON::Create;
612 my $jc = JSON::Create->new ();
613 package Zilog::Z80;
614 sub new { return bless { memory => '64 kbytes' }; }
615 sub to_json {
616 my ($self) = @_;
617 return '"I can address as many as '.$self->{memory}.' of memory"';
618 }
619 1;
620 package main;
621 my $zilog = Zilog::Z80->new ();
622 my %stuff = (zilog => $zilog);
623 print $jc->run (\%stuff), "\n";
624 # Set up our object's method for printing JSON.
625 $jc->obj (
626 'Zilog::Z80' => \& Zilog::Z80::to_json,
627 );
628 print $jc->run (\%stuff), "\n";
629 produces output
631 {"zilog":{"memory":"64 kbytes"}}
633 {"zilog":"I can address as many as 64 kbytes of memory"}
634 (This example is included as examples/zilog.pl
636 <https://fastapi.metacpan.org/source/BKB/JSON-
637 Create-0.35/examples/zilog.pl> in the distribution.)
638 The function is called "in scalar context", so
640 use JSON::Create;
642 my $jc = JSON::Create->new ();
643 $jc->validate (1);
644 $jc->type_handler (sub {
645 return ('"a"', '"b"', '"c"');
646 });
647 print $jc->run ({ x => *STDOUT });
648 produces output
650 {"x":"c"}
652 (This example is included as examples/too-many-values.pl
654 <https://fastapi.metacpan.org/source/BKB/JSON-Create-0.35/examples/too-
655 many-values.pl> in the distribution.)
656 If you need to pass or return more than a single argument, use a
658 closure:
659 use JSON::Create;
661 package My::Cool::Object;
662 sub new { return bless {}; }
663 sub serialize { return ('true', 'false'); };
664 1;
665 package main;
666 my $object = My::Cool::Object->new ();
667 my $jc = JSON::Create->new ();
668 my ($arg1, $arg2);
669 $jc->obj (
670 'My::Cool::Object' => sub {
671 my ($obj) = @_;
672 my ($value1, $value2) = My::Cool::Object::serialize ($obj, $arg1, $arg2);
673 return $value2;
674 },
675 );
676 print $jc->run ({cool => $object});
677 produces output
679 {"cool":false}
681 (This example is included as examples/closure.pl
683 <https://fastapi.metacpan.org/source/BKB/JSON-
684 Create-0.35/examples/closure.pl> in the distribution.)
685 Throwing an exception in your callback
687 Exceptions (fatal errors) are not caught by JSON::Create, so if you
689 want to halt the execution of JSON::Create, you can throw an exception
690 within your callback.
691 use JSON::Create;
693 package Funky::Monkey::Baby; sub new {return bless {};} 1;
694 package main;
695 my $jc = JSON::Create->new ();
696 $jc->obj (
697 'Funky::Monkey::Baby' => sub {
698 die "There is no such thing as a funky monkey baby";
699 },
700 );
701 eval {
702 $jc->run ({fmb => Funky::Monkey::Baby->new ()});
703 };
704 if ($@) {
705 print "$@\n";
706 }
707 produces output
709 There is no such thing as a funky monkey baby at /usr/home/ben/projects/json-create/examples/exception.pl line 10.
711 (This example is included as examples/exception.pl
713 <https://fastapi.metacpan.org/source/BKB/JSON-
714 Create-0.35/examples/exception.pl> in the distribution.)
715 If you prefer to take over all object handling yourself, there is also
717 "obj_handler".
718 If your handler returns the undefined value, "create" prints a warning
720 "Undefined value from user routine", halts further processing of the
721 input, and returns the undefined value.
722 obj_handler
724 $jc->obj_handler (\& my_obj_handler);
725 Supply an object handler. If you supply this, all objects will be
727 handled by your handler. For example, you can replace all objects with
728 'null' or die if an object is found.
729 β’ Calling convention
731 The obj_handler routine is passed a single argument and is expected
733 to return a single argument, the JSON to output. It is called in
734 scalar context. In other words, the call looks like the following:
735 $json = &{$jc->{obj_handler}} ($item);
737 To pass or return multiple values via the "obj_handler" callback,
739 use a closure. See the discussion at "obj" for an example.
740 β’ Returning undef halts processing
742 If your handler returns the undefined value, "create" prints a
744 warning "Undefined value from user routine", halts further
745 processing of the input, and returns the undefined value.
746 β’ Delete the handler with any false value
748 To remove the handler, simply call the function without an
750 argument,
751 $jc->obj_handler ();
753 or with a false argument:
755 $jc->obj_handler (0);
757 The behaviour then reverts to the default.
759 β’ Checking the output JSON
761 The JSON output by your handler may be checked for validity by
763 switching on validation using "validate". If you do not use this,
764 and your return value happens to contain invalid UTF-8, you may see
765 the error "Invalid UTF-8 from user routine". Please see "UTF-8
766 validation of user-supplied JSON" for more about this error.
767 β’ Exception handling
769 Exceptions ("die") thrown within "obj_handler" callbacks are not
771 caught by "create" but passed through to the parent. Please see the
772 discussion at "obj" for an example.
773 Turning various types of object into JSON
775 Here is an example of handling various types of object with a user-
777 supplied handler:
778 use utf8;
780 use FindBin '$Bin';
781 use JSON::Create;
782 package Monkey::Shines;
783 sub new { return bless {}; }
784 1;
785 package Monkey::Shines::Bool;
786 sub true { my $monkey = 1; return bless \$monkey; }
787 sub false { my $monkey = 0; return bless \$monkey; }
788 1;
789 package main;
790 my $monkeys = {
791 CuriousGeorge => Monkey::Shines->new (),
792 KingKong => Monkey::Shines::Bool->true (),
793 FunkyKong => Monkey::Shines::Bool->false (),
794 PeterTork => "Monkees",
795 };
796 my $obj_handler = sub {
797 my ($obj) = @_;
798 if (ref ($obj) =~ /bool/i) {
799 return $$obj ? 'true' : 'false';
800 }
801 else {
802 return 'null';
803 }
804 };
805 my $jc = JSON::Create->new (indent => 1, sort => 1);
806 print $jc->run ($monkeys), "\n";
807 $jc->obj_handler ($obj_handler);
808 print $jc->run ($monkeys), "\n";
809 $jc->obj_handler ();
810 print $jc->run ($monkeys), "\n";
811 produces output
813 {
815 "CuriousGeorge":{},
816 "FunkyKong":0,
817 "KingKong":1,
818 "PeterTork":"Monkees"
819 }
820 {
822 "CuriousGeorge":null,
823 "FunkyKong":false,
824 "KingKong":true,
825 "PeterTork":"Monkees"
826 }
827 {
829 "CuriousGeorge":{},
830 "FunkyKong":0,
831 "KingKong":1,
832 "PeterTork":"Monkees"
833 }
834 (This example is included as examples/obj-handler.pl
836 <https://fastapi.metacpan.org/source/BKB/JSON-Create-0.35/examples/obj-
837 handler.pl> in the distribution.)
