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JSON::PP.3pm

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;
  $pretty_printed_unencoded = $coder->encode ($perl_scalar);
  $perl_scalar = $coder->decode ($unicode_json_text);
 
  # 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;
 
 

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 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). But when some options are set, loose chcking features are available.

FUNCTIONS

$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)
 
 

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".

METHODS

new

Rturns a new JSON::PP object that can be used to de/encode JSON strings.

$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

$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''.

$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;
   $jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
 
 

Example, decode UTF-32LE-encoded JSON:

   use Encode;
   $object = JSON::XS->new->decode (decode "UTF-32LE", $jsontext);
 
 

$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
 
 

Example, pretty-print some simple structure:

    my $json = JSON->new->pretty(1)->encode ({a => [1,2]})
    =>
    {
       "a" : [
          1,
          2
       ]
    }
 
 

The indent space length is three.

$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 default indent space lenght is three. You can use "indent_length" to change the 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.

See to ``OBJECT-ORIENTED INTERFACE'' in JSON::XS

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".

$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!"
 
 

See to ``OBJECT-ORIENTED INTERFACE'' in JSON::XS.

$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.

See to ``OBJECT-ORIENTED INTERFACE'' in JSON::XS

$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.

See to ``OBJECT-ORIENTED INTERFACE'' in JSON::XS

$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}');
 
 

See to ``OBJECT-ORIENTED INTERFACE'' in JSON::XS

$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} }
    }
 
 

See to ``OBJECT-ORIENTED INTERFACE'' in JSON::XS

$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

$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.

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.

$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 ``SSECURITY CONSIDERATIONS'' in JSON::XS for more info on why this is useful.

$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.

See to ``OBJECT-ORIENTED INTERFACE'' in JSON::XS

$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".

See to ``OBJECT-ORIENTED INTERFACE'' in JSON::XS

($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

JSON::PP OWN METHODS

$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.

$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'' in JSON::XS aboout the normal 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 ``SSECURITY CONSIDERATIONS'' in JSON::XS.

$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.

$json = $json->as_nonblessed

(EXPERIMENTAL) 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.

$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.

$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,
             is_utf8 => $is_utf8,
             depth   => $depth,
             encoding      => $encoding,
             is_valid_utf8 => $is_valid_utf8,
         };
 
 

MAPPING

See to ``MAPPING'' in JSON::XS.

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.

     $json->allow_nonref->encode(chr hex 3042);
     $json->allow_nonref->encode(chr hex 12345);
 
 

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,

     $json->allow_nonref->encode(chr hex 3042);  # hex 3042 is 12354.
     $json->allow_nonref->encode(chr hex 12345); # hex 12345 is 74565.
 
 

Returns "B" and "E", as "chr" takes a value more than 255, it treats as "$value % 256", so the above codes are equivalent to :

     $json->allow_nonref->encode(chr 66);
     $json->allow_nonref->encode(chr 69);
 
 

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.

JSON::XS

RFC4627 (<http://www.ietf.org/rfc/rfc4627.txt>)

AUTHOR

Makamaka Hannyaharamitu, <makamaka[at]cpan.org>

COPYRIGHT AND LICENSE

Copyright 2008 by Makamaka Hannyaharamitu

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.