JSON::PP
- NAME
- SYNOPSIS
- VERSION
- NOTE
- DESCRIPTION
- FUNCTIONAL INTERFACE
- HOW DO I DECODE A DATA FROM OUTER AND ENCODE TO OUTER
- METHODS
- new
- ascii
- latin1
- utf8
- pretty
- indent
- space_before
- space_after
- relaxed
- canonical
- allow_nonref
- allow_unknown
- allow_blessed
- convert_blessed
- filter_json_object
- filter_json_single_key_object
- shrink
- max_depth
- max_size
- encode
- decode
- decode_prefix
- INCREMENTAL PARSING
- JSON::PP OWN METHODS
- INTERNAL
- MAPPING
- UNICODE HANDLING ON PERLS
- TODO
- SEE ALSO
- AUTHOR
- COPYRIGHT AND LICENSE
NAME
JSON::PP - JSON::XS compatible pure-Perl module.
SYNOPSIS
- use JSON::PP;
- # exported functions, they croak on error
- # and expect/generate UTF-8
- $utf8_encoded_json_text = encode_json $perl_hash_or_arrayref;
- $perl_hash_or_arrayref = decode_json $utf8_encoded_json_text;
- # OO-interface
- $coder = JSON::PP->new->ascii->pretty->allow_nonref;
- $json_text = $json->encode( $perl_scalar );
- $perl_scalar = $json->decode( $json_text );
- $pretty_printed = $json->pretty->encode( $perl_scalar ); # pretty-printing
- # Note that JSON version 2.0 and above will automatically use
- # JSON::XS or JSON::PP, so you should be able to just:
- use JSON;
VERSION
- 2.27300
JSON::XS 2.27 (~2.30) compatible.
NOTE
JSON::PP had been inculded in JSON distribution (CPAN module). It was a perl core module in Perl 5.14.
DESCRIPTION
This module is JSON::XS compatible pure Perl module. (Perl 5.8 or later is recommended)
JSON::XS is the fastest and most proper JSON module on CPAN. It is written by Marc Lehmann in C, so must be compiled and installed in the used environment.
JSON::PP is a pure-Perl module and has compatibility to JSON::XS.
FEATURES
- correct unicode handling
This module knows how to handle Unicode (depending on Perl version).
See to A FEW NOTES ON UNICODE AND PERL in JSON::XS and UNICODE HANDLING ON PERLS.
- round-trip integrity
When you serialise a perl data structure using only data types supported by JSON and Perl, 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). There are minor exceptions to this, read the MAPPING section below to learn about those.
- 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). But when some options are set, loose chcking features are available.
FUNCTIONAL INTERFACE
Some documents are copied and modified from FUNCTIONAL INTERFACE in JSON::XS.
encode_json
- $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:
- $json_text = JSON::PP->new->utf8->encode($perl_scalar)
decode_json
- $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:
- $perl_scalar = JSON::PP->new->utf8->decode($json_text)
JSON::PP::is_bool
- $is_boolean = JSON::PP::is_bool($scalar)
Returns true if the passed scalar represents either JSON::PP::true or
JSON::PP::false, two constants that act like 1
and
respectively
and are also used to represent JSON
true
and false
in Perl strings.
JSON::PP::true
Returns JSON true value which is blessed object.
It isa
JSON::PP::Boolean object.
JSON::PP::false
Returns JSON false value which is blessed object.
It isa
JSON::PP::Boolean object.
JSON::PP::null
Returns undef
.
See MAPPING, below, for more information on how JSON values are mapped to Perl.
HOW DO I DECODE A DATA FROM OUTER AND ENCODE TO OUTER
This section supposes that your perl vresion is 5.8 or later.
If you know a JSON text from an outer world - a network, a file content, and so on,
is encoded in UTF-8, you should use decode_json
or JSON
module object
with utf8
enable. And the decoded result will contain UNICODE characters.
If an outer data is not encoded in UTF-8, firstly you should decode
it.
In this case, $unicode_json_text
is of course UNICODE string.
So you cannot use decode_json
nor JSON
module object with utf8
enable.
Instead of them, you use JSON
module object with utf8
disable.
- $perl_scalar = $json->utf8(0)->decode( $unicode_json_text );
Or encode 'utf8'
and decode_json
:
- $perl_scalar = decode_json( encode( 'utf8', $unicode_json_text ) );
- # this way is not efficient.
And now, you want to convert your $perl_scalar
into JSON data and
send it to an outer world - a network or a file content, and so on.
Your data usually contains UNICODE strings and you want the converted data to be encoded
in UTF-8, you should use encode_json
or JSON
module object with utf8
enable.
If $perl_scalar
does not contain UNICODE but $encoding
-encoded strings
for some reason, then its characters are regarded as latin1 for perl
(because it does not concern with your $encoding).
