JSON - JSON (JavaScript Object Notation) encoder/decoder
use JSON; # imports encode_json, decode_json, to_json and from_json.
$json_text = to_json($perl_scalar);
$perl_scalar = from_json($json_text);
# option-acceptable
$json_text = to_json($perl_scalar, {ascii => 1});
$perl_scalar = from_json($json_text, {utf8 => 1});
# OOP
$json = new JSON;
$json_text = $json->encode($perl_scalar);
$perl_scalar = $json->decode($json_text);
# pretty-printing
$json_text = $json->pretty->encode($perl_scalar);
# simple interface
$utf8_encoded_json_text = encode_json $perl_hash_or_arrayref;
$perl_hash_or_arrayref = decode_json $utf8_encoded_json_text;
# If you want to use PP only support features, call with '-support_by_pp'
# When XS unsupported feature is enable, using PP de/encode.
use JSON -support_by_pp;
2.07
************************** CAUTION ******************************** * This is 'JSON module version 2' and there are many differences * * to version 1.xx * * Please check your applications useing old version. * * See to 'INCOMPATIBLE CHANGES TO OLD VERSION' and 'TIPS' * *******************************************************************
To distinguish the module name 'JSON' and the format type JSON, the former is quoted by C<> (its results vary with your using media), and the latter is left just as it is.
Module name : JSON
Format type : JSON
JSON (JavaScript Object Notation) is a simple data format.
See to http://www.json.org/ and RFC4627(http://www.ietf.org/rfc/rfc4627.txt).
This module converts Perl data structures to JSON and vice versa using either JSON::XS or JSON::PP.
JSON::XS is the fastest and most proper JSON module on CPAN which must be compiled and installed in your environment. JSON::PP is a pure-Perl module which is bundled in this distribution and has a strong compatibility to JSON::XS.
This module try to use JSON::XS by default and fail to it, use JSON::PP instead. So its features completely depend on JSON::XS or JSON::PP.
See to BACKEND MODULE DECISION.
Basically see to JSON::XS.
This module (i.e. backend modules) knows how to handle Unicode, and even documents how and when it does so.
Even though there is a limitation, this feature is available since Perl 5.6.
JSON::XS requires Perl 5.8.2 (but works correctly in 5.8.8 or later), so in older versions
JSON sholud call JSON::PP as the backend which can be used since Perl 5.005.
With Perl 5.8.x JSON::PP works, but from 5.8.0 to 5.8.2, because of a Perl side problem, JSON::PP works slower in the versions. And in 5.005, the Unicode handling is not available. See to JSON::PP/UNICODE HANDLING ON PERLS for more information.
See also to JSON::XS/A FEW NOTES ON UNICODE AND PERL.
There is no guessing, no generating of illegal JSON texts by default, and only JSON is accepted as input by default (the latter is a security feature).
See to JSON::XS/FEATURES and JSON::PP/FEATURES.
When you use JSON, JSON tries to use JSON::XS. If this call is fail, it uses
JSON::PP. The required JSON::XS version is 2.01 or later.
The JSON constructor method returns an object inherited from the backend module,
and JSON::XS object is a blessed scaler reference while JSON::PP is a blessed hash
reference.
So, your program should not depend on the backend module, especially returned objects should not be modified.
my $json = JSON->new; # XS or PP?
$json->{stash} = 'this is xs object'; # this code may raise an error!
To check the backend module, there are some methods - backend, is_pp and is_xs.
JSON->backend; # 'JSON::XS' or 'JSON::PP' JSON->backend->is_pp: # 0 or 1 JSON->backend->is_xs: # 1 or 0 $json->is_xs; # 1 or 0 $json->is_pp; # 0 or 1
If you set an enviornment variable PERL_JSON_BACKEND, The calling action will be changed.
These ideas come from DBI::PurePerl mechanism.
example:
BEGIN { $ENV{PERL_JSON_BACKEND} = 'JSON::PP' }
use JSON; # always uses JSON::PP
In future, it may be able to specify another module.
There are big incompatibility between new version (2.00) and old (1.xx).
