JSON version 2.06
=================
INSTALLATION
To install this module type the following:
perl Makefile.PL
make
make test
make install
NAME
JSON - JSON (JavaScript Object Notation) encoder/decoder
SYNOPSIS
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;
VERSION
2.07
DESCRIPTION
************************** 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".
FEATURES
Basically see to JSON::XS.
* correct unicode handling
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 "UNICODE
HANDLING ON PERLS" in JSON::PP for more information.
See also to "A FEW NOTES ON UNICODE AND PERL" in JSON::XS.
* round-trip integrity
When you serialise a perl data structure using only datatypes
supported by JSON, the deserialised data structure is identical on
the Perl level. (e.g. the string "2.0" doesn't suddenly become "2"
just because it looks like a number).
* strict checking of JSON correctness
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 "FEATURES" in JSON::XS and "FEATURES" in JSON::PP.
* fast
With JSON::XS, compared to other JSON modules, this module compares
favourably in terms of speed, too.
* simple to use
This module has both a simple functional interface as well as an OO
interface.
* reasonably versatile output formats
You can choose between the most compact guaranteed single-line
format possible (nice for simple line-based protocols), a pure-ascii
format (for when your transport is not 8-bit clean, still supports
the whole Unicode range), or a pretty-printed format (for when you
want to read that stuff). Or you can combine those features in
whatever way you like.
BACKEND MODULE DECISION
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.
PERL_JSON_BACKEND = 0 or PERL_JSON_BACKEND = 'JSON::PP'
Always use JSON::PP
PERL_JSON_BACKEND == 1 or PERL_JSON_BACKEND = 'JSON::XS,JSON::PP'
(The default) Use compiled JSON::XS if it is properly compiled &
installed, otherwise use JSON::PP.
PERL_JSON_BACKEND == 2 or PERL_JSON_BACKEND = 'JSON::XS'
Always use compiled JSON::XS, die if it isn't properly compiled &
installed.
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.
INCOMPATIBLE CHANGES TO OLD VERSION
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.
Non Perl-style name "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".
Global variables are no longer available.
"JSON" class variables - $JSON::AUTOCONVERT, $JSON::BareKey, etc...
- are not avaliable any longer. Instead, various features can be
used through object methods.
Package JSON::Converter and JSON::Parser are deleted.
Now "JSON" bundles with JSON::PP which can handle JSON more properly
than them.
Package JSON::NotString is deleted.
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.
function JSON::Number is obsoleted.
"JSON::Number" is now needless because JSON::XS and JSON::PP have
round-trip integrity.
JSONRPC modules are deleted.
Perl implementation of JSON-RPC protocol - "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.
FUNCTIONAL INTERFACE
Some documents are copied and modified from "FUNCTIONAL INTERFACE" in
JSON::XS. "encode_json" and "decode_json" are additional functions.
$json_text = to_json($perl_scalar)
Converts the given Perl data structure to a json string.
This function call is functionally identical to:
$json_text = JSON->new->encode($perl_scalar)
$json_text = to_json($perl_scalar, $flag_hashref)
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)
$perl_scalar = from_json($json_text)
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)
$perl_scalar = from_json($json_text, $flag_hashref)
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)
$json_text = encode_json $perl_scalar
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)
$perl_scalar = decode_json $json_text
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)
$is_boolean = JSON::is_bool($scalar)
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.
USE PP FEATURES EVEN THOUGH XS BACKEND
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".
COMMON OBJECT-ORIENTED INTERFACE
$json = new JSON
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]}
$json = $json->ascii([$enable])
$enabled = $json->get_ascii
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 "UNICODE HANDLING ON PERLS" in JSON::PP if the backend is PP.
JSON->new->ascii(1)->encode([chr 0x10401])
=> ["\ud801\udc01"]
$json = $json->latin1([$enable])
$enabled = $json->get_latin1
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)
$json = $json->utf8([$enable])
$enabled = $json->get_utf8
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 "UNICODE HANDLING ON PERLS" in JSON::PP if the backend is PP.
$json = $json->pretty([$enable])
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.
$json = $json->indent([$enable])
$enabled = $json->get_indent
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.
$json = $json->space_before([$enable])
$enabled = $json->get_space_before
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"}
$json = $json->space_after([$enable])
$enabled = $json->get_space_after
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"}
$json = $json->relaxed([$enable])
$enabled = $json->get_relaxed
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:
* list items can have an end-comma
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
}
* shell-style '#'-comments
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...
]
$json = $json->canonical([$enable])
$enabled = $json->get_canonical
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.
$json = $json->allow_nonref([$enable])
$enabled = $json->get_allow_nonref
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!"
$json = $json->allow_blessed([$enable])
$enabled = $json->get_allow_blessed
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.
$json = $json->convert_blessed([$enable])
$enabled = $json->get_convert_blessed
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.
$json = $json->filter_json_object([$coderef])
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}');
$json = $json->filter_json_single_key_object($key [=> $coderef])
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} }
}
$json = $json->shrink([$enable])
$enabled = $json->get_shrink
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 "OBJECT-ORIENTED INTERFACE" in JSON::XS and "METHODS" in
JSON::PP.
$json = $json->max_depth([$maximum_nesting_depth])
$max_depth = $json->get_max_depth
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 "SECURITY CONSIDERATIONS" in JSON::XS for more info on why this
is useful.
