… | |
… | |
101 | |
101 | |
102 | package JSON::XS; |
102 | package JSON::XS; |
103 | |
103 | |
104 | use common::sense; |
104 | use common::sense; |
105 | |
105 | |
106 | our $VERSION = 2.34; |
106 | our $VERSION = '3.0'; |
107 | our @ISA = qw(Exporter); |
107 | our @ISA = qw(Exporter); |
108 | |
108 | |
109 | our @EXPORT = qw(encode_json decode_json); |
109 | our @EXPORT = qw(encode_json decode_json); |
110 | |
110 | |
111 | use Exporter; |
111 | use Exporter; |
… | |
… | |
467 | |
467 | |
468 | =item $json = $json->allow_blessed ([$enable]) |
468 | =item $json = $json->allow_blessed ([$enable]) |
469 | |
469 | |
470 | =item $enabled = $json->get_allow_blessed |
470 | =item $enabled = $json->get_allow_blessed |
471 | |
471 | |
|
|
472 | See L<OBJECT SERIALISATION> for details. |
|
|
473 | |
472 | If C<$enable> is true (or missing), then the C<encode> method will not |
474 | If C<$enable> is true (or missing), then the C<encode> method will not |
473 | barf when it encounters a blessed reference. Instead, the value of the |
475 | barf when it encounters a blessed reference that it cannot convert |
474 | B<convert_blessed> option will decide whether C<null> (C<convert_blessed> |
476 | otherwise. Instead, a JSON C<null> value is encoded instead of the object. |
475 | disabled or no C<TO_JSON> method found) or a representation of the |
|
|
476 | object (C<convert_blessed> enabled and C<TO_JSON> method found) is being |
|
|
477 | encoded. Has no effect on C<decode>. |
|
|
478 | |
477 | |
479 | If C<$enable> is false (the default), then C<encode> will throw an |
478 | If C<$enable> is false (the default), then C<encode> will throw an |
480 | exception when it encounters a blessed object. |
479 | exception when it encounters a blessed object that it cannot convert |
|
|
480 | otherwise. |
|
|
481 | |
|
|
482 | This setting has no effect on C<decode>. |
481 | |
483 | |
482 | =item $json = $json->convert_blessed ([$enable]) |
484 | =item $json = $json->convert_blessed ([$enable]) |
483 | |
485 | |
484 | =item $enabled = $json->get_convert_blessed |
486 | =item $enabled = $json->get_convert_blessed |
|
|
487 | |
|
|
488 | See L<OBJECT SERIALISATION> for details. |
485 | |
489 | |
486 | If C<$enable> is true (or missing), then C<encode>, upon encountering a |
490 | If C<$enable> is true (or missing), then C<encode>, upon encountering a |
487 | blessed object, will check for the availability of the C<TO_JSON> method |
491 | blessed object, will check for the availability of the C<TO_JSON> method |
488 | on the object's class. If found, it will be called in scalar context |
492 | on the object's class. If found, it will be called in scalar context and |
489 | and the resulting scalar will be encoded instead of the object. If no |
493 | the resulting scalar will be encoded instead of the object. |
490 | C<TO_JSON> method is found, the value of C<allow_blessed> will decide what |
|
|
491 | to do. |
|
|
492 | |
494 | |
493 | The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON> |
495 | The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON> |
494 | returns other blessed objects, those will be handled in the same |
496 | returns other blessed objects, those will be handled in the same |
495 | way. C<TO_JSON> must take care of not causing an endless recursion cycle |
497 | way. C<TO_JSON> must take care of not causing an endless recursion cycle |
496 | (== crash) in this case. The name of C<TO_JSON> was chosen because other |
498 | (== crash) in this case. The name of C<TO_JSON> was chosen because other |
497 | methods called by the Perl core (== not by the user of the object) are |
499 | methods called by the Perl core (== not by the user of the object) are |
498 | usually in upper case letters and to avoid collisions with any C<to_json> |
500 | usually in upper case letters and to avoid collisions with any C<to_json> |
499 | function or method. |
501 | function or method. |
500 | |
502 | |
501 | This setting does not yet influence C<decode> in any way, but in the |
503 | If C<$enable> is false (the default), then C<encode> will not consider |
502 | future, global hooks might get installed that influence C<decode> and are |
504 | this type of conversion. |
503 | enabled by this setting. |
|
|
504 | |
505 | |
505 | If C<$enable> is false, then the C<allow_blessed> setting will decide what |
506 | This setting has no effect on C<decode>. |
506 | to do when a blessed object is found. |
507 | |
|
|
508 | =item $json = $json->allow_tags ([$enable]) |
|
|
509 | |
|
|
510 | =item $enabled = $json->allow_tags |
|
|
511 | |
|
|
512 | See L<OBJECT SERIALISATION> for details. |
|
|
513 | |
|
|