If you use old JSON 1.xx in your code, please check it.
See to Transition ways from 1.xx to 2.xx.
jsonToObj and objToJson are obsoleted
(but not yet deleted from the source).
If you use these functions in your code, please replace them
with from_json and to_json.
JSON class variables - $JSON::AUTOCONVERT, $JSON::BareKey, etc...
- are not avaliable any longer.
Instead, various features can be used through object methods.
JSON bundles with JSON::PP which can handle JSON more properly than them.
There was JSON::NotString class which represents JSON value true, false, null
and numbers. It was deleted and replaced by JSON::Boolean.
JSON::Boolean represents true and false.
JSON::Boolean does not represent null.
JSON::null returns undef.
JSON makes JSON::XS::Boolean and JSON::PP::Boolean is-a relation
to JSON::Boolean.
JSON::Number is now needless because JSON::XS and JSON::PP have
round-trip integrity.
JSONRPC , JSONRPC::Transport::HTTP
and Apache::JSONRPC are deleted in this distribution.
Instead of them, there is JSON::RPC which supports JSON-RPC protocol version 1.1.
Some documents are copied and modified from JSON::XS/FUNCTIONAL INTERFACE.
encode_json and decode_json are additional functions.
Converts the given Perl data structure to a json string.
This function call is functionally identical to:
$json_text = JSON->new->encode($perl_scalar)
Takes a hash reference as the second.
$json_text = encode_json($perl_scalar, {utf8 => 1, pretty => 1})
equivalent to:
$json_text = JSON->new->utf8(1)->pretty(1)->encode($perl_scalar)
The opposite of to_json: expects a json string and tries
to parse it, returning the resulting reference.
This function call is functionally identical to:
$perl_scalar = JSON->decode($json_text)
Takes a hash reference as the second.
$perl_scalar = from_json($json_text, {utf8 => 1})
equivalent to:
$perl_scalar = JSON->new->utf8(1)->decode($json_text)
Converts the given Perl data structure to a UTF-8 encoded, binary string.
This function call is functionally identical to:
$json_text = JSON->new->utf8->encode($perl_scalar)
The opposite of encode_json: expects an UTF-8 (binary) string and tries
to parse that as an UTF-8 encoded JSON text, returning the resulting
reference.
This function call is functionally identical to:
$perl_scalar = JSON->new->utf8->decode($json_text)
Returns true if the passed scalar represents either JSON::true or
JSON::false, two constants that act like 1 and 0 respectively
and are also used to represent JSON true and false in Perl strings.
See MAPPING, below, for more information on how JSON values are mapped to Perl.
Many methods are available with either JSON::XS or JSON::PP and
when the backend module is JSON::XS, if any JSON::PP specific (i.e. JSON::XS unspported)
method is called, it will warn and be noop.
But If you use JSON passing the optional string -support_by_pp,
it makes a part of those unupported methods available.
This feature is achieved by using JSON::PP in de/encode.
BEING { $ENV{PERL_JSON_BACKEND} = 2 } # with JSON::XS
use JSON -support_by_pp;
my $json = new JSON;
$json->allow_nonref->escape_slash->encode("/");
At this time, the returned object is a JSON::Backend::XS::Supportable
object (re-blessed XS object), and by checking JSON::XS unsupported flags
in de/encoding, can support some unsupported methods - loose, allow_bignum,
allow_barekey, allow_singlequote, escape_slash, as_nonblessed
and indent_length.
When any unsupported methods are not enable, XS de/encode will be
used as is. The switch is achieved by changing the symbolic tables.
-support_by_pp is effective only when the backend module is JSON::XS
and it makes the de/encoding speed down a bit.
See to JSON::PP SUPPORT METHODS.
Rturns a new JSON object inherited from either JSON::XS or JSON::PP
that can be used to de/encode JSON strings.
All boolean flags described below are by default disabled.