838 Turning everything into JSON
840 Here is an example of a "try harder" routine which does something like
842 the JSON module does, by looking for methods on all objects:
843 use utf8;
845 use FindBin '$Bin';
846 use JSON::Create 'create_json';
847 use Mojo::URL;
848 use Path::Tiny;
849 sub try_harder
851 {
852 my ($obj) = @_;
853 my $type = ref $obj;
854 if ($obj->can ('TO_JSON')) {
855 print "Jsonifying $type with 'TO_JSON'.\n";
856 return create_json ($obj->TO_JSON ());
857 }
858 elsif ($obj->can ('to_string')) {
859 print "Stringifying $type with 'to_string'.\n";
860 # The call to "create_json" makes sure that the string is
861 # valid as a JSON string.
862 return create_json ($obj->to_string ());
863 }
864 else {
865 return create_json ($obj);
866 }
867 }
868 my $jc = JSON::Create->new (indent => 1, sort => 1, validate => 1);
870 $jc->obj_handler (\& try_harder);
871 print $jc->run ({
872 url => Mojo::URL->new('http://sri:foo@example.com:3000/foo?foo=bar#23'),
873 path => path ('/home/ben/software/install/bin/perl'),
874 }), "\n";
875 produces output
877 Jsonifying Path::Tiny with 'TO_JSON'.
879 Stringifying Mojo::URL with 'to_string'.
880 {
881 "path":"/home/ben/software/install/bin/perl",
882 "url":"http://example.com:3000/foo?foo=bar#23"
883 }
884 (This example is included as examples/try-harder.pl
886 <https://fastapi.metacpan.org/source/BKB/JSON-Create-0.35/examples/try-
887 harder.pl> in the distribution.)
888 This "obj_handler" overrides whatever you have set with "bool" or
890 "obj". Currently, it does not print a warning about this. See "BUGS".
891 The routine you use to handle objects may be the same as the routine
892 you use to handle types. See "type_handler". For more details about the
893 callbacks, see "obj".
894 This method was added in version 0.13 of the module.
896 replace_bad_utf8
898 $jc->replace_bad_utf8 (1);
899 Replace invalid UTF-8 in the inputs with the Unicode replacement
901 character U+FFFD, rather than produce the warning or error "Invalid
902 UTF-8".
903 If "replace_bad_utf8" is used on input containing only strings not
905 marked as character strings, and bad UTF-8 is found, JSON::Create marks
906 the output as a character string. Otherwise the replacement character
907 itself is just a series of broken bytes. This behaviour can be altered
908 with the method "downgrade_utf8".
909 This method was added in version 0.12 of the module.
911 set_fformat
913 $jc->set_fformat ('%e');
914 This sets the printf-style format string used to print floating point
916 numbers. This is validated and a warning printed if the format cannot
917 be used. The format is also restricted to a maximum length to prevent
918 buffer overflows within the module.
919 Setting the format of floating point numbers
921 use JSON::Create;
923 my $jc = JSON::Create->new ();
924 my @array = (1000000000.0,3.141592653589793238462643383279502884197169399375105820974944592307816406,0.000000001);
925 print $jc->run (\@array), "\n";
926 $jc->set_fformat ('%.3f');
927 print $jc->run (\@array), "\n";
928 $jc->set_fformat ('%E');
929 print $jc->run (\@array), "\n";
930 $jc->set_fformat ();
931 print $jc->run (\@array), "\n";
932 produces output
934 [1e+09,3.14159,1e-09]
936 [1000000000.000,3.142,0.000]
937 [1.000000E+09,3.141593E+00,1.000000E-09]
938 [1e+09,3.14159,1e-09]
939 (This example is included as examples/set-fformat.pl
941 <https://fastapi.metacpan.org/source/BKB/JSON-Create-0.35/examples/set-
942 fformat.pl> in the distribution.)
943 This method was added in version 0.07 of the module.
945 sort
947 $jc->sort (1);
948 Sort hash keys. The default is to use Perl's string sorting. Use "cmp"
950 to supply your own sorting routine. This does not affect the order of
951 array elements, only hash keys.
952 JSON with indentation and sorted keys
954 use utf8;
956 use JSON::Create;
957 my %emojis = (
959 animals => {
960 kingkong => 'π¦',
961 goat => 'π',
962 elephant => 'π',
963 },
964 fruit => {
965 grape => 'π',
966 watermelon => 'π',
967 melon => 'π',
968 },
969 baka => { # Japanese words
970 'γ°' => 'γ',
971 'γ' => 'γ»',
972 'γΎ' => 'γ¬γ',
973 },
974 );
975 my $jc = JSON::Create->new ();
976 my @moons = qw!π π π π π π π π!;
978 my $i = 0;
979 for (@moons) {
980 $emojis{moons}{$_} = $i;
981 $i++;
982 }
983 $jc->sort (1);
985 $jc->indent (1);
986 print $jc->run (\%emojis);
987 produces output
989 {
991 "animals":{
992 "elephant":"π",
993 "goat":"π",
994 "kingkong":"π¦"
995 },
996 "baka":{
997 "γ":"γ»",
998 "γ°":"γ",
999 "γΎ":"γ¬γ"
1000 },
1001 "fruit":{
1002 "grape":"π",
1003 "melon":"π",
1004 "watermelon":"π"
1005 },
1006 "moons":{
1007 "π":0,
1008 "π":1,
1009 "π":2,
1010 "π":3,
1011 "π":4,
1012 "π":5,
1013 "π":6,
1014 "π":7
1015 }
1016 }
1017 (This example is included as examples/sort.pl
1019 <https://fastapi.metacpan.org/source/BKB/JSON-
1020 Create-0.35/examples/sort.pl> in the distribution.)
1021 This method was added in version 0.29 of the module.
1023 type_handler
1025 $jc->type_handler (sub {return 'null'});
1026 By default, when JSON::Create encounters a variable of a type which it
1028 doesn't know what to do with, such as a glob or code reference, it
1029 prints a warning and returns an undefined value. See "Code, regexes,
1030 and other references". The method "type_handler" sets up a callback
1031 which is called when a variable of an unhandled type is found in the
1032 input. For example, to put the JSON literal "null" in the output when a
1033 reference to a variable of an unhandled type is encountered, rather
1034 than print an error, the above example will do it.
