halfbaked has asked for the wisdom of the Perl Monks concerning the following question:

I need a really simple way to parse a tiny XML document, but I'm having trouble finding the proper solution.

I'm using XML::LibXML and I can easily pull out the doctype, charset and other data I need, but I can't figure out how to grab a list of the errors located in the errorlist tag.

Here's an example of the XML I need to parse, I can't change this. 
<?xml version="1.0" encoding="UTF-8"?>
<env:Envelope xmlns:env="http://www.w3.org/2003/05/soap-envelope">
<env:Body>
<m:markupvalidationresponse env:encodingStyle="http://www.w3.org/2003/
+05/soap-encoding" xmlns:m="http://www.w3.org/2005/10/markup-validator
+">
    <m:uri>http://www.perlmonks.org/</m:uri>
    <m:checkedby>http://localhost/w3c-markup-validator/</m:checkedby>
    <m:doctype>-//W3C//DTD HTML 4.0 Transitional//EN</m:doctype>
    <m:charset>utf-8</m:charset>
    <m:validity>false</m:validity>
    <m:errors>
        <m:errorcount>59</m:errorcount>
        <m:errorlist>
            <m:error>
                <m:line>11</m:line>
                <m:col>66</m:col>                                     
+      
                <m:message>document type does not allow element &quot;
+LINK&quot; here</m:message>
            </m:error>
           
            <m:error>
                <m:line>14</m:line>
                <m:col>41</m:col>                                     
+      
                <m:message>document type does not allow element &quot;
+LINK&quot; here</m:message>
            </m:error>
           
            <m:error>
                <m:line>21</m:line>
                <m:col>4</m:col>                                      
+     
                <m:message>document type does not allow element &quot;
+META&quot; here</m:message>
            </m:error>
        </m:errorlist>
    </m:errors>
    <m:warnings>
        <m:warningcount>0</m:warningcount>
        <m:warninglist>
     <m:warning><m:message>No Character Encoding Found!
    
      Falling back to 
    
    UTF-8.
  </m:message></m:warning>
        </m:warninglist>
    </m:warnings>
</m:markupvalidationresponse>
</env:Body>
</env:Envelope>

[download]


Here's a snippet of the code I'm using to read the XML. 
    my $ua = LWP::UserAgent->new();
    my $response = $ua->request($request);
    my $parser = XML::LibXML->new();
    my $doc = $parser->parse_string($response->content);

    Kube::Demonize::logmsg($response->content);
    #for (my $i = 0; $i < @errorlist; $i++) {
    #    Kube::Demonize::logmsg(sprintf("%s\n", $errorlist[$i]->getEle
+mentsByTagName('m:line')->textContent));
    #}
    
    foreach my $d ($doc->getElementsByTagName('m:doctype')) {
        print $d->textContent;
    }
    
    foreach my $d ($doc->getElementsByTagName('m:validity')) {
        print $d->textContent;
    }
    
    foreach my $d ($doc->getElementsByTagName('m:charset')) {
        print $d->textContent;
    }

[download]


Don't get bogged down in the implementation, this is just a prototype to illustrate what I'm trying to do.

I'm just looking for the easiest way to pull out the errors, stuff them in a Perl data structure, like an array of hashes.

Something like this: 
@errors[0] = %error(
       line=>120,
       col=>2,
       message=>'Tag not allowed');
@errors[1] = %error(
       line=>220,
       col=>3,
       message=>'Another error?');

[download]


Thanks.

Replies are listed 'Best First'.
Re: Easiest way to parse a simple XML file?
by Tanktalus (Canon) on Dec 11, 2008 at 00:31 UTC

    My swiss-army-knife for XML is XML::Twig, which I used for this: 

    #!/usr/bin/perl
use strict;
use warnings;

use XML::Twig;

my $t = XML::Twig->new();
$t->parsefile('x.xml');

my @errors = map {
    my %d = map {
        (my $tag = $_->tag()) =~ s/^m://;
        $tag => $_->text()
    } $_->children();
    \%d
} $t->get_xpath('//m:error');

use Data::Dumper; print Dumper \@errors;

    [download]
    The output is: 
    $VAR1 = [
          {
            'col' => '66',
            'message' => 'document type does not allow element "LINK" 
+here',
            'line' => '11'
          },
          {
            'col' => '41',
            'message' => 'document type does not allow element "LINK" 
+here',
            'line' => '14'
          },
          {
            'col' => '4',
            'message' => 'document type does not allow element "META" 
+here',
            'line' => '21'
          }
        ];

    [download]
    You can do the same for warnings and whatever else you have. With some practice with the xpath, you can ensure that you're getting just what you want.

[reply]
[d/l]
[select]
      Thanks Tanktalus, I went with XML::Twig as you suggested, it seems the easiest way to go, but I always kind of scratch my head whenever I have to parse XML, it never seems as simple as it should be.

      Maybe it's just me.

      Thanks again.
[reply]
Re: Easiest way to parse a simple XML file?
by ig (Vicar) on Dec 11, 2008 at 00:49 UTC

    And XML::Simple works

    use strict;
use warnings;
use Data::Dumper;

use XML::Simple;

my $ref = XMLin('test.xml');

print Dumper($ref->{"env:Body"}->{"m:markupvalidationresponse"}->{"m:e
+rrors"}->{"m:errorlist"}->{"m:error"});

    [download]

    produces

    $VAR1 = [
          {
            'm:line' => '11',
            'm:col' => '66',
            'm:message' => 'document type does not allow element "LINK
+" here'
          },
          {
            'm:line' => '14',
            'm:col' => '41',
            'm:message' => 'document type does not allow element "LINK
+" here'
          },
          {
            'm:line' => '21',
            'm:col' => '4',
            'm:message' => 'document type does not allow element "META
+" here'
          }
        ];

    [download]
[reply]
[d/l]
[select]
Re: Easiest way to parse a simple XML file?
by Anonymous Monk on Dec 11, 2008 at 10:08 UTC
[reply]
Re: Easiest way to parse a simple XML file?
by Jenda (Abbot) on Dec 12, 2008 at 17:30 UTC 
    use strict;
use XML::Rules;

my $parser = XML::Rules->new(
    stripspaces => 7,
    namespaces => {
        'http://www.w3.org/2005/10/markup-validator' => '',
        'http://www.w3.org/2003/05/soap-envelope' => 'env',
    },
    start_rules => {
        warnings => 'skip',
    },
    rules => {
        _default => 'content',
        error => 'as array no content',
        errorlist => 'no content',
        errors => sub { return errors => $_[1]->{errorlist}{error}},
        warning => sub {return warning => $_[1]->{message}},
        'markupvalidationresponse' => 'no content',
        'env:Body' => 'as is',
        'env:Envelope' => sub {return $_[1]->{'env:Body'}{markupvalida
+tionresponse}},
    }
);

my $data = $parser->parse(\*DATA);
use Data::Dumper;

print Dumper($data);

__DATA__
<?xml version="1.0" encoding="UTF-8"?>
<env:Envelope xmlns:env="http://www.w3.org/2003/05/soap-envelope">
...

    [download]

    XML::Rules lets you tweak and trim the structure produced by parsing the XML so that you end up with only the stuff you need in a format that's most convenient to you.

    Jenda
    Support Denmark!
    Defend the free world!

[reply]
[d/l]

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