The mutators for flags all return the JSON object again and thus calls can be chained:
my $json = JSON->new->utf8->space_after->encode({a => [1,2]})
=> {"a": [1, 2]}
If $enable is true (or missing), then the encode method will not generate characters outside the code range 0..127. Any Unicode characters outside that range will be escaped using either a single \uXXXX or a double \uHHHH\uLLLLL escape sequence, as per RFC4627.
If $enable is false, then the encode method will not escape Unicode characters unless required by the JSON syntax or other flags. This results in a faster and more compact format.
This feature depends on the used Perl version and environment.
See to JSON::PP/UNICODE HANDLING ON PERLS if the backend is PP.
JSON->new->ascii(1)->encode([chr 0x10401]) => ["\ud801\udc01"]
If $enable is true (or missing), then the encode method will encode the resulting JSON text as latin1 (or iso-8859-1), escaping any characters outside the code range 0..255.
If $enable is false, then the encode method will not escape Unicode characters unless required by the JSON syntax or other flags.
JSON->new->latin1->encode (["\x{89}\x{abc}"]
=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
If $enable is true (or missing), then the encode method will encode the JSON result into UTF-8, as required by many protocols, while the decode method expects to be handled an UTF-8-encoded string. Please note that UTF-8-encoded strings do not contain any characters outside the range 0..255, they are thus useful for bytewise/binary I/O.
In future versions, enabling this option might enable autodetection of the UTF-16 and UTF-32 encoding families, as described in RFC4627.
If $enable is false, then the encode method will return the JSON string as a (non-encoded) Unicode string, while decode expects thus a Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs to be done yourself, e.g. using the Encode module.
Example, output UTF-16BE-encoded JSON:
use Encode; $jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
Example, decode UTF-32LE-encoded JSON:
use Encode; $object = JSON::XS->new->decode (decode "UTF-32LE", $jsontext);
See to JSON::PP/UNICODE HANDLING ON PERLS if the backend is PP.
This enables (or disables) all of the indent, space_before and
space_after (and in the future possibly more) flags in one call to
generate the most readable (or most compact) form possible.
Equivalent to:
$json->indent->space_before->space_after
The indent space length is three and JSON::XS cannot change the indent space length.
If $enable is true (or missing), then the encode method will use a multiline
format as output, putting every array member or object/hash key-value pair
into its own line, identing them properly.
If $enable is false, no newlines or indenting will be produced, and the
resulting JSON text is guarenteed not to contain any newlines.
This setting has no effect when decoding JSON texts.
The indent space length is three.
With JSON::PP, you can also access indent_length to change indent space length.
If $enable is true (or missing), then the encode method will add an extra
optional space before the : separating keys from values in JSON objects.
If $enable is false, then the encode method will not add any extra
space at those places.
This setting has no effect when decoding JSON texts.
Example, space_before enabled, space_after and indent disabled:
{"key" :"value"}
If $enable is true (or missing), then the encode method will add an extra
optional space after the : separating keys from values in JSON objects
and extra whitespace after the , separating key-value pairs and array
members.
If $enable is false, then the encode method will not add any extra
space at those places.
This setting has no effect when decoding JSON texts.
Example, space_before and indent disabled, space_after enabled:
{"key": "value"}
If $enable is true (or missing), then decode will accept some
extensions to normal JSON syntax (see below). encode will not be
affected in anyway. Be aware that this option makes you accept invalid
JSON texts as if they were valid!. I suggest only to use this option to
parse application-specific files written by humans (configuration files,
resource files etc.)
If $enable is false (the default), then decode will only accept
valid JSON texts.
Currently accepted extensions are:
JSON separates array elements and key-value pairs with commas. This can be annoying if you write JSON texts manually and want to be able to quickly append elements, so this extension accepts comma at the end of such items not just between them:
[
1,
2, <- this comma not normally allowed
]
{
"k1": "v1",
"k2": "v2", <- this comma not normally allowed
}
Whenever JSON allows whitespace, shell-style comments are additionally allowed. They are terminated by the first carriage-return or line-feed character, after which more white-space and comments are allowed.
[
1, # this comment not allowed in JSON
# neither this one...
]
If $enable is true (or missing), then the encode method will output JSON objects
by sorting their keys. This is adding a comparatively high overhead.
