How to convert a JSON file to Delimited File using perl. - json

Question

#/usr/lib/perl
use lib qw(..);
use JSON qw( );
open json_fh, "<$ARGV[0]" or die "Couldn't open file $ARGV[0]!\n";
open csv_fh, ">$ARGV[1]" or die "Couldn't open file $ARGV[1]!\n";
#json_text =<json_fh>;
close json_fh;
foreach $json_text( #json_text )
{
chomp $json_text;
$json = JSON->new;
$data = $json->decode($json_text);
$id=$data->{_id};
#lines=#{$data->{accounts}};
foreach $line ( #lines )
{
$accountNumber = $line->{accountNumber};
$accountType = $line->{accountType};
$cardType = $line->{cardType};
$cardSubType = $line->{cardSubType};
$protectionMethod = $line->{protectionMethod};
$protectionSource = $line->{protectionSource};
$expirationDate = $line->{expirationDate};
$nameOnAccount = $line->{nameOnAccount};
$cardStatus = $line->{cardStatus};
$cardHolderType = $line->{cardHolderType};
$createdBy = $line->{createdBy};
$addressId = $line->{addressId};
$productType = $line->{productType};
$isDefaultAccount = $line->{isDefaultAccount};
#Write to the file in delimited file format
print csv_fh "$id|$accountNumber|$accountType|$cardType|$cardSubType|$protectionMethod|$protectionSource|$expirationDate|$nameOnAccount|$cardStatus|$cardHolderType|$createdBy|$addressId|$productType|$isDefaultAccount\n";
}
}
close csv_fh;
This is a perl script that, I created to convert the JSON file to a delimited file, If the element names are known.
Could anyone please help me to modify the code so that this conversion can be done, when the element names are unknown.

Answer 1

Assuming that every account has the same fields —it makes no sense otherwise— you can use the following:
my $json_parser = JSON->new;
my #headers;
for my $json_doc (#json_docs) {
my $data = $json_parser->decode($json_doc);
my $id = $data->{_id};
for my $account (#{ $data->{accounts} }) {
if (!#headers) {
#headers = sort keys %$account;
say join "|", 'id', #headers;
}
say join "|", $id, #$account{#headers};
}
}

Answer 2

You didn't provide an example input file, so I'm guessing it is something like this:
{ "accounts": [ { "_id": "1", "accountNumber": "99999", "accountType": "acctTypeA", "cardType": "cardTypeA", "cardSubType": "cardSubTypeA", "protectionMethod": "protectionMethodA", "protectionSource": "protectionSourceA", "expirationDate": "2020-09", "nameOnAccount": "First Last", "cardStatus": "OK", "cardHolderType": "CHTypeA", "createdBy": "userX", "addressId": "444", "productType": "prodTypeA", "isDefaultAccount": "1", "optional": "OptA" } ] }
You're pretty close, but usually the entire file is a JSON record, so you don't loop line-by-line, you create a data structure (hashref) that represents the entire file (i.e. you only need to do $json->decode once per file).
Additionally, I'd suggest some checks to validate input, such as missing fields; you can see I have it die with an error message if any field is missing.
#!/usr/bin/env perl
use strict;
use lib qw(..);
use JSON qw( );
#ARGV == 2 or die("Infile, Outfile required\n");
open json_fh, "<$ARGV[0]" or die "Couldn't open file $ARGV[0]!\n";
open csv_fh, ">$ARGV[1]" or die "Couldn't open file $ARGV[1]!\n";
my $json_text =<json_fh>;
close json_fh;
my $json = JSON->new->allow_nonref;
my $data = $json->decode($json_text);
my $accounts = $data->{accounts};
my #required = qw(_id accountNumber accountType cardType cardSubType protectionMethod protectionSource expirationDate nameOnAccount cardStatus cardHolderType createdBy addressId productType isDefaultAccount);
my #opt = (); # learn these
my %col; # key => column index
my $lastIndex;
for (my $i=0; $i<=$#required; ++$i) { $lastIndex = $col{$required[$i]} = $i }
print "There are ", $lastIndex+1, " required cols\n";
foreach my $rec ( #$accounts )
{
my #row;
foreach my $key ( keys %$rec )
{
if ( ! exists($col{$key}) ) {
# new (optional) key
push #opt, $key;
$col{$key} = ++$lastIndex;
print "New col: $key (col ", $lastIndex+1, ")\n";
}
$row[$col{$key}] = $rec->{$key};
}
# check for all required
for (my $i=0; $i<=$#required; ++$i) {
defined($row[$i]) or die("Missing: $required[$i]\n");
}
#Write to the file in delimited file format
print csv_fh join("|", #row), "\n";
}
close csv_fh;