You cannot use encode_json
nor JSON
module object with utf8
enable.
Instead of them, you use JSON
module object with utf8
disable.
Note that the resulted text is a UNICODE string but no problem to print it.
- # $perl_scalar contains $encoding encoded string values
- $unicode_json_text = $json->utf8(0)->encode( $perl_scalar );
- # $unicode_json_text consists of characters less than 0x100
- print $unicode_json_text;
Or decode $encoding
all string values and encode_json
:
- $perl_scalar->{ foo } = decode( $encoding, $perl_scalar->{ foo } );
- # ... do it to each string values, then encode_json
- $json_text = encode_json( $perl_scalar );
This method is a proper way but probably not efficient.
See to Encode, perluniintro.
METHODS
Basically, check to JSON or JSON::XS.
new
- $json = JSON::PP->new
Rturns a new JSON::PP object 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::PP->new->utf8->space_after->encode({a => [1,2]})
- => {"a": [1, 2]}
ascii
- $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. (See to OBJECT-ORIENTED INTERFACE in JSON::XS).
In Perl 5.005, there is no character having high value (more than 255). See to UNICODE HANDLING ON PERLS.
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.
- JSON::PP->new->ascii(1)->encode([chr 0x10401])
- => ["\ud801\udc01"]
latin1
- $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::XS->new->latin1->encode (["\x{89}\x{abc}"]
- => ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
See to UNICODE HANDLING ON PERLS.
utf8
- $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 Perl 5.005, any character outside the range 0..255 does not exist. See to UNICODE HANDLING ON PERLS.)
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;
- $jsontext = encode "UTF-16BE", JSON::PP->new->encode ($object);
Example, decode UTF-32LE-encoded JSON:
- use Encode;
- $object = JSON::PP->new->decode (decode "UTF-32LE", $jsontext);
pretty
- $json = $json->pretty([$enable])
This enables (or disables) all of the indent
, space_before
and
space_after
flags in one call to generate the most readable
(or most compact) form possible.
Equivalent to:
- $json->indent->space_before->space_after
indent
- $json = $json->indent([$enable])
- $enabled = $json->get_indent
The default indent space length is three.
You can use indent_length
to change the length.
space_before
- $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"}
space_after
- $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"}
relaxed
- $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...
- ]
canonical
- $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.
If you want your own sorting routine, you can give a code referece
or a subroutine name to sort_by
. See to JSON::PP OWN METHODS
.
allow_nonref
- $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::PP->new->allow_nonref->encode ("Hello, World!")
- => "Hello, World!"
allow_unknown
- $json = $json->allow_unknown ([$enable])
- $enabled = $json->get_allow_unknown
If $enable is true (or missing), then "encode" will *not* throw an exception when it encounters values it cannot represent in JSON (for example, filehandles) but instead will encode a JSON "null" value. Note that blessed objects are not included here and are handled separately by c<allow_nonref>.
If $enable is false (the default), then "encode" will throw an exception when it encounters anything it cannot encode as JSON.
This option does not affect "decode" in any way, and it is recommended to leave it off unless you know your communications partner.
allow_blessed
- $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.
convert_blessed
- $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.
filter_json_object
- $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:
filter_json_single_key_object
- $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::PP
- ->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} }
- }
shrink
- $json = $json->shrink([$enable])
- $enabled = $json->get_shrink
In JSON::XS, this flag resizes strings generated by either
encode
or decode
to their minimum size possible.
It will also try to downgrade any strings to octet-form if possible.
In 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
max_depth
- $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 a higher nesting level is detected in JSON text or a Perl
data structure, 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.
If no argument is given, the highest possible setting will be used, which is rarely useful.
See SSECURITY CONSIDERATIONS in JSON::XS for more info on why this is useful.
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.
max_size
- $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
, meaning no limit. When
decode
is called on a string that is longer then this many bytes, it will not
attempt to decode the string but throw an exception. This setting has no
effect on encode
(yet).
If no argument is given, the limit check will be deactivated (same as when
is specified).
See SSECURITY CONSIDERATIONS in JSON::XS for more info on why this is useful.
encode
- $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.
References to the integers
and
1
are converted into true
and false
.
decode
- $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
(JSON::true
), false
becomes
(
JSON::false
) and
null
becomes undef
.
decode_prefix
- ($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)
INCREMENTAL PARSING
Most of this section are copied and modified from INCREMENTAL PARSING in JSON::XS.
In some cases, there is the need for incremental parsing of JSON texts.
This module does allow you to parse a JSON stream incrementally.
It does so by accumulating text until it has a full JSON object, which
it then can decode. This process is similar to using decode_prefix
to see if a full JSON object is available, but is much more efficient
(and can be implemented with a minimum of method calls).
