… | |
… | |
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; |
… | |
… | |
986 | |
986 | |
987 | =item null |
987 | =item null |
988 | |
988 | |
989 | A JSON null atom becomes C<undef> in Perl. |
989 | A JSON null atom becomes C<undef> in Perl. |
990 | |
990 | |
|
|
991 | =item shell-style comments (C<< # I<text> >>) |
|
|
992 | |
|
|
993 | As a nonstandard extension to the JSON syntax that is enabled by the |
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994 | C<relaxed> setting, shell-style comments are allowed. They can start |
|
|
995 | anywhere outside strings and go till the end of the line. |
|
|
996 | |
|
|
997 | =item tagged values (C<< (I<tag>)I<value> >>). |
|
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998 | |
|
|
999 | Another nonstandard extension to the JSON syntax, enabled with the |
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|
1000 | C<allow_tags> setting, are tagged values. In this implementation, the |
|
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1001 | I<tag> must be a perl package/class name encoded as a JSON string, and the |
|
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1002 | I<value> must be a JSON array encoding optional constructor arguments. |
|
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1003 | |
|
|
1004 | See "OBJECT SERIALISATION", below, for details. |
|
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1005 | |
991 | =back |
1006 | =back |
992 | |
1007 | |
993 | |
1008 | |
994 | =head2 PERL -> JSON |
1009 | =head2 PERL -> JSON |
995 | |
1010 | |
… | |
… | |
1032 | and JSON false values, respectively. You can also use C<\1> and C<\0> |
1047 | and JSON false values, respectively. You can also use C<\1> and C<\0> |
1033 | directly if you want. |
1048 | directly if you want. |
1034 | |
1049 | |
1035 | =item blessed objects |
1050 | =item blessed objects |
1036 | |
1051 | |
1037 | Blessed objects are not directly representable in JSON. See the |
1052 | 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 |
1053 | allows various ways of handling objects. See "OBJECT SERIALISATION", |
1039 | how to deal with this: basically, you can choose between throwing an |
1054 | below, for details. |
1040 | exception, encoding the reference as if it weren't blessed, or provide |
|
|
1041 | your own serialiser method. |
|
|
1042 | |
1055 | |
1043 | =item simple scalars |
1056 | =item simple scalars |
1044 | |
1057 | |
1045 | Simple Perl scalars (any scalar that is not a reference) are the most |
1058 | 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 |
1059 | difficult objects to encode: JSON::XS will encode undefined scalars as |
… | |
… | |
1082 | extensions to the floating point numbers of your platform, such as |
1095 | 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 |
1096 | infinities or NaN's - these cannot be represented in JSON, and it is an |
1084 | error to pass those in. |
1097 | error to pass those in. |
1085 | |
1098 | |
1086 | =back |
1099 | =back |
|
|
1100 | |
|
|
1101 | =head2 OBJECT SERIALISATION |
|
|
1102 | |
|
|
1103 | As JSON cannot directly represent Perl objects, you have to choose between |
|
|
1104 | a pure JSON representation (without the ability to deserialise the object |
|
|
1105 | automatically again), and a nonstandard extension to the JSON syntax, |
|
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1106 | tagged values. |
|
|
1107 | |
|
|
1108 | =head3 SERIALISATION |
|
|
1109 | |
|
|
1110 | What happens when C<JSON::XS> encounters a Perl object depends on the |
|
|
1111 | C<allow_blessed>, C<convert_blessed> and C<allow_tags> settings, which are |
|
|
1112 | used in this order: |
|
|
1113 | |
|
|
1114 | =over 4 |
|
|
1115 | |
|
|
1116 | =item 1. C<allow_tags> is enabled and object has a C<FREEZE> method. |
|
|
1117 | |
|
|
1118 | In this case, C<JSON::XS> uses the L<Types::Serialiser> object |
|
|
1119 | serialisation protocol to create a tagged JSON value, using a nonstandard |
|
|
1120 | extension to the JSON syntax. |
|
|
1121 | |
|
|
1122 | This works by invoking the C<FREEZE> method on the object, with the first |