If $enable is false, then the encode method will output key-value
pairs in the order Perl stores them (which will likely change between runs
of the same script).
This option is useful if you want the same data structure to be encoded as the same JSON text (given the same overall settings). If it is disabled, the same hash might be encoded differently even if contains the same data, as key-value pairs have no inherent ordering in Perl.
This setting has no effect when decoding JSON texts.
If $enable is true (or missing), then the encode method can convert a
non-reference into its corresponding string, number or null JSON value,
which is an extension to RFC4627. Likewise, decode will accept those JSON
values instead of croaking.
If $enable is false, then the encode method will croak if it isn't
passed an arrayref or hashref, as JSON texts must either be an object
or array. Likewise, decode will croak if given something that is not a
JSON object or array.
JSON->new->allow_nonref->encode ("Hello, World!")
=> "Hello, World!"
If $enable is true (or missing), then the encode method will not
barf when it encounters a blessed reference. Instead, the value of the
convert_blessed option will decide whether null (convert_blessed
disabled or no TO_JSON method found) or a representation of the
object (convert_blessed enabled and TO_JSON method found) is being
encoded. Has no effect on decode.
If $enable is false (the default), then encode will throw an
exception when it encounters a blessed object.
If $enable is true (or missing), then encode, upon encountering a
blessed object, will check for the availability of the TO_JSON method
on the object's class. If found, it will be called in scalar context
and the resulting scalar will be encoded instead of the object. If no
TO_JSON method is found, the value of allow_blessed will decide what
to do.
The TO_JSON method may safely call die if it wants. If TO_JSON
returns other blessed objects, those will be handled in the same
way. TO_JSON must take care of not causing an endless recursion cycle
(== crash) in this case. The name of TO_JSON was chosen because other
methods called by the Perl core (== not by the user of the object) are
usually in upper case letters and to avoid collisions with the to_json
function or method.
This setting does not yet influence decode in any way.
If $enable is false, then the allow_blessed setting will decide what
to do when a blessed object is found.
If use JSON with -convert_blessed_universally, the UNIVERSAL::TO_JSON
subroutine is defined as the below code:
*UNIVERSAL::TO_JSON = sub {
my $b_obj = B::svref_2object( $_[0] );
return $b_obj->isa('B::HV') ? { %{ $_[0] } }
: $b_obj->isa('B::AV') ? [ @{ $_[0] } ]
: undef
;
}
This will cause that encode method converts simple blessed objects into
JSON objects as non-blessed object.
JSON -convert_blessed_universally; $json->allow_blessed->convert_blessed->encode( $blessed_object )
This feature is experimental and may be removed in the future.
When $coderef is specified, it will be called from decode each
time it decodes a JSON object. The only argument passed to the coderef
is a reference to the newly-created hash. If the code references returns
a single scalar (which need not be a reference), this value
(i.e. a copy of that scalar to avoid aliasing) is inserted into the
deserialised data structure. If it returns an empty list
(NOTE: not undef, which is a valid scalar), the original deserialised
hash will be inserted. This setting can slow down decoding considerably.
When $coderef is omitted or undefined, any existing callback will
be removed and decode will not change the deserialised hash in any
way.
Example, convert all JSON objects into the integer 5:
my $js = JSON->new->filter_json_object (sub { 5 });
# returns [5]
$js->decode ('[{}]'); # the given subroutine takes a hash reference.
# throw an exception because allow_nonref is not enabled
# so a lone 5 is not allowed.
$js->decode ('{"a":1, "b":2}');
Works remotely similar to filter_json_object, but is only called for
JSON objects having a single key named $key.
This $coderef is called before the one specified via
filter_json_object, if any. It gets passed the single value in the JSON
object. If it returns a single value, it will be inserted into the data
structure. If it returns nothing (not even undef but the empty list),
the callback from filter_json_object will be called next, as if no
single-key callback were specified.
If $coderef is omitted or undefined, the corresponding callback will be
disabled. There can only ever be one callback for a given key.