1035 β’ Calling convention
1037 The type_handler routine is passed a single argument and is
1039 expected to return a single argument, the JSON to output. It is
1040 called in scalar context. In other words, the call looks like the
1041 following:
1042 $json = &{$jc->{type_handler}} ($item);
1044 To pass or return multiple values via the "type_handler" callback,
1046 use a closure. See the discussion at "obj" for an example.
1047 β’ Returning undef halts processing
1049 If your handler returns the undefined value, "create" prints a
1051 warning "Undefined value from user routine", halts further
1052 processing of the input, and returns the undefined value.
1053 β’ Delete the handler with any false value
1055 To remove the handler, simply call the function without an
1057 argument,
1058 $jc->type_handler ();
1060 or with a false argument:
1062 $jc->type_handler (0);
1064 The behaviour then reverts to the default.
1066 β’ Checking the output JSON
1068 The JSON output by your handler may be checked for validity by
1070 switching on validation using "validate". If you do not use this,
1071 and your return value happens to contain invalid UTF-8, you may see
1072 the error "Invalid UTF-8 from user routine". Please see "UTF-8
1073 validation of user-supplied JSON" for more about this error.
1074 β’ Exception handling
1076 Exceptions ("die") thrown within "type_handler" callbacks are not
1078 caught by "create" but passed through to the parent. Please see the
1079 discussion at "obj" for an example.
1080 Ways to handle types
1082 The following example shows a few possibilities for handling types:
1084 use utf8;
1086 use FindBin '$Bin';
1087 use JSON::Create 'create_json';
1088 my %crazyhash = (
1089 'code' => sub { return "κ°λ¨μ€νμΌ"; },
1090 'regex' => qr/.*/,
1091 'glob' => *STDOUT,
1092 );
1093 # Let's validate the output of the subroutine below.
1094 my $jc = JSON::Create->new (validate => 1, indent => 1, sort => 1);
1095 # Try this one weird old trick to convert your Perl type.
1096 $jc->type_handler (
1097 sub {
1098 my ($thing) = @_;
1099 my $value;
1100 my $type = ref ($thing);
1101 if ($type eq 'CODE') {
1102 $value = &$thing;
1103 }
1104 else {
1105 $value = "$thing";
1106 }
1107 return create_json ({ type => $type, value => $value, },
1108 indent => 1, sort => 1);
1109 }
1110 );
1111 print $jc->run (\%crazyhash), "\n";
1112 produces output
1114 {
1116 "code":{
1117 "type":"CODE",
1118 "value":"κ°λ¨μ€νμΌ"
1119 },
1120 "glob":{
1121 "type":"GLOB",
1122 "value":"GLOB(0x209a82a0)"
1123 },
1124 "regex":{
1125 "type":"Regexp",
1126 "value":"(?^:.*)"
1127 }
1128 }
1129 (This example is included as examples/type-handler.pl
1131 <https://fastapi.metacpan.org/source/BKB/JSON-
1132 Create-0.35/examples/type-handler.pl> in the distribution.)
1133 If the "strict" option is chosen, this method is also passed scalar
1135 references.
1136 use JSON::Create;
1138 my $jc = JSON::Create->new ();
1139 $jc->strict (1);
1140 print "Before: ", $jc->run (\1), "\n";
1141 $jc->type_handler (sub {
1142 my ($thing) = @_;
1143 if (ref $thing eq 'SCALAR') {
1144 return $$thing;
1145 }
1146 });
1147 print "After: ", $jc->run (\1), "\n";
1148 produces output
1150 Input's type cannot be serialized to JSON at /usr/home/ben/projects/json-create/examples/type-handler-scalar.pl line 7.
1152 Use of uninitialized value in print at /usr/home/ben/projects/json-create/examples/type-handler-scalar.pl line 7.
1153 Before:
1154 After: 1
1155 (This example is included as examples/type-handler-scalar.pl
1157 <https://fastapi.metacpan.org/source/BKB/JSON-
1158 Create-0.35/examples/type-handler-scalar.pl> in the distribution.)
1159 This method was added in version 0.10 of the module.
1161 unicode_escape_all
1163 $jc->unicode_escape_all (1);
1164 Call this with a true value to make all Unicode characters be escaped
1166 into the "\u3000" format. A false value switches that off again.
1167 Escape all Unicode
1169 use JSON::Create;
1171 use utf8;
1172 my $jc = JSON::Create->new ();
1173 my $in = 'θ΅€γΓΆοΌ‘βΟͺ';
1174 print $jc->run ($in), "\n";
1175 $jc->unicode_escape_all (1);
1176 print $jc->run ($in), "\n";
1177 $jc->unicode_upper (1);
1178 print $jc->run ($in), "\n";
1179 $jc->unicode_escape_all (0);
1180 print $jc->run ($in), "\n";
1181 produces output
1183 "θ΅€γΓΆοΌ‘βΟͺ"
1185 "\u8d64\u30d6\u00f6\uff21\u2182\u03ea"
1186 "\u8D64\u30D6\u00F6\uFF21\u2182\u03EA"
1187 "θ΅€γΓΆοΌ‘βΟͺ"
1188 (This example is included as examples/escape-all.pl
1190 <https://fastapi.metacpan.org/source/BKB/JSON-
1191 Create-0.35/examples/escape-all.pl> in the distribution.)
1192 Output is always UTF-8
1194 Note that JSON::Create contains its own UTF-8 validation, and this
1196 escaping is applied regardless of whether Perl marks the bytes as
1197 "utf8" or not:
1198 use JSON::Create;
1200 no utf8;
1201 my $jc = JSON::Create->new ();
1202 my $in = 'θ΅€γΓΆοΌ‘βΟͺ';
1203 print $jc->run ($in), "\n";
1204 $jc->unicode_escape_all (1);
1205 print $jc->run ($in), "\n";
1206 $jc->unicode_upper (1);
1207 print $jc->run ($in), "\n";
1208 $jc->unicode_escape_all (0);
1209 print $jc->run ($in), "\n";
1210 produces output
1212 "θ΅€γΓΆοΌ‘βΟͺ"
1214 "\u8d64\u30d6\u00f6\uff21\u2182\u03ea"
1215 "\u8D64\u30D6\u00F6\uFF21\u2182\u03EA"
1216 "θ΅€γΓΆοΌ‘βΟͺ"
1217 (This example is included as examples/escape-all-no-utf8.pl
1219 <https://fastapi.metacpan.org/source/BKB/JSON-
1220 Create-0.35/examples/escape-all-no-utf8.pl> in the distribution.)
1221 See also "Input strings must be UTF-8".
1223 unicode_upper
1225 $jc->unicode_upper (1);
1226 Call this with a true value to make Unicode escapes use upper case
1228 letters in the hexadecimal. See the example under "unicode_escape_all".
