JSON with Perl

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This tutorial will teach you how to encode and decode JSON objects using Perl programming language. Let's start with preparing environment to start our programming with Perl for JSON.

Environment

Before you start with encoding and decoding JSON using Perl, you will need to install JSON module which can be obtained from CPAN. Once you downloaded JSON-2.53.tar.gz or any other latest version, follow the following steps:

$tar xvfz JSON-2.53.tar.gz
$cd JSON-2.53
$perl Makefile.PL
$make
$make install

JSON Functions

FunctionLibraries
encode_json Converts the given Perl data structure to a UTF-8 encoded, binary string.
decode_jsonDecodes a JSON string.
to_jsonConverts the given Perl data structure to a json string.
from_jsonExpects a json string and tries to parse it, returning the resulting reference.
convert_blessedUse this function with true value so that Perl can use TO_JSON method on the object's class to convert an object into JSON.

Encoding JSON in Perl (encode_json)

Perl encode_json() function converts the given Perl data structure to a UTF-8 encoded, binary string.

Syntax:

$json_text = encode_json ($perl_scalar );

or

$json_text = JSON->new->utf8->encode($perl_scalar);

Example

The following example shows arrays under JSON with Perl:

#!/usr/bin/perl
use JSON;

my %rec_hash = ('a' => 1, 'b' => 2, 'c' => 3, 'd' => 4, 'e' => 5);
my $json = encode_json \%rec_hash;
print "$json\n";

While executing, this will produce following result:

{"e":5,"c":3,"a":1,"b":2,"d":4}

The following example shows how Perl objects can be converted into JSON:

#!/usr/bin/perl

package Emp;
sub new
{
    my $class = shift;
    my $self = {
        name => shift,
        hobbies  => shift,
        birthdate  => shift,
    };
    bless $self, $class;
    return $self;
}
sub TO_JSON { return { %{ shift() } }; }

package main;
use JSON;

my $JSON  = JSON->new->utf8;
$JSON->convert_blessed(1);

$e = new Emp( "sachin", "sports", "8/5/1974 12:20:03 pm");
$json = $JSON->encode($e);
print "$json\n";

While executing, this will produce following result:

{"birthdate":"8/5/1974 12:20:03 pm","name":"sachin","hobbies":"sports"}

Decoding JSON in Perl (decode_json)

Perl decode_json() function is used for decoding JSON in Perl. This function returns the value decoded from json to appropriate Perl type.

Syntax:

$perl_scalar = decode_json $json_text

or

$perl_scalar = JSON->new->utf8->decode($json_text)

Example

The following example shows how Perl can be used to decode JSON objects. Here you will need to install Data::Dumper module if you already do not have it on your machine.

#!/usr/bin/perl
use JSON;
use Data::Dumper;

$json = '{"a":1,"b":2,"c":3,"d":4,"e":5}';

$text = decode_json($json);
print  Dumper($text);

While executing, this will produce following result:

$VAR1 = {
          'e' => 5,
          'c' => 3,
          'a' => 1,
          'b' => 2,
          'd' => 4
        };


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