As this callback gets called less often then the filter_json_object
one, decoding speed will not usually suffer as much. Therefore, single-key
objects make excellent targets to serialise Perl objects into, especially
as single-key JSON objects are as close to the type-tagged value concept
as JSON gets (it's basically an ID/VALUE tuple). Of course, JSON does not
support this in any way, so you need to make sure your data never looks
like a serialised Perl hash.
Typical names for the single object key are __class_whatever__, or
$__dollars_are_rarely_used__$ or }ugly_brace_placement, or even
things like __class_md5sum(classname)__, to reduce the risk of clashing
with real hashes.
Example, decode JSON objects of the form { "__widget__" => <id> }
into the corresponding $WIDGET{<id>} object:
# return whatever is in $WIDGET{5}:
JSON
->new
->filter_json_single_key_object (__widget__ => sub {
$WIDGET{ $_[0] }
})
->decode ('{"__widget__": 5')
# this can be used with a TO_JSON method in some "widget" class
# for serialisation to json:
sub WidgetBase::TO_JSON {
my ($self) = @_;
unless ($self->{id}) {
$self->{id} = ..get..some..id..;
$WIDGET{$self->{id}} = $self;
}
{ __widget__ => $self->{id} }
}
With JSON::XS, this flag resizes strings generated by either
encode or decode to their minimum size possible. This can save
memory when your JSON texts are either very very long or you have many
short strings. It will also try to downgrade any strings to octet-form
if possible: perl stores strings internally either in an encoding called
UTF-X or in octet-form. The latter cannot store everything but uses less
space in general (and some buggy Perl or C code might even rely on that
internal representation being used).
With JSON::PP, it is noop about resizing strings but tries
utf8::downgrade to the returned string by encode. See to utf8.
See to JSON::XS/OBJECT-ORIENTED INTERFACE and JSON::PP/METHODS.
Sets the maximum nesting level (default 512) accepted while encoding
or decoding. If the JSON text or Perl data structure has an equal or
higher nesting level then this limit, then the encoder and decoder will
stop and croak at that point.
Nesting level is defined by number of hash- or arrayrefs that the encoder
needs to traverse to reach a given point or the number of { or [
characters without their matching closing parenthesis crossed to reach a
given character in a string.
The argument to max_depth will be rounded up to the next highest power
of two. If no argument is given, the highest possible setting will be
used, which is rarely useful.
This rounding up feature is for JSON::XS internal C structure. To the compatibility, JSON::PP has the same feature.
With JSON::PP, when a large value (100 or more) was set and it de/encodes a deep nested object/text, it may raise a warning 'Deep recursion on subroutin' at the perl runtime phase.
See JSON::XS/SECURITY CONSIDERATIONS for more info on why this is useful.
Set the maximum length a JSON text may have (in bytes) where decoding is
being attempted. The default is 0, meaning no limit. When decode
is called on a string longer then this number of characters it will not
attempt to decode the string but throw an exception. This setting has no
effect on encode (yet).
The argument to max_size will be rounded up to the next highest
power of two (so may be more than requested). If no argument is given, the
limit check will be deactivated (same as when 0 is specified).
This rounding up feature is for JSON::XS internal C structure. To the compatibility, JSON::PP has the same feature.
See JSON::XS/SECURITY CONSIDERATIONS, below, for more info on why this is useful.
When get_max_size returns 1, that means max_size is specified with 0,
while property('max_size') returns 0.
undef) become JSON null values. Neither true
nor false values will be generated.
The opposite of encode: expects a JSON text and tries to parse it,
returning the resulting simple scalar or reference. Croaks on error.
JSON numbers and strings become simple Perl scalars. JSON arrays become
Perl arrayrefs and JSON objects become Perl hashrefs. true becomes
1, false becomes 0 and null becomes undef.
This works like the decode method, but instead of raising an exception
when there is trailing garbage after the first JSON object, it will
silently stop parsing there and return the number of characters consumed
so far.
JSON->new->decode_prefix ("[1] the tail")
=> ([], 3)
Returns a boolean value about above some properties.