1229 validate
1231 $jc->validate (1);
1232 If this is called with a true value, JSON::Create validates the user-
1234 generated JSON given by the callbacks registered with "obj",
1235 "type_handler", "obj_handler" and "non_finite_handler". The validation
1236 is done via the routine "assert_valid_json" of JSON::Parse, so that
1237 module must be installed, otherwise the call to "validate" will fail.
1238 This also validates that the return value contains only valid UTF-8.
1239 If JSON::Parse is installed, and the JSON fails to validate, a warning
1241 will be produced containing the invalid JSON string and the error
1242 produced by "assert_valid_json", and the return value will be
1243 undefined.
1244 This method was added in version 0.07 of the module.
1246
1248 This section details what conversions are applied to the various inputs
1249 to produce outputs.
1250 Hashes
1252 JSON::Create turns associative arrays into JSON objects. The keys are
1253 written into JSON as strings, with control characters escaped. The
1254 order of the keys is as they are supplied by Perl.
1255 use JSON::Create 'create_json';
1257 my %example = (
1258 x => 1,
1259 y => 2,
1260 z => 3,
1261 );
1262 print create_json (\%example);
1263 produces output
1265 {"y":2,"x":1,"z":3}
1267 (This example is included as examples/hash.pl
1269 <https://fastapi.metacpan.org/source/BKB/JSON-
1270 Create-0.35/examples/hash.pl> in the distribution.)
1271 Nested hashes are recursively followed:
1273 use JSON::Create 'create_json';
1275 my %example = (
1276 x => {
1277 y => 2,
1278 z => 3,
1279 },
1280 a => {
1281 b => 4,
1282 c => 5,
1283 },
1284 );
1285 print create_json (\%example);
1286 produces output
1288 {"x":{"z":3,"y":2},"a":{"b":4,"c":5}}
1290 (This example is included as examples/nested-hash.pl
1292 <https://fastapi.metacpan.org/source/BKB/JSON-
1293 Create-0.35/examples/nested-hash.pl> in the distribution.)
1294 Arrays
1296 Arrays are converted to JSON arrays. The order of elements of the array
1297 is left unchanged.
1298 use JSON::Create 'create_json';
1300 my @array = (1, 2, 2.5, qw/mocha dusty milky/, qw/Tico Rocky Pinky/);
1301 print create_json (\@array);
1302 produces output
1304 [1,2,2.5,"mocha","dusty","milky","Tico","Rocky","Pinky"]
1306 (This example is included as examples/array.pl
1308 <https://fastapi.metacpan.org/source/BKB/JSON-
1309 Create-0.35/examples/array.pl> in the distribution.)
1310 Nested arrays are recursively followed:
1312 use JSON::Create 'create_json';
1314 my @array = ([1, 2, 2.5], [qw/mocha dusty milky/], [qw/Tico Rocky Pinky/]);
1315 print create_json (\@array);
1316 produces output
1318 [[1,2,2.5],["mocha","dusty","milky"],["Tico","Rocky","Pinky"]]
1320 (This example is included as examples/nested-array.pl
1322 <https://fastapi.metacpan.org/source/BKB/JSON-
1323 Create-0.35/examples/nested-array.pl> in the distribution.)
1324 Nested hashes and arrays are converted similarly:
1326 use JSON::Create 'create_json';
1328 my $nested = {
1329 numbers => [1, 2, 2.5, 99.99],
1330 cats => [qw/mocha dusty milky/],
1331 dogs => [qw/Tico Rocky Pinky/],
1332 fruit => {
1333 thai => 'pineapple',
1334 japan => 'persimmon',
1335 australia => 'orange',
1336 },
1337 };
1338 print create_json ($nested, sort => 1, indent => 1);
1339 produces output
1341 {
1343 "cats":[
1344 "mocha",
1345 "dusty",
1346 "milky"
1347 ],
1348 "dogs":[
1349 "Tico",
1350 "Rocky",
1351 "Pinky"
1352 ],
1353 "fruit":{
1354 "australia":"orange",
1355 "japan":"persimmon",
1356 "thai":"pineapple"
1357 },
1358 "numbers":[
1359 1,
1360 2,
1361 2.5,
1362 99.99
1363 ]
1364 }
1365 (This example is included as examples/nested.pl
1367 <https://fastapi.metacpan.org/source/BKB/JSON-
1368 Create-0.35/examples/nested.pl> in the distribution.)
1369 Scalars
1371 Non-reference Perl scalars are converted to JSON strings or numbers,
1372 depending on what Perl thinks they contain.
1373 Strings
1375 As far as possible, strings are written as they are to the JSON.
1377 JSON is Unicode, so all output is checked for Unicode validity.
1379 Further, this module insists on UTF-8. (See "Input strings must be
1380 UTF-8".) Invalid UTF-8 within input strings produces the error "Invalid
1381 UTF-8" and the undefined value is returned. This behaviour can be
1382 altered with the method "replace_bad_utf8". (For full details of the
1383 corner cases, see "UNICODE HANDLING".)
1384 Some whitespace and control characters must be also escaped for the
1386 output to be valid JSON. (See "RFC 8259".)
1387 In addition to this, "create_json_strict" or the "strict" option reject
1389 inputs containing non-ASCII bytes (bytes with values of from 128 to
1390 255) which are not marked as character strings.
1391 Control characters and whitespace
1393 To form valid JSON, bytes of value less than 0x20 in a Perl string must
1395 be converted into JSON escapes, either the whitespace escapes \b
1396 (backspace) \r, \t, \n, and \f, or the form \u0001 for other control
1397 characters. Further, the backslash must be written as "\\" and double
1398 quotes must be written as "\"".
1399 This example demonstrates some of the necessary escaping:
1401 use JSON::Create 'create_json';
1403 # An example string containing various things.