This module will only attempt to parse the JSON text once it is sure it
has enough text to get a decisive result, using a very simple but
truly incremental parser. This means that it sometimes won't stop as
early as the full parser, for example, it doesn't detect parenthese
mismatches. The only thing it guarantees is that it starts decoding as
soon as a syntactically valid JSON text has been seen. This means you need
to set resource limits (e.g. max_size
) to ensure the parser will stop
parsing in the presence if syntax errors.
The following methods implement this incremental parser.
incr_parse
- $json->incr_parse( [$string] ) # void context
- $obj_or_undef = $json->incr_parse( [$string] ) # scalar context
- @obj_or_empty = $json->incr_parse( [$string] ) # list context
This is the central parsing function. It can both append new text and extract objects from the stream accumulated so far (both of these functions are optional).
If $string
is given, then this string is appended to the already
existing JSON fragment stored in the $json
object.
After that, if the function is called in void context, it will simply return without doing anything further. This can be used to add more text in as many chunks as you want.
If the method is called in scalar context, then it will try to extract
exactly one JSON object. If that is successful, it will return this
object, otherwise it will return undef
. If there is a parse error,
this method will croak just as decode
would do (one can then use
incr_skip
to skip the errornous part). This is the most common way of
using the method.
And finally, in list context, it will try to extract as many objects from the stream as it can find and return them, or the empty list otherwise. For this to work, there must be no separators between the JSON objects or arrays, instead they must be concatenated back-to-back. If an error occurs, an exception will be raised as in the scalar context case. Note that in this case, any previously-parsed JSON texts will be lost.
Example: Parse some JSON arrays/objects in a given string and return them.
- my @objs = JSON->new->incr_parse ("[5][7][1,2]");
incr_text
- $lvalue_string = $json->incr_text
This method returns the currently stored JSON fragment as an lvalue, that
is, you can manipulate it. This only works when a preceding call to
incr_parse
in scalar context successfully returned an object. Under
all other circumstances you must not call this function (I mean it.
although in simple tests it might actually work, it will fail under
real world conditions). As a special exception, you can also call this
method before having parsed anything.
This function is useful in two cases: a) finding the trailing text after a JSON object or b) parsing multiple JSON objects separated by non-JSON text (such as commas).
- $json->incr_text =~ s/\s*,\s*//;
In Perl 5.005, lvalue
attribute is not available.
You must write codes like the below:
- $string = $json->incr_text;
- $string =~ s/\s*,\s*//;
- $json->incr_text( $string );
incr_skip
- $json->incr_skip
This will reset the state of the incremental parser and will remove the
parsed text from the input buffer. This is useful after incr_parse
died, in which case the input buffer and incremental parser state is left
unchanged, to skip the text parsed so far and to reset the parse state.
incr_reset
- $json->incr_reset
This completely resets the incremental parser, that is, after this call, it will be as if the parser had never parsed anything.
This is useful if you want ot repeatedly parse JSON objects and want to ignore any trailing data, which means you have to reset the parser after each successful decode.
See to INCREMENTAL PARSING in JSON::XS for examples.
JSON::PP OWN METHODS
allow_singlequote
- $json = $json->allow_singlequote([$enable])
If $enable
is true (or missing), then decode
will accept
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.
allow_barekey
- $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"}');
allow_bignum
- $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 in JSON::XS aboout the normal conversion of JSON number.
loose
- $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 SSECURITY CONSIDERATIONS in JSON::XS.
escape_slash
- $json = $json->escape_slash([$enable])
According to JSON Grammar, slash (U+002F) is escaped. But default JSON::PP (as same as JSON::XS) encodes strings without escaping slash.
If $enable
is true (or missing), then encode
will escape slashes.
indent_length
- $json = $json->indent_length($length)
JSON::XS indent space length is 3 and cannot be changed. JSON::PP set the indent space length with the given $length. The default is 3. The acceptable range is 0 to 15.
sort_by
- $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 in encoding JSON objects.
- $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
'JSON::PP::'.
If $integer is set, then the effect is same as canonical
on.
INTERNAL
For developers.
- PP_encode_box
Returns
- {
- depth => $depth,
- indent_count => $indent_count,
- }
- PP_decode_box
Returns
- {
- text => $text,
- at => $at,
- ch => $ch,
- len => $len,
- depth => $depth,
- encoding => $encoding,
- is_valid_utf8 => $is_valid_utf8,
- };
MAPPING
This section is copied from JSON::XS and modified to JSON::PP
.
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 (in which case you lose roundtripping ability, as the JSON number will be re-encoded toa JSON string).Numbers containing a fractional or exponential part will always be represented as numeric (floating point) values, possibly at a loss of precision (in which case you might lose perfect roundtripping ability, but the JSON number will still be re-encoded as a JSON number).