The enable properties are ascii, latin1, utf8,
indent,space_before, space_after, relaxed, canonical,
allow_nonref, allow_blessed, convert_blessed, shrink
get_max_depth and get_max_size.
$boolean = $json->property('utf8');
=> 0
$json->utf8;
$boolean = $json->property('utf8');
=> 1
Sets the propery with a given boolean value.
$json->property(utf8 => 1);
The enable properties are ascii, latin1, utf8,
indent,space_before, space_after, relaxed, canonical,
allow_nonref, allow_blessed, convert_blessed, shrink
get_max_depth and get_max_size.
The below methods are JSON::PP own methods, so when JSON works
with JSON::PP (i.e. the created object is a JSON::PP object), available.
See to JSON::PP/JSON::PP OWN METHODS in detail.
If you use JSON with additonal -support_by_pp, some methods
are available even with JSON::XS. See to USE PP FEATURES EVEN THOUGH XS BACKEND.
BEING { $ENV{PERL_JSON_BACKEND} = 'JSON::XS' }
use JSON -support_by_pp;
my $json = new JSON;
$json->allow_nonref->escape_slash->encode("/");
# functional interfaces too.
print to_json(["/"], {escape_slash => 1});
print from_json('["foo"]', {utf8 => 1});
If you do not want to all functions but -support_by_pp,
use -no_export.
use JSON -support_by_pp, -no_export; # functional interfaces are not exported.
If $enable is true (or missing), then decode will accept
any JSON strings quoted by single quotations that are invalid JSON
format.
$json->allow_singlequote->decode({"foo":'bar'});
$json->allow_singlequote->decode({'foo':"bar"});
$json->allow_singlequote->decode({'foo':'bar'});
As same as the relaxed option, this option may be used to parse
application-specific files written by humans.
If $enable is true (or missing), then decode will accept
bare keys of JSON object that are invalid JSON format.
As same as the relaxed option, this option may be used to parse
application-specific files written by humans.
$json->allow_barekey->decode({foo:"bar"});
If $enable is true (or missing), then decode will convert
the big integer Perl cannot handle as integer into a Math::BigInt
object and convert a floating number (any) into a Math::BigFloat.
On the contary, encode converts Math::BigInt objects and Math::BigFloat
objects into JSON numbers with allow_blessed enable.
$json->allow_nonref->allow_blessed->allow_bignum;
$bigfloat = $json->decode('2.000000000000000000000000001');
print $json->encode($bigfloat);
# => 2.000000000000000000000000001
See to MAPPING aboout the conversion of JSON number.
The unescaped [\x00-\x1f\x22\x2f\x5c] strings are invalid in JSON strings
and the module doesn't allow to decode to these (except for \x2f).
If $enable is true (or missing), then decode will accept these
unescaped strings.
$json->loose->decode(qq|["abc
def"]|);
See to JSON::PP/JSON::PP OWN METHODS.
According to JSON Grammar, slash (U+002F) is escaped. But by default JSON backend modules encode strings without escaping slash.
If $enable is true (or missing), then encode will escape slashes.
(OBSOLETED)
If $enable is true (or missing), then encode will convert
a blessed hash reference or a blessed array reference (contains
other blessed references) into JSON members and arrays.
This feature is effective only when allow_blessed is enable.
Since JSON 2.07, there is the convert_blessed_universally mode.
(This switch is experimental too.)
JSON -convert_blessed_universally; $json->allow_blessed->convert_blessed->encode( $blessed_object )
See to convert_blessed.
If $function_name or $subroutine_ref are set, its sort routine are used.
$js = $pc->sort_by(sub { $JSON::PP::a cmp $JSON::PP::b })->encode($obj);
# is($js, q|{"a":1,"b":2,"c":3,"d":4,"e":5,"f":6,"g":7,"h":8,"i":9}|);
$js = $pc->sort_by('own_sort')->encode($obj);
# is($js, q|{"a":1,"b":2,"c":3,"d":4,"e":5,"f":6,"g":7,"h":8,"i":9}|);
sub JSON::PP::own_sort { $JSON::PP::a cmp $JSON::PP::b }
As the sorting routine runs in the JSON::PP scope, the given
subroutine name and the special variables $a, $b will begin
with 'JSON::PP::'.