$json = $json->max_size([$maximum_string_size])
$max_size = $json->get_max_size
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 "SECURITY CONSIDERATIONS" in JSON::XS, 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.
$json_text = $json->encode($perl_scalar)
Converts the given Perl data structure (a simple scalar or a
reference to a hash or array) to its JSON representation. Simple
scalars will be converted into JSON string or number sequences,
while references to arrays become JSON arrays and references to
hashes become JSON objects. Undefined Perl values (e.g. "undef")
become JSON "null" values. Neither "true" nor "false" values will be
generated.
$perl_scalar = $json->decode($json_text)
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".
($perl_scalar, $characters) = $json->decode_prefix($json_text)
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)
See to "OBJECT-ORIENTED INTERFACE" in JSON::XS
$boolean = $json->property($property_name)
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
$json = $json->property($property_name => $boolean);
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".
$flag_hashref = $json->property();
Returns all the above properties as a hash reference.
JSON::PP SUPPORT METHODS
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 OWN METHODS" in JSON::PP 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.
$json = $json->allow_singlequote([$enable])
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.
$json = $json->allow_barekey([$enable])
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"});
$json = $json->allow_bignum([$enable])
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.
$json = $json->loose([$enable])
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 OWN METHODS" in JSON::PP.
$json = $json->escape_slash([$enable])
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.
$json = $json->as_nonblessed
(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".
$json = $json->indent_length($length)
With JSON::XS, The indent space length is 3 and cannot be changed.
With JSON::PP, it sets the indent space length with the given
$length. The default is 3. The acceptable range is 0 to 15.
$json = $json->sort_by($function_name)
$json = $json->sort_by($subroutine_ref)
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 OWN METHODS" in JSON::PP.
MAPPING
This section is copied from JSON::XS and modified to "JSON". JSON::XS
and JSON::PP mapping mechanisms are almost equivalent.
See to "MAPPING" in JSON::XS.
JSON -> PERL
object
A JSON object becomes a reference to a hash in Perl. No ordering of
object keys is preserved (JSON does not preserver object key
ordering itself).
array
A JSON array becomes a reference to an array in Perl.
string
A JSON string becomes a string scalar in Perl - Unicode codepoints
in JSON are represented by the same codepoints in the Perl string,
so no manual decoding is necessary.
number
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.
true, false
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.
null
A JSON null atom becomes "undef" in Perl.
"JSON::null" returns "unddef".
PERL -> JSON
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.
hash references
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.
array references
Perl array references become JSON arrays.
other references
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]
JSON::true, JSON::false, JSON::null
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
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 scalars
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
$x *= 1; # same thing, the choise is yours.
You can not currently output JSON booleans or force the type in
other, less obscure, ways. Tell me if you need this capability.
Big Number
With JSON::PP as the backend, if "allow_bignum" is enable, then
"encode" converts "Math::BigInt" objects and "Math::BigFloat"
objects into JSON numbers.
TIPS
Transition ways from 1.xx to 2.xx.
You should set "suport_by_pp" mode firstly, because it is always
successful for the below codes even with JSON::XS.
use JSON -support_by_pp;
Exported jsonToObj (simple)
from_json($json_text);
Exported objToJson (simple)
to_json($perl_scalar);
Exported jsonToObj (advanced)
$flags = {allow_barekey => 1, allow_singlequote => 1};
from_json($json_text, $flags);
equivalent to:
$JSON::BareKey = 1;
$JSON::QuotApos = 1;
jsonToObj($json_text);
Exported objToJson (advanced)
$flags = {allow_blessed => 1, allow_barekey => 1};
to_json($perl_scalar, $flags);
equivalent to:
$JSON::BareKey = 1;
objToJson($perl_scalar);
jsonToObj as object method
$json->decode($json_text);
objToJson as object method
$json->encode($perl_scalar);
$JSON::Pretty, $JSON::Indent, $JSON::Delimiter
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);
$JSON::BareKey
(Only with JSON::PP, if "-support_by_pp" is not used.)
$json->allow_barekey->decode($json_text)
$JSON::ConvBlessed
use "-convert_blessed_universally". See to "convert_blessed".
$JSON::QuotApos
(Only with JSON::PP, if "-support_by_pp" is not used.)
$json->allow_singlequote->decode($json_text)
$JSON::SingleQuote
Disable. "JSON" does not make such a invalid JSON string any longer.
$JSON::KeySort
$json->canonical->encode($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.
$JSON::AUTOCONVERT
Needless. It has the round-trip integrity.
$JSON::UTF8
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});
See to "A FEW NOTES ON UNICODE AND PERL" in JSON::XS.
$JSON::UnMapping
Disable. See to MAPPING.
$JSON::SelfConvert
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".
TODO
More tests
THREADS
No test with JSON::PP. If with JSON::XS, See to "THREADS" in JSON::XS.
BUGS
Please report bugs relevant to "JSON" to <makamaka[at]cpan.org>.
SEE ALSO
Most of the document is copied and modified from JSON::XS doc.
JSON::XS, JSON::PP
"RFC4627"(<http://www.ietf.org/rfc/rfc4627.txt>)
AUTHOR
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 AND LICENSE
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.