1404 my $weirdstring = {weird => "\t\r\n\x00 " . '"' . '\\' . '/' };
1405 print create_json ($weirdstring);
1406 produces output
1408 {"weird":"\t\r\n\u0000 \"\\/"}
1410 (This example is included as examples/weirdstring.pl
1412 <https://fastapi.metacpan.org/source/BKB/JSON-
1413 Create-0.35/examples/weirdstring.pl> in the distribution.)
1414 U+2028 and U+2029 (JavaScript clashes)
1416 my $out = create_json (["\x{2028}"]);
1418 # $out = '["\u2028"]'
1419 Although it is not required by the JSON standard, JSON::Create by
1421 default escapes Unicode code points U+2028 and U+2029 as "\u2028" and
1422 "\u2029" for JavaScript compatibility. This behaviour can be altered
1423 with the method "no_javascript_safe".
1424 This escaping is necessary for JavaScript because of a clash between
1426 the JSON standard and the JavaScript (ECMAScript) standard. The
1427 characters U+2028 ("LINE SEPARATOR" in the Unicode standard) and U+2029
1428 ("PARAGRAPH SEPARATOR" in the Unicode standard) are valid within JSON,
1429 as defined by "RFC 8259", but invalid within JavaScript strings, as
1430 defined by the ECMA standard (See ECMA Standard ECMA-262, "ECMAScript
1431 Language Specification", 3rd Edition, section 7.3 "Line Terminators").
1432 Other escapes
1434 The forward slash, /, known as "solidus" in the JSON specification,
1436 does not have to be escaped, and JSON::Create's default is not to
1437 escape it. This behaviour can be altered with the method
1438 "escape_slash".
1439 Other Unicode values are not escaped. This behaviour can be altered
1441 with the method "unicode_escape_all".
1442 Integers
1444 Integers are printed in the usual way. Perl may interpret an integer
1446 with a very large absolute value to be a floating point number, and
1447 this module will print it out as such. See also "Context-dependent
1448 variables" for the handling of variables with both string and integer
1449 values.
1450 Floating point numbers
1452 Finite floating point numbers are printed using printf formatting via
1454 "%g", like
1455 printf ("%g", $number);
1457 This behaviour can be altered with the method "set_fformat"
1459 JSON does not allow NaN or infinity as bare values. From page 6 of "RFC
1461 8259":
1462 Numeric values that cannot be represented in the grammar below
1464 (such as Infinity and NaN) are not permitted.
1465 "create_json" converts NaN (not a number) values to "nan" (the letters
1467 "nan" surrounded by double quotes), and positive and negative infinity
1468 to "inf" and "-inf" respectively.
1469 "create_json_strict" disallows non-finite numbers. If a non-finite
1471 number appears within its input, it prints a warning "Non-finite number
1472 in input" and returns the undefined value:
1473 use JSON::Create 'create_json_strict';
1475 print create_json_strict (9**9**9);
1476 produces output
1478 Non-finite number in input at /usr/home/ben/projects/json-create/blib/lib/JSON/Create.pm line 200.
1480 Use of uninitialized value in print at /usr/home/ben/projects/json-create/examples/strict-non-finite.pl line 5.
1481 (This example is included as examples/strict-non-finite.pl
1483 <https://fastapi.metacpan.org/source/BKB/JSON-
1484 Create-0.35/examples/strict-non-finite.pl> in the distribution.)
1485 A JSON::Create object created with "new" converts in the same way as
1487 "create_json". This behaviour can be altered with the method
1488 "non_finite_handler". If "strict" is specified, non-finite numbers are
1489 passed to "non_finite_handler" if it is set, and if not, it prints a
1490 warning "Non-finite number in input" and returns the undefined value.
1491 The undefined value
1493 Undefined values in the input are mapped to the JSON literal "null".
1495 use JSON::Create 'create_json';
1497 print create_json ({a => undef, b => [undef, undef]}), "\n";
1498 produces output
1500 {"a":null,"b":[null,null]}
1502 (This example is included as examples/undef.pl
1504 <https://fastapi.metacpan.org/source/BKB/JSON-
1505 Create-0.35/examples/undef.pl> in the distribution.)
1506 Booleans
1508 Booleans ("true" and "false") from input via JSON::Parse version 0.37
1510 or later will be turned into the outputs "true" and "false":
1511 use JSON::Parse '0.38', 'parse_json';
1513 use JSON::Create 'create_json';
1514 my $in = parse_json ('[true,false,"boo"]');
1515 print create_json ($in);
1516 produces output
1518 [true,false,"boo"]
1520 (This example is included as examples/json-parse-bool.pl
1522 <https://fastapi.metacpan.org/source/BKB/JSON-
1523 Create-0.35/examples/json-parse-bool.pl> in the distribution.)
1524 Other kinds of object can be converted to booleans using the method
1526 "bool" (see below).
1527 Context-dependent variables
1529 A context-dependent variable is a variable which may contain a string
1531 and a numerical value. Usually the string value is just a
1532 representation of the number, but it may not be. The behaviour in the
1533 case of a context-dependent variable is as follows.
1534 If the variable contains a valid numerical value, the numerical value
1536 is used in the output JSON, rather than the string value. However, some
1537 modules, like "charinfo" in Unicode::UCD, return context-dependent hash
1538 values which have a non-number-like string under the key "script" with
1539 values such as "Latin" or "Common" but no valid numerical value,
1540 despite being marked as context-dependent variables. In such cases, the
1541 string value is used. (In terms of XS, if the scalar is marked as
1542 "SVt_PVIV" or "SVt_PVNV", the scalar is tested with "SvIOK" or "SvNOK"
1543 respectively, and if this is true the numerical value is used, if false
1544 the string value is used.)
1545 Up to version 0.25, this module wrongly assumed that the string part of
1547 a context-dependent variable would always be a valid representation of
1548 a number, and the string was added to the output without quote marks.
1549 In version 0.26, checking was done to see if the string actually was a
1550 number. In version 0.27 this approach was abandoned and the numerical
1551 value was given precedence. In version 0.28 this was again altered for
1552 the sake of unusual cases like the "script" key returned by "charinfo"
1553 in Unicode::UCD, where the scalar is marked as having a numerical value
1554 but does not in fact contain a valid numerical value.