If $integer is set, then the effect is same as canonical on.
See to JSON::PP/JSON::PP OWN METHODS.
This section is copied from JSON::XS and modified to JSON.
JSON::XS and JSON::PP mapping mechanisms are almost equivalent.
See to JSON::XS/MAPPING.
A JSON number becomes either an integer, numeric (floating point) or string scalar in perl, depending on its range and any fractional parts. On the Perl level, there is no difference between those as Perl handles all the conversion details, but an integer may take slightly less memory and might represent more values exactly than (floating point) numbers.
If the number consists of digits only, JSON will try to represent
it as an integer value. If that fails, it will try to represent it as
a numeric (floating point) value if that is possible without loss of
precision. Otherwise it will preserve the number as a string value.
Numbers containing a fractional or exponential part will always be represented as numeric (floating point) values, possibly at a loss of precision.
This might create round-tripping problems as numbers might become strings, but as Perl is typeless there is no other way to do it.
With JSON::PP, the big integers and the numeric can be optionally converted into Math::BigInt and Math::BigFloat objects.
These JSON atoms become JSON::true and JSON::false,
respectively. They are overloaded to act almost exactly like the numbers
1 and 0. You can check wether a scalar is a JSON boolean by using
the JSON::is_bool function.
If JSON::true and JSON::false are used as strings or compared as strings,
they represent as true and false respectively.
print JSON::true . "\n";
=> true
print JSON::true + 1;
=> 1
ok(JSON::true eq 'true');
ok(JSON::true eq '1');
ok(JSON::true == 1);
JSON will install these missing overloading features to the backend modules.
A JSON null atom becomes undef in Perl.
JSON::null returns unddef.
The mapping from Perl to JSON is slightly more difficult, as Perl is a truly typeless language, so we can only guess which JSON type is meant by a Perl value.
Perl hash references become JSON objects. As there is no inherent ordering
in hash keys (or JSON objects), they will usually be encoded in a
pseudo-random order that can change between runs of the same program but
stays generally the same within a single run of a program. JSON
optionally sort the hash keys (determined by the canonical flag), so
the same datastructure will serialise to the same JSON text (given same
settings and version of JSON::XS), but this incurs a runtime overhead
and is only rarely useful, e.g. when you want to compare some JSON text
against another for equality.
In future, the ordered object feature will be added to JSON::PP using tie mechanism.
Other unblessed references are generally not allowed and will cause an
exception to be thrown, except for references to the integers 0 and
1, which get turned into false and true atoms in JSON. You can
also use JSON::false and JSON::true to improve readability.
to_json [\0,JSON::true] # yields [false,true]
These special values become JSON true and JSON false values,
respectively. You can also use \1 and \0 directly if you want.
JSON::null returns undef.
Blessed objects are not allowed. JSON currently tries to encode their underlying representation (hash- or arrayref), but this behaviour might change in future versions.
With convert_blessed_universally mode, encode converts blessed
hash references or blessed array references (contains other blessed references)
into JSON members and arrays.
use JSON -convert_blessed_universally; JSON->new->allow_blessed->convert_blessed->encode( $blessed_object );
See to convert_blessed.
Simple Perl scalars (any scalar that is not a reference) are the most difficult objects to encode: JSON::XS and JSON::PP will encode undefined scalars as JSON null value, scalars that have last been used in a string context before encoding as JSON strings and anything else as number value:
# dump as number encode_json [2] # yields [2] encode_json [-3.0e17] # yields [-3e+17] my $value = 5; encode_json [$value] # yields [5] # used as string, so dump as string print $value; encode_json [$value] # yields ["5"] # undef becomes null encode_json [undef] # yields [null]
You can force the type to be a string by stringifying it:
my $x = 3.1; # some variable containing a number "$x"; # stringified $x .= ""; # another, more awkward way to stringify print $x; # perl does it for you, too, quite often
You can force the type to be a number by numifying it:
my $x = "3"; # some variable containing a string $x += 0; # numify it, ensuring it will be dumped as a number $x *= 1; # same thing, the choise is yours.