514 | If C<$enable> is true (or missing), then C<encode>, upon encountering a |
|
|
515 | blessed object, will check for the availability of the C<FREEZE> method on |
|
|
516 | the object's class. If found, it will be used to serialise the object into |
|
|
517 | a nonstandard tagged JSON value (that JSON decoders cannot decode). |
|
|
518 | |
|
|
519 | It also causes C<decode> to parse such tagged JSON values and deserialise |
|
|
520 | them via a call to the C<THAW> method. |
|
|
521 | |
|
|
522 | If C<$enable> is false (the default), then C<encode> will not consider |
|
|
523 | this type of conversion, and tagged JSON values will cause a parse error |
|
|
524 | in C<decode>, as if tags were not part of the grammar. |
507 | |
525 | |
508 | =item $json = $json->filter_json_object ([$coderef->($hashref)]) |
526 | =item $json = $json->filter_json_object ([$coderef->($hashref)]) |
509 | |
527 | |
510 | When C<$coderef> is specified, it will be called from C<decode> each |
528 | When C<$coderef> is specified, it will be called from C<decode> each |
511 | time it decodes a JSON object. The only argument is a reference to the |
529 | time it decodes a JSON object. The only argument is a reference to the |
… | |
… | |
986 | |
1004 | |
987 | =item null |
1005 | =item null |
988 | |
1006 | |
989 | A JSON null atom becomes C<undef> in Perl. |
1007 | A JSON null atom becomes C<undef> in Perl. |
990 | |
1008 | |
|
|
1009 | =item shell-style comments (C<< # I<text> >>) |
|
|
1010 | |
|
|
1011 | As a nonstandard extension to the JSON syntax that is enabled by the |
|
|
1012 | C<relaxed> setting, shell-style comments are allowed. They can start |
|
|
1013 | anywhere outside strings and go till the end of the line. |
|
|
1014 | |
|
|
1015 | =item tagged values (C<< (I<tag>)I<value> >>). |
|
|
1016 | |
|
|
1017 | Another nonstandard extension to the JSON syntax, enabled with the |
|
|
1018 | C<allow_tags> setting, are tagged values. In this implementation, the |
|
|
1019 | I<tag> must be a perl package/class name encoded as a JSON string, and the |
|
|
1020 | I<value> must be a JSON array encoding optional constructor arguments. |
|
|
1021 | |
|
|
1022 | See L<OBJECT SERIALISATION>, below, for details. |
|
|
1023 | |
991 | =back |
1024 | =back |
992 | |
1025 | |
993 | |
1026 | |
994 | =head2 PERL -> JSON |
1027 | =head2 PERL -> JSON |
995 | |
1028 | |
… | |
… | |
1032 | and JSON false values, respectively. You can also use C<\1> and C<\0> |
1065 | and JSON false values, respectively. You can also use C<\1> and C<\0> |
1033 | directly if you want. |
1066 | directly if you want. |
1034 | |
1067 | |
1035 | =item blessed objects |
1068 | =item blessed objects |
1036 | |
1069 | |
1037 | Blessed objects are not directly representable in JSON. See the |
1070 | Blessed objects are not directly representable in JSON, but C<JSON::XS> |
1038 | C<allow_blessed> and C<convert_blessed> methods on various options on |
1071 | allows various ways of handling objects. See L<OBJECT SERIALISATION>, |
1039 | how to deal with this: basically, you can choose between throwing an |
1072 | below, for details. |
1040 | exception, encoding the reference as if it weren't blessed, or provide |
|
|
1041 | your own serialiser method. |
|
|
1042 | |
1073 | |
1043 | =item simple scalars |
1074 | =item simple scalars |
1044 | |
1075 | |
1045 | Simple Perl scalars (any scalar that is not a reference) are the most |
1076 | Simple Perl scalars (any scalar that is not a reference) are the most |
1046 | difficult objects to encode: JSON::XS will encode undefined scalars as |
1077 | difficult objects to encode: JSON::XS will encode undefined scalars as |
… | |
… | |
1082 | extensions to the floating point numbers of your platform, such as |
1113 | extensions to the floating point numbers of your platform, such as |
1083 | infinities or NaN's - these cannot be represented in JSON, and it is an |
1114 | infinities or NaN's - these cannot be represented in JSON, and it is an |
1084 | error to pass those in. |
1115 | error to pass those in. |
1085 | |
1116 | |
1086 | =back |
1117 | =back |
|
|
1118 | |
|
|
1119 | =head2 OBJECT SERIALISATION |
|
|
1120 | |
|
|
1121 | As JSON cannot directly represent Perl objects, you have to choose between |
|
|
1122 | a pure JSON representation (without the ability to deserialise the object |
|
|
1123 | automatically again), and a nonstandard extension to the JSON syntax, |
|
|
1124 | tagged values. |
|
|
1125 | |
|
|
1126 | =head3 SERIALISATION |
|
|
1127 | |
|
|
1128 | What happens when C<JSON::XS> encounters a Perl object depends on the |
|
|
1129 | C<allow_blessed>, C<convert_blessed> and C<allow_tags> settings, which are |