Note that precision is not accuracy - binary floating point values cannot represent most decimal fractions exactly, and when converting from and to floating point,
JSON
only guarantees precision up to but not including the leats significant bit.When
allow_bignum
is enable, the big integers and the numeric can be optionally converted into Math::BigInt and Math::BigFloat objects. - true, false
These JSON atoms become
JSON::PP::true
andJSON::PP::false
, respectively. They are overloaded to act almost exactly like the numbers1
and. You can check wether a scalar is a JSON boolean by using the
JSON::is_bool
function.- print JSON::PP::true . "\n";
- => true
- print JSON::PP::true + 1;
- => 1
- 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::PP::null
returnsunddef
.
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. - 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
and
1
, which get turned intofalse
andtrue
atoms in JSON. You can also useJSON::false
andJSON::true
to improve readability.- to_json [\0,JSON::PP::true] # yields [false,true]
- JSON::PP::true, JSON::PP::false, JSON::PP::null
These special values become JSON true and JSON false values, respectively. You can also use
\1
and\0
directly if you want.JSON::PP::null returns
undef
. - blessed objects
Blessed objects are not directly representable in JSON. See the
allow_blessed
andconvert_blessed
methods on various options on how to deal with this: basically, you can choose between throwing an exception, encoding the reference as if it weren't blessed, or provide your own serialiser method.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
values, scalars that have last been used in a string context before encoding as JSON strings, and anything else as number value:You can force the type to be a string by stringifying it:
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 force the type in other, less obscure, ways.
Note that numerical precision has the same meaning as under Perl (so binary to decimal conversion follows the same rules as in Perl, which can differ to other languages). Also, your perl interpreter might expose extensions to the floating point numbers of your platform, such as infinities or NaN's - these cannot be represented in JSON, and it is an error to pass those in.
- Big Number
When
allow_bignum
is enable,encode
convertsMath::BigInt
objects andMath::BigFloat
objects into JSON numbers.
UNICODE HANDLING ON PERLS
If you do not know about Unicode on Perl well, please check A FEW NOTES ON UNICODE AND PERL in JSON::XS.
Perl 5.8 and later
Perl can handle Unicode and the JSON::PP de/encode methods also work properly.
Reuturns "\u3042"
and "\ud808\udf45"
respectively.
- $json->allow_nonref->decode('"\u3042"');
- $json->allow_nonref->decode('"\ud808\udf45"');
Returns UTF-8 encoded strings with UTF8 flag, regarded as U+3042
and U+12345
.
Note that the versions from Perl 5.8.0 to 5.8.2, Perl built-in join
was broken,
so JSON::PP wraps the join
with a subroutine. Thus JSON::PP works slow in the versions.
Perl 5.6
Perl can handle Unicode and the JSON::PP de/encode methods also work.
Perl 5.005
Perl 5.005 is a byte sementics world -- all strings are sequences of bytes. That means the unicode handling is not available.
In encoding,
Returns B
and E
, as chr
takes a value more than 255, it treats
as $value % 256
, so the above codes are equivalent to :
In decoding,
- $json->decode('"\u00e3\u0081\u0082"');
The returned is a byte sequence 0xE3 0x81 0x82
for UTF-8 encoded
japanese character (HIRAGANA LETTER A
).
And if it is represented in Unicode code point, U+3042
.
Next,
- $json->decode('"\u3042"');
We ordinary expect the returned value is a Unicode character U+3042
.
But here is 5.005 world. This is 0xE3 0x81 0x82
.
- $json->decode('"\ud808\udf45"');
This is not a character U+12345
but bytes - 0xf0 0x92 0x8d 0x85
.
TODO
SEE ALSO
Most of the document are copied and modified from JSON::XS doc.
RFC4627 (http://www.ietf.org/rfc/rfc4627.txt)
AUTHOR
Makamaka Hannyaharamitu, <makamaka[at]cpan.org>
COPYRIGHT AND LICENSE
Copyright 2007-2014 by Makamaka Hannyaharamitu
This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
- NAME
- SYNOPSIS
- VERSION
- NOTE
- DESCRIPTION
- FUNCTIONAL INTERFACE
- HOW DO I DECODE A DATA FROM OUTER AND ENCODE TO OUTER
- METHODS
- new
- ascii
- latin1
- utf8
- pretty
- indent
- space_before
- space_after
- relaxed
- canonical
- allow_nonref
- allow_unknown
- allow_blessed
- convert_blessed
- filter_json_object
- filter_json_single_key_object
- shrink
- max_depth
- max_size
- encode
- decode
- decode_prefix
- INCREMENTAL PARSING
- JSON::PP OWN METHODS
- INTERNAL
- MAPPING
- UNICODE HANDLING ON PERLS
- TODO
- SEE ALSO
- AUTHOR
- COPYRIGHT AND LICENSE