You can not currently output JSON booleans or force the type in other, less obscure, ways. Tell me if you need this capability.
allow_bignum is enable, then
encode converts Math::BigInt objects and Math::BigFloat
objects into JSON numbers.
You should set suport_by_pp mode firstly, because
it is always successful for the below codes even with JSON::XS.
use JSON -support_by_pp;
from_json($json_text);
to_json($perl_scalar);
$flags = {allow_barekey => 1, allow_singlequote => 1};
from_json($json_text, $flags);
equivalent to:
$JSON::BareKey = 1; $JSON::QuotApos = 1; jsonToObj($json_text);
$flags = {allow_blessed => 1, allow_barekey => 1};
to_json($perl_scalar, $flags);
equivalent to:
$JSON::BareKey = 1; objToJson($perl_scalar);
$json->decode($json_text);
$json->encode($perl_scalar);
If indent is enable, that menas $JSON::Pretty flag set. And
$JSON::Delimiter was substituted by space_before and space_after.
In conclusion:
$json->indent->space_before->space_after;
Equivalent to:
$json->pretty;
To change indent length, use indent_length.
(Only with JSON::PP, if -support_by_pp is not used.)
$json->pretty->indent_length(2)->encode($perl_scalar);
(Only with JSON::PP, if -support_by_pp is not used.)
$json->allow_barekey->decode($json_text)
-convert_blessed_universally. See to convert_blessed.
(Only with JSON::PP, if -support_by_pp is not used.)
$json->allow_singlequote->decode($json_text)
JSON does not make such a invalid JSON string any longer.
$json->canonical->encode($perl_scalar)
This is the ascii sort.
If you want to use with your own sort routine, check the sort_by method.
(Only with JSON::PP, even if -support_by_pp is used currently.)
$json->sort_by($sort_routine_ref)->encode($perl_scalar)
$json->sort_by(sub { $JSON::PP::a <=> $JSON::PP::b })->encode($perl_scalar)
Can't access $a and $b but $JSON::PP::a and $JSON::PP::b.
Needless because JSON (either with JSON::XS or JSON::PP) sets the UTF8 flag on properly.
# With UTF8-flagged strings
$json->allow_nonref;
$str = chr(1000); # UTF8-flagged
$json_text = $json->utf8(0)->encode($str);
utf8::is_utf8($json_text);
# true
$json_text = $json->utf8(1)->encode($str);
utf8::is_utf8($json_text);
# false
$str = '"' . chr(1000) . '"'; # UTF8-flagged
$perl_scalar = $json->utf8(0)->decode($str);
utf8::is_utf8($perl_scalar);
# true
$perl_scalar = $json->utf8(1)->decode($str);
# died because of 'Wide character in subroutine'
If you want to make a string in a scalar returned by decode UTF8-flagged off,
utf8::encode($perl_arrayref->[0]);
utf8::encode($perl_hashref->{key});
This option was deleted.
Instead of it, if a givien blessed object has the TO_JSON method,
TO_JSON will be executed with convert_blessed.
$json->convert_blessed->encode($bleesed_hashref_or_arrayref) # if need, call allow_blessed
Note that it was toJson in old version, but now not toJson but TO_JSON.
No test with JSON::PP. If with JSON::XS, See to JSON::XS/THREADS.
Please report bugs relevant to JSON to <makamaka[at]cpan.org>.
Most of the document is copied and modified from JSON::XS doc.
RFC4627(http://www.ietf.org/rfc/rfc4627.txt)
Makamaka Hannyaharamitu, <makamaka[at]cpan.org>
JSON::XS was written by Marc Lehmann <schmorp[at]schmorp.de>
The relese of this new version owes to the courtesy of Marc Lehmann.
Copyright 2005-2008 by Makamaka Hannyaharamitu
This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.