1555 Other types
1557 JSON::Create is meant to provide serialization of data types. It does
1558 not provide built-in serialization of Perl objects and other non-data
1559 types, such as code references or regular expressions, beyond a few
1560 basic defaults. How to handle non-data types is left completely up to
1561 users. These basic defaults, and how to set up more extensive handling,
1562 are described in the following subsections.
1563 Scalar references
1565 "create_json" dereferences scalar references, then treats them as
1567 scalars in the way described in "Scalars".
1568 "create_json_strict" rejects scalar references. Input containing a
1570 scalar reference causes a warning "Input's type cannot be serialized to
1571 JSON" and the undefined value to be returned.
1572 A JSON::Create object created with "new" behaves as "create_json"
1574 unless the "strict" option is specified. If the strict option is
1575 specified, scalar references are passed through to "type_handler" if it
1576 is set, otherwise input containing a scalar reference causes a warning
1577 "Input's type cannot be serialized to JSON" and the undefined value to
1578 be returned.
1579 Objects
1581 "create_json" handles Perl objects as if non-object types. In other
1583 words, unless you specify object handling, it breaks encapsulation.
1584 "create_json_strict" rejects input containing Perl objects. If the
1586 input contains an object (a blessed reference), a warning "Object
1587 cannot be serialized to JSON" is printed and the undefined value
1588 returned.
1589 A JSON::Create object created with "new" can handle specified types of
1591 object with method "obj", or with a general object handler supplied via
1592 "obj_handler". By default it behaves like "create_json". If "strict" is
1593 chosen, it rejects input containing Perl objects unless the user sets a
1594 handler for them with "obj" or "obj_handler".
1595 Code, regexes, and other references
1597 A code or other reference (regexes, globs, etc.) in the input of
1599 "create_json" or "create_json_strict" prints a warning "Input's type
1600 cannot be serialized to JSON" and causes the entire return value to be
1601 the undefined value. This behaviour can be altered with the method
1602 "type_handler".
1603
1605 The module exports nothing except by request. Two functions,
1606 "create_json" and "create_json_strict", are exported on request. There
1607 is also an export tag "all" if you require both functions:
1608 use JSON::Create ':all';
1610
1612 The module uses C internally, so you need a C compiler to install it.
1613 If the compiled library cannot be loaded, there is also a backup "pure
1614 Perl" module JSON::Create::PP in the distribution.
1615
1617 This section details JSON::Create's handling of Unicode within strings.
1618 This involves the distinction between two things with confusingly
1619 similar names, Perl character strings, "utf8", and the Unicode encoding
1620 "UTF-8".
1621 UTF-8 only
1623 JSON::Create only consumes and produces the UTF-8 encoding of
1624 Unicode. If you need a different encoding, please use the Encode
1625 module to encode the output.
1626 Input strings must be UTF-8
1628 All strings within the input must be UTF-8 encoded. This does not
1629 mean that the strings must be Perl character strings (Perl's
1630 "utf8"), it means that input strings must be valid UTF-8. Input
1631 strings can be either Perl character strings or bytes, but in
1632 either case the bytes of the string must be valid UTF-8.
1633 To illustrate this, examine the following example:
1635 use JSON::Create 'create_json';
1637 use utf8;
1638 $| = 1;
1639 print create_json ('θ΅€γΓΆοΌ‘βΟͺ'), "\n";
1640 no utf8;
1641 binmode STDOUT, ":raw";
1642 print create_json ('θ΅€γΓΆοΌ‘βΟͺ'), "\n";
1643 print create_json ("\x99\xff\x10"), "\n";
1644 produces output
1646 "θ΅€γΓΆοΌ‘βΟͺ"
1648 "θ΅€γΓΆοΌ‘βΟͺ"
1649 Invalid UTF-8 at /usr/home/ben/projects/json-create/blib/lib/JSON/Create.pm line 192.
1650 Use of uninitialized value in print at /usr/home/ben/projects/json-create/examples/valid-chars.pl line 12.
1651 (This example is included as examples/valid-chars.pl
1653 <https://fastapi.metacpan.org/source/BKB/JSON-
1654 Create-0.35/examples/valid-chars.pl> in the distribution.)
1655 The point here is that the UTF-8 validation is carried out
1657 regardless of whether Perl thinks that the input string is "utf8".
1658 The string in the third call to "create_json" is not marked as utf8
1659 by Perl but still fails as invalid UTF-8.
1660 JSON::Create's insistence on UTF-8 within input strings is related
1662 to "Unicode upgrades are not done according to Perl conventions".
1663 Output is valid UTF-8
1665 All of the output of either the function "create_json" or the
1666 method "create" is valid UTF-8. This does not mean that output
1667 strings are marked as Perl character strings ("utf8"), it means
1668 that the output has been validated as UTF-8.
1669 There is one exception to this. In the case of user-generated JSON
1671 returned by "obj", "obj_handler", "type_handler" and
1672 "non_finite_handler", the parts of the output consisting of return
1673 values from user routines may be non-UTF-8-compliant if the user
1674 has not switched on validation with "validate", and there are no
1675 character strings ("utf8") anywhere in the input. However, if there
1676 are any Perl character strings ("utf8") anywhere in the input, and
1677 the user has not chosen "downgrade_utf8", JSON::Create validates
1678 the entire output as UTF-8, as described in "UTF-8 validation of
1679 user-supplied JSON".
1680 Unicode upgrades are not done according to Perl conventions
1682 If a single string anywhere in the input is a Perl character
1683 string, in other words marked as "utf8", the entire output string
1684 is marked as a Perl character string, "utf8", without altering the
1685 non-"utf8" bytes. This is at odds with Perl conventions. Perl says
1686 that non-"utf8" strings actually consist of characters with symbols
1687 from 0 to 255 which "coincidentally" fit into one byte, and "utf8"
1688 strings actually consist of characters with values from 0 to
1689 0x10FFFF, not bytes, and when combining the two, it is illegal to
1690 treat either of these as bytes, but instead they must both be
1691 treated as numbers. To illustrate this, here is the behaviour of
1692 JSON contrasted with JSON::Create:
1693 use utf8;
1695 use FindBin '$Bin';
1696 use JSON;
1697 use JSON::Create 'create_json';
1698 no utf8;
1699 my $x = 'γγγγγ';
1700 use utf8;
1701 my $y = 'γγγγγ';
1702 my $v = {x => $x, y => $y};
1703 print to_json ($v), "\n";
1704 print create_json ($v), "\n";
1705 produces output
1707 {"x":"Γ£ΒΒΓ£ΒΒΓ£ΒΒΓ£ΒΒΓ£ΒΒ","y":"γγγγγ"}
1709 {"x":"γγγγγ","y":"γγγγγ"}
1710 (This example is included as examples/json-unicode.pl
1712 <https://fastapi.metacpan.org/source/BKB/JSON-
1713 Create-0.35/examples/json-unicode.pl> in the distribution.)
1714 The Perl convention is that if a non-utf8 string and a utf8 string
1716 are combined, they should be combined as JSON does it, by treating
1717 each byte of the non-utf8 string as if it is a single Unicode code
1718 point, and writing equivalent UTF-8 bytes for that code point into
1719 the output. JSON::Create does a different thing, which is to insist
1720 that all input strings must be valid UTF-8, and after validating
1721 them, it combines them with the "utf8" strings without altering
1722 their contents. This break with the Perl convention is by design.