|
|
1130 | used in this order: |
|
|
1131 | |
|
|
1132 | =over 4 |
|
|
1133 | |
|
|
1134 | =item 1. C<allow_tags> is enabled and the object has a C<FREEZE> method. |
|
|
1135 | |
|
|
1136 | In this case, C<JSON::XS> uses the L<Types::Serialiser> object |
|
|
1137 | serialisation protocol to create a tagged JSON value, using a nonstandard |
|
|
1138 | extension to the JSON syntax. |
|
|
1139 | |
|
|
1140 | This works by invoking the C<FREEZE> method on the object, with the first |
|
|
1141 | argument being the object to serialise, and the second argument being the |
|
|
1142 | constant string C<JSON> to distinguish it from other serialisers. |
|
|
1143 | |
|
|
1144 | The C<FREEZE> method can return any number of values (i.e. zero or |
|
|
1145 | more). These values and the paclkage/classname of the object will then be |
|
|
1146 | encoded as a tagged JSON value in the following format: |
|
|
1147 | |
|
|
1148 | ("classname")[FREEZE return values...] |
|
|
1149 | |
|
|
1150 | For example, the hypothetical C<My::Object> C<FREEZE> method might use the |
|
|
1151 | objects C<type> and C<id> members to encode the object: |
|
|
1152 | |
|
|
1153 | sub My::Object::FREEZE { |
|
|
1154 | my ($self, $serialiser) = @_; |
|
|
1155 | |
|
|
1156 | ($self->{type}, $self->{id}) |
|
|
1157 | } |
|
|
1158 | |
|
|
1159 | =item 2. C<convert_blessed> is enabled and the object has a C<TO_JSON> method. |
|
|
1160 | |
|
|
1161 | In this case, the C<TO_JSON> method of the object is invoked in scalar |
|
|
1162 | context. It must return a single scalar that can be directly encoded into |
|
|
1163 | JSON. This scalar replaces the object in the JSON text. |
|
|
1164 | |
|
|
1165 | For example, the following C<TO_JSON> method will convert all L<URI> |
|
|
1166 | objects to JSON strings when serialised. The fatc that these values |
|
|
1167 | originally were L<URI> objects is lost. |
|
|
1168 | |
|
|
1169 | sub URI::TO_JSON { |
|
|
1170 | my ($uri) = @_; |
|
|
1171 | $uri->as_string |
|
|
1172 | } |
|
|
1173 | |
|
|
1174 | =item 3. C<allow_blessed> is enabled. |
|
|
1175 | |
|
|
1176 | The object will be serialised as a JSON null value. |
|
|
1177 | |
|
|
1178 | =item 4. none of the above |
|
|
1179 | |
|
|
1180 | If none of the settings are enabled or the respective methods are missing, |
|
|
1181 | C<JSON::XS> throws an exception. |
|
|
1182 | |
|
|
1183 | =back |
|
|
1184 | |
|
|
1185 | =head3 DESERIALISATION |
|
|
1186 | |
|
|
1187 | For deserialisation there are only two cases to consider: either |
|
|
1188 | nonstandard tagging was used, in which case C<allow_tags> decides, |
|
|
1189 | or objects cannot be automatically be deserialised, in which |
|
|
1190 | case you can use postprocessing or the C<filter_json_object> or |
|
|
1191 | C<filter_json_single_key_object> callbacks to get some real objects our of |
|
|
1192 | your JSON. |
|
|
1193 | |
|
|
1194 | This section only considers the tagged value case: I a tagged JSON object |
|
|
1195 | is encountered during decoding and C<allow_tags> is disabled, a parse |
|
|
1196 | error will result (as if tagged values were not part of the grammar). |
|
|
1197 | |
|
|
1198 | If C<allow_tags> is enabled, C<JSON::XS> will look up the C<THAW> method |
|
|
1199 | of the package/classname used during serialisation (it will not attempt |
|
|
1200 | to load the package as a Perl module). If there is no such method, the |
|
|
1201 | decoding will fail with an error. |
|
|
1202 | |
|
|
1203 | Otherwise, the C<THAW> method is invoked with the classname as first |
|
|
1204 | argument, the constant string C<JSON> as second argument, and all the |
|
|
1205 | values from the JSON array (the values originally returned by the |
|
|
1206 | C<FREEZE> method) as remaining arguments. |
|
|
1207 | |
|
|
1208 | The method must then return the object. While technically you can return |
|
|
1209 | any Perl scalar, you might have to enable the C<enable_nonref> setting to |
|
|
1210 | make that work in all cases, so better return an actual blessed reference. |
|
|
1211 | |
|
|
1212 | As an example, let's implement a C<THAW> function that regenerates the |
|
|
1213 | C<My::Object> from the C<FREEZE> example earlier: |
|
|
1214 | |
|
|
1215 | sub My::Object::THAW { |
|
|
1216 | my ($class, $serialiser, $type, $id) = @_; |
|
|
1217 | |
|
|
1218 | $class->new (type => $type, id => $id) |
|
|
1219 | } |
1087 | |
1220 | |
1088 | |
1221 | |
1089 | =head1 ENCODING/CODESET FLAG NOTES |
1222 | =head1 ENCODING/CODESET FLAG NOTES |
1090 | |
1223 | |
1091 | The interested reader might have seen a number of flags that signify |
1224 | The interested reader might have seen a number of flags that signify |