|
|
1123 | argument being the object to serialise, and the second argument being the |
|
|
1124 | constant string C<JSON> to distinguish it from other serialisers. |
|
|
1125 | |
|
|
1126 | The C<FREEZE> method can return any number of values (i.e. zero or |
|
|
1127 | more). These values and the paclkage/classname of the object will then be |
|
|
1128 | encoded as a tagged JSON value in the following format: |
|
|
1129 | |
|
|
1130 | ("classname")[FREEZE return values...] |
|
|
1131 | |
|
|
1132 | For example, the hypothetical C<My::Object> C<FREEZE> method might use the |
|
|
1133 | objects C<type> and C<id> members to encode the object: |
|
|
1134 | |
|
|
1135 | sub My::Object::FREEZE { |
|
|
1136 | my ($self, $serialiser) = @_; |
|
|
1137 | |
|
|
1138 | ($self->{type}, $self->{id}) |
|
|
1139 | } |
|
|
1140 | |
|
|
1141 | =item 2. C<convert_blessed> is enabled and object has a C<TO_JSON> method. |
|
|
1142 | |
|
|
1143 | In this case, the C<TO_JSON> method of the object is invoked in scalar |
|
|
1144 | context. It must return a single scalar that can be directly encoded into |
|
|
1145 | JSON. This scalar replaces the object in the JSON text. |
|
|
1146 | |
|
|
1147 | For example, the following C<TO_JSON> method will convert all L<URI> |
|
|
1148 | objects to JSON strings when serialised. The fatc that these values |
|
|
1149 | originally were L<URI> objects is lost. |
|
|
1150 | |
|
|
1151 | sub URI::TO_JSON { |
|
|
1152 | my ($uri) = @_; |
|
|
1153 | $uri->as_string |
|
|
1154 | } |
|
|
1155 | |
|
|
1156 | =item 3. C<allow_blessed> is enabled. |
|
|
1157 | |
|
|
1158 | The object will be serialised as a JSON null value. |
|
|
1159 | |
|
|
1160 | =item 4. none of the above |
|
|
1161 | |
|
|
1162 | If none of the settings are enabled or the respective methods are missing, |
|
|
1163 | C<JSON::XS> throws an exception. |
|
|
1164 | |
|
|
1165 | =back |
|
|
1166 | |
|
|
1167 | =head3 DESERIALISATION |
|
|
1168 | |
|
|
1169 | For deserialisation there are only two cases to consider: either |
|
|
1170 | nonstandard tagging was used, in which case C<allow_tags> decides, |
|
|
1171 | or objects cannot be automatically be deserialised, in which |
|
|
1172 | case you can use postprocessing or the C<filter_json_object> or |
|
|
1173 | C<filter_json_single_key_object> callbacks to get some real objects our of |
|
|
1174 | your JSON. |
|
|
1175 | |
|
|
1176 | This section only considers the tagged value case: I a tagged JSON object |
|
|
1177 | is encountered during decoding and C<allow_tags> is disabled, a parse |
|
|
1178 | error will result (as if tagged values were not part of the grammar). |
|
|
1179 | |
|
|
1180 | If C<allow_tags> is enabled, C<JSON::XS> will look up the C<THAW> method |
|
|
1181 | of the package/classname used during serialisation. If there is no such |
|
|
1182 | method, the decoding will fail with an error. |
|
|
1183 | |
|
|
1184 | Otherwise, the C<THAW> method is invoked with the classname as first |
|
|
1185 | argument, the constant string C<JSON> as second argument, and all the |
|
|
1186 | values from the JSON array (the values originally returned by the |
|
|
1187 | C<FREEZE> method) as remaining arguments. |
|
|
1188 | |
|
|
1189 | The method must then return the object. While technically you can return |
|
|
1190 | any Perl scalar, you might have to enable the C<enable_nonref> setting to |
|
|
1191 | make that work in all cases, so better return an actual blessed reference. |
|
|
1192 | |
|
|
1193 | As an example, let's implement a C<THAW> function that regenerates the |
|
|
1194 | C<My::Object> from the C<FREEZE> example earlier: |
|
|
1195 | |
|
|
1196 | sub My::Object::THAW { |
|
|
1197 | my ($class, $serialiser, $type, $id) = @_; |
|
|
1198 | |
|
|
1199 | $class->new (type => $type, id => $id) |
|
|
1200 | } |
1087 | |
1201 | |
1088 | |
1202 | |
1089 | =head1 ENCODING/CODESET FLAG NOTES |
1203 | =head1 ENCODING/CODESET FLAG NOTES |
1090 | |
1204 | |
1091 | The interested reader might have seen a number of flags that signify |
1205 | The interested reader might have seen a number of flags that signify |