1723 This example illustrates what happens with non-UTF-8 bytes:
1725 use JSON;
1727 use JSON::Create 'create_json';
1728 use Gzip::Faster;
1729 $|=1;
1730 # Generate some random garbage bytes
1731 my $x = gzip ('γγγγγ');
1732 use utf8;
1733 my $y = 'γγγγγ';
1734 my $v = {x => $x, y => $y};
1735 print to_json ($v), "\n";
1736 print create_json ($v), "\n";
1737 produces output
1739 {"x":"\u001fΒ\b\u0000\u0000\u0000\u0000\u0000\u0000\u0003{ΓΓΓ½ΒΈΒ±Γ·qcΓΏΓ£ΓΒΒ\u001b'\u0003\u0000Β£ Β³\u0012\u000f\u0000\u0000\u0000","y":"γγγγγ"}
1741 Invalid UTF-8 at /usr/home/ben/projects/json-create/blib/lib/JSON/Create.pm line 192.
1742 Use of uninitialized value in print at /usr/home/ben/projects/json-create/examples/json-unicode-gzip-bytes.pl line 15.
1743 (This example is included as examples/json-unicode-gzip-bytes.pl
1745 <https://fastapi.metacpan.org/source/BKB/JSON-
1746 Create-0.35/examples/json-unicode-gzip-bytes.pl> in the
1747 distribution.)
1748 Using replace_bad_utf8 may cause a utf8 upgrade
1750 Please see the discussion under "replace_bad_utf8".
1751 UTF-8 validation of user-supplied JSON
1753 If you supply JSON via a user routine such as "obj_handler", and
1754 you choose not to validate your output with "validate", and the
1755 input contains a character string ("utf8"), and you do not choose
1756 "downgrade_utf8", the entire output string has to be validated as
1757 UTF-8, to prevent a loophole where a string containing non-UTF-8
1758 compliant bytes could get upgraded to a character string ("utf8").
1759 In this case, if invalid UTF-8 is detected, the diagnostic "Invalid
1761 UTF-8 from user routine" is printed, and the undefined value
1762 returned. Since the check is applied to the final output JSON,
1763 there is no information about which routine was at fault, so to get
1764 a more specific diagnosis, please switch on "validate".
1765 Here is an example of how this may occur:
1767 use JSON::Create;
1769 my $jc = JSON::Create->new ();
1770 # This type handler returns a non-UTF-8 string.
1771 $jc->type_handler (sub {return '"'. pack ("CCC", 0x99, 0x10, 0x0) . '"';});
1772 use utf8;
1773 # sub {1} triggers the type handler for a code reference, and the γΆγΌ
1774 # contains a "utf8" flag, so this combination sets off the problem.
1775 print $jc->run ({a => sub {1}, b => 'γΆγΌ'});
1776 produces output
1778 Invalid UTF-8 from user routine at /usr/home/ben/projects/json-create/examples/user-bad-utf8.pl line 11.
1780 Use of uninitialized value in print at /usr/home/ben/projects/json-create/examples/user-bad-utf8.pl line 11.
1781 (This example is included as examples/user-bad-utf8.pl
1783 <https://fastapi.metacpan.org/source/BKB/JSON-
1784 Create-0.35/examples/user-bad-utf8.pl> in the distribution.)
1785
1787 All diagnostics are warnings by default. This behaviour can be altered
1788 with the method "fatal_errors".
1789 Input's type cannot be serialized to JSON
1791 (Warning) A reference type such as a code reference, regexp, or
1792 glob was found in the user's input. For a discussion, see "Code,
1793 regexes, and other references". For how to overcome this, see
1794 "type_handler".
1795 Invalid UTF-8
1797 (Warning) Bytes in a Perl string were not valid UTF-8. This
1798 behaviour can be altered with the method "replace_bad_utf8".
1799 Invalid UTF-8 from user routine
1801 (Warning) A return value from a user routine was not valid UTF-8.
1802 See "UTF-8 validation of user-supplied JSON".
1803 This diagnostic and the corresponding validation of user-supplied
1805 JSON was added in version 0.19 of the module.
1806 JSON::Parse::assert_valid_json failed
1808 (Warning) The user requested validation with "validate" and this
1809 failed.
1810 Non-ASCII byte in non-utf8 string
1812 (Warning) The user tried to encode a string containing a non-ASCII
1813 byte in a non-"utf8" string. This diagnostic occurs with either
1814 "create_json_strict" or "strict".
1815 This diagnostic was added in version 0.20 of the module together
1817 with "create_json_strict" and the "strict" method.
1818 Non-finite number in input
1820 (Warning) A number which cannot be represented as a floating point
1821 number was found in the input. See "Floating point numbers".
1822 This diagnostic was added in version 0.20 of the module together
1824 with "create_json_strict" and the "strict" method.
1825 Object cannot be serialized to JSON
1827 (Warning) An object in the input could not be serialized to JSON.
1828 See "Objects" for a discussion.
1829 This diagnostic was added in version 0.20 of the module together
1831 with "create_json_strict" and the "strict" method.
1832 Undefined value from user routine
1834 (Warning) An undefined value was returned by a user routine set
1835 with either "obj", "obj_handler", "type_handler" or
1836 "non_finite_handler".
