Rohan Almeida’s Blog
Perl Developer. Linux Advocacy. Practicing Guitarist.

The other day I had the need of converting a hash structure to XML format. The XML::Simple CPAN module is the best tool for this. However there are some options you need to be aware of to get your XML the way you want. The default options for the XMLout function may leave you confused and bothered.

Lets say you have a simple hash structure like this:

$href = {
'CD' => {
'Audio' => {
'Title' => 'Money For Nothing',
'Artist' => 'Dire Straits',
},
},
};


Now go ahead and use the XMLout function like this:

use XML::Simple;
my $xml = XMLout($href);
print "$xml\n";

Here is what you get:

<opt>
  <CD name="Audio" Artist="Dire Straits" Title="Money For Nothing" />
</opt>

Yeah! You need to go through the docs to find the right options. Firstly, what can be seen is that all the elements are lined up as attributes of the root “CD” element. Assuming, you don’t want this (I didn’t), you can make use of the NoAttr option. Like this:

$xml = XMLout(
        $href,
        NoAttr => 1,
);
print "$xml\n";

And this is what we get:

<opt>
  <CD>
    <name>Audio</name>
    <Artist>Dire Straits</Artist>
    <Title>Money For Nothing</Title>
  </CD>
</opt>

Much Better!

However, we still have that that irritating “<name>Audio</name>” string coming up. It turns out that XML::Simple uses a default value for the KeyAttr option of which name is one of them. Hence you see that “<name>Audio</name>” thing. You can turn this off, by setting the KeyAttr value to an empty list. At the same time lets get rid of the root element which by default is opt. Do this by setting the RootName option to an undef value.

Ok. Now lets check it out.

$xml = XMLout(
        $href,
        NoAttr => 1,
        KeyAttr => [],
        RootName => undef,
);
print "$xml\n";

Here is the output:

<CD>
    <Audio>
      <Artist>Dire Straits</Artist>
      <Title>Money For Nothing</Title>
    </Audio>
</CD>

Much, Much Better! Of course, assuming this is the way you intended your XML to look like.

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This entry was posted on Sunday, October 23rd, 2005 at 11:48 am and is filed under Perl. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.