Parsing JSON data in Perl - json

Question

I am parsing JSON data which is in .json file. Here I have 2 formats of JSON data files.
I could parse first JSON file - file is shown below:
file1.json
{
"sequence" : [ {
"type" : "type_value",
"attribute" : {
"att1" : "att1_val",
"att2" : "att2_val",
"att3" : "att3_val",
"att_id" : "1"
}
} ],
"current" : 0,
"next" : 1
}
Here is my script:
#/usr/lib/perl
use strict;
use warnings;
use Data::Dumper;
use JSON;
my $filename = $ARGV[0]; #Pass json file as an argument
print "FILE:$filename\n";
my $json_text = do {
open(my $json_fh, "<:encoding(UTF-8)", $filename)
or die("Can't open \$filename\": $!\n");
local $/;
<$json_fh>
};
my $json = JSON->new;
my $data = $json->decode($json_text);
my $aref = $data->{sequence};
my %Hash;
for my $element (#$aref) {
my $a = $element->{attribute};
next if(!$a);
my $aNo = $a->{att_id};
$Hash{$aNo}{'att1'} = $a->{att1};
$Hash{$aNo}{'att2'} = $a->{att2};
$Hash{$aNo}{'att3'} = $a->{att3};
}
print Dumper \%Hash;
Everything is getting stored in %Hash and when I print Dumper of the %Hash I am getting following result.
$VAR1 = {
'1' => {
'att1' => 'att1_val',
'att2' => 'att2_val',
'att3' => 'att3_val'
}
};
But when I parse second set of JSON file, I am getting empty hash by using the above script.
Output:
$VAR1 = {};
Here is the JSON file -
file2.json
{
"sequence" : [ {
"type" : "loop",
"quantity" : 8,
"currentIteration" : 0,
"sequence" : [ {
"type" : "type_value",
"attribute" : {
"att1" : "att1_val",
"att2" : "att2_val",
"att3" : "att3_val",
"att_id" : "1"
}
} ]
} ]
}
We can see two sequence in above JSON data file, which is causing the problem.
Can somebody tell me what I am missing in the script inorder to parse file2.json.

Answer 1

One possibility might be to check the type field to differentiate between the two file formats:
# [...]
for my $element (#$aref) {
if ( $element->{type} eq "loop" ) {
my $aref2 = $element->{sequence};
for my $element2 ( #$aref2 ) {
get_attrs( $element2, \%Hash );
}
}
else {
get_attrs( $element, \%Hash );
}
}
sub get_attrs {
my ( $element, $hash ) = #_;
my $a = $element->{attribute};
return if(!$a);
my $aNo = $a->{att_id};
$hash->{$aNo}{'att1'} = $a->{att1};
$hash->{$aNo}{'att2'} = $a->{att2};
$hash->{$aNo}{'att3'} = $a->{att3};
}

Answer 2

Please see the following code if it fits your requirements
#!/usr/bin/env perl
#
# vim: ai:sw=4:ts=4
#
use strict;
use warnings;
use feature 'say';
use Data::Dumper;
use JSON;
my $debug = 0; # debug flag
my $filename = shift; # Pass json file as an argument
say "FILE: $filename";
open(my $json_fh, "<:encoding(UTF-8)", $filename)
or die("Can't open \$filename\": $!\n");
my $json_data = do { local $/; <$json_fh> };
close $json_fh;
my $json = JSON->new;
my $data = $json->decode($json_data);
say Dumper($data) if $debug;
my $data_ref;
my %Hash;
$data_ref = $data->{sequence}[0]{attribute}
if $filename eq 'file1.json';
$data_ref = $data->{sequence}[0]{sequence}[0]{attribute}
if $filename eq 'file2.json';
say Dumper($data_ref) if $debug;
my #fields = qw/att1 att2 att3/;
my $aNo = $data_ref->{att_id};
my %data_hash;
#data_hash{#fields} = $data_ref->{#fields};
$Hash{$aNo} = \%data_hash;
say Dumper(\%Hash);