1837
1839 There is a benchmarking script in bench/bench.pl which compares the
1840 performance of the module with JSON::XS and Cpanel::JSON::XS. Outputs
1841 look like this, where the "improve" column is the improvement in speed
1842 of the fastest module compared to the slowest:
1843 Versions used:
1845 +-----+------------------+---------+
1846 | CJX | Cpanel::JSON::XS | 4.25 |
1847 +-----+------------------+---------+
1848 | JX | JSON::XS | 4.03 |
1849 +-----+------------------+---------+
1850 | JC | JSON::Create | 0.29_02 |
1851 +-----+------------------+---------+
1852 Comparing hash of ASCII strings...
1853 Repetitions: 1000 x 200 = 200000
1855 +--------+--------+------------+---------+
1856 | Module | 1/min | min | improve |
1857 +--------+--------+------------+---------+
1858 | CJX | 380539 | 0.00262785 | 1 |
1859 | JC | 755322 | 0.00132394 | 1.98487 |
1860 | JX | 672056 | 0.00148797 | 1.76606 |
1861 +--------+--------+------------+---------+
1862 Comparing hash of integers...
1864 Repetitions: 1000 x 200 = 200000
1866 +--------+--------+------------+---------+
1867 | Module | 1/min | min | improve |
1868 +--------+--------+------------+---------+
1869 | CJX | 157604 | 0.00634503 | 1 |
1870 | JC | 388038 | 0.00257707 | 2.46211 |
1871 | JX | 199245 | 0.00501895 | 1.26422 |
1872 +--------+--------+------------+---------+
1873 Comparing hash of Unicode strings...
1875 Repetitions: 1000 x 200 = 200000
1877 +--------+-------------+-------------+---------+
1878 | Module | 1/min | min | improve |
1879 +--------+-------------+-------------+---------+
1880 | CJX | 513127 | 0.00194883 | 1 |
1881 | JC | 1.04831e+06 | 0.000953913 | 2.04299 |
1882 | JX | 808463 | 0.00123692 | 1.57556 |
1883 +--------+-------------+-------------+---------+
1884 Comparing array of floats...
1886 Repetitions: 1000 x 200 = 200000
1888 +--------+--------+------------+---------+
1889 | Module | 1/min | min | improve |
1890 +--------+--------+------------+---------+
1891 | CJX | 136707 | 0.00731492 | 1 |
1892 | JC | 342001 | 0.00292397 | 2.50171 |
1893 | JX | 156961 | 0.00637102 | 1.14816 |
1894 +--------+--------+------------+---------+
1895 Comparing array of ASCII strings...
1897 Repetitions: 1000 x 200 = 200000
1899 +--------+--------+------------+---------+
1900 | Module | 1/min | min | improve |
1901 +--------+--------+------------+---------+
1902 | CJX | 279881 | 0.00357294 | 1 |
1903 | JC | 547059 | 0.00182796 | 1.95461 |
1904 | JX | 487766 | 0.00205016 | 1.74276 |
1905 +--------+--------+------------+---------+
1906
1908 There is currently no way to delete object handlers set via "obj" from
1909 a JSON::Create object.
1910 There are a few remaining undecided issues around the default object
1912 serialization.
1913 No warning is printed when the user uses clashing methods like "bool"
1915 and "obj_handler".
1916 There is a bug in JSON::Create::PP's handling of non-integer numbers.
1918 The floating point printing loses precision on round trips.
1920
1922 "set_fformat" was added in version 0.07.
1923 "validate" was added in version 0.07.
1925 "fatal_errors" was added in version 0.10.
1927 "replace_bad_utf8" was added in version 0.12.
1929 "obj_handler" was added in version 0.13. This version also added
1931 loading of the Pure-Perl version of the module, JSON::Create::PP, if
1932 the loading of JSON::Create failed.
1933 "non_finite_handler" was added in version 0.17.
1935 "downgrade_utf8" was added in version 0.18.
1937 The "Invalid UTF-8 from user routine" diagnostic was added in version
1939 0.19.
1940 The "create_json_strict" function and "strict" methods and associated
1942 diagnostics were added in version 0.20.
1943 Indentation was added for objects with "indent" in version 0.27.
1945 Version 0.28 altered the handling of context-dependent variables to use
1947 the numerical part as a JSON number if valid, and the string part as a
1948 JSON string if not a valid number. See "Context-dependent variables"
1949 for all the details.
1950 Arguments to "create_json" and "create_json_strict", and the methods
1952 "set", "sort" and "cmp" were added in version 0.29.
1953 Version 0.30 rewrote "set" and related routines in XS and increased the
1955 speed of the module, and added "write_json".
1956 In version 0.31, the method "run" was renamed "create".
1958 Old names
1960 run The method "run" was renamed "create" in version 0.31. The old name
1961 is not deprecated and will continue to work indefinitely.
1962
1964 JSON::Create::PP
1965 This is a backup module for JSON::Create in pure Perl.
1966 RFC 8259
1968 RFC 8259 "The JavaScript Object Notation (JSON) Data Interchange
1969 Format" <https://www.ietf.org/rfc/rfc8259.txt>
1970 "SEE ALSO" in JSON::Parse
1972 Please refer to "SEE ALSO" in JSON::Parse for information on the
1973 specifications for JSON and a list of other CPAN modules for JSON.
1974 Installing from the github repository
1976 Experimentally, it is possible to install this module from Github. You
1977 will also need to install Template and possibly some other modules.
1978 Blog posts
1980 There are some blog posts about the JSON::Create internals of interest
1981 to Perl XS programmers here:
1982 Using a user-defined sort order from XS
1984 <http://blogs.perl.org/users/ben_bullock/2020/12/alles-in-ordnung.html>
1985 The mysterious case of the SVt_PVIV
1986 <http://blogs.perl.org/users/ben_bullock/2020/11/the-mysterious-case-
1987 of-the-svt-pviv.html>
1988 JSON::Create now features indentation
1989 <http://blogs.perl.org/users/ben_bullock/2020/11/jsoncreate-now-
1990 features-indentation.html>
1991 av_fetch can return NULL
1992 <http://blogs.perl.org/users/ben_bullock/2020/02/av-fetch-can-return-
1993 null.html>
1994 Muddled numbers & strings <https://benbullock.substack.com/p/muddled-
1995 numbers-and-strings>
1996 This relates to the bug dealing with floating point and integer
1997 numbers found in version 0.33.
1998
2000 Ben Bullock, <bkb@cpan.org>
2001
2003 This package and associated files are copyright (C) 2015-2021 Ben
2004 Bullock.
2005 You can use, copy, modify and redistribute this package and associated
2007 files under the Perl Artistic Licence or the GNU General Public
2008 Licence.
2009 The sorting code used by "cmp" comes from the FreeBSD source code and
2011 is copyright by the Regents of the University of California.
2012perl v5.34.0 2021-07-22 JSON::Create(3)