in reply to XML::XPath and preserving CDATA fields

Getting <br> instead of <br> is certainly a bug, but note that using the latest version (1.12) I get the right output though, so if you are using an earlier version you might want to upgrade.

As for XML::XPath turning the CDATA section into regular PCDATA with entities for & and <, I would think this is a design choice, the fact that there ever was a CDATA section seems to be totally ignored by XML::XPath. For XML purposes the 2 versions are equivalent, CDATA sections are just a shortcut to avoid typing a bunch of entities. That said I know for a lot of applications there is a difference between the 2, especially when you want to include regular HTML within an XML document, and I don't really like modules that don't preserve the original form of the input document, but hey,XML::XPath is so convenient, it might be worth using it and writing an extra step that restores the CDATA section, so here is my solution:

#!/usr/bin/perl -w
use strict;

use XML::XPath;

undef $/;

my $XML=<DATA>;

my $xpath = XML::XPath->new('xml' => $XML);
foreach my $node ($xpath->findnodes('/foo/bar/text')->get_nodelist) { 
    my $data = your_munge_function($node->string_value);
    my $id = $node->getAttribute('id');
    $xpath->setNodeText('/foo/bar/text[@id="' . $id . '"]', $data);
}


my $newXML = $xpath->findnodes_as_string('/');

# safe because XML::XPath entiti-zes > in attributes
$newXML=~ s{(<text[^>]*>)(.*?)(</text>)}
           {$1 . cdata_ize($2) . $3}eg;

print $newXML;

sub your_munge_function
  { return "munged $_[0]"; }

sub cdata_ize
  { my $text= shift;
    $text=~ s{&amp;}{&}g;
    $text=~ s{&lt;}{<}g;
    return "<![CDATA[$text]]>";
  }

__DATA__
<foo>
<bar>
<text id="text1>"><![CDATA[La dee da de da.<br>Foo bar baz]]></text>
</bar>
</foo>

[download]

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Re: Re: XML::XPath and preserving CDATA fields
by Anonymous Monk on May 30, 2002 at 15:11 UTC
    Hi mirod,

    Thanks a lot for your suggestion. I think I am going to end up doing something similar to that. I was hoping there would be a more elegant solution than manually fixing the CDATA fields, though. :)

[reply]

      OK, I know everybody was waiting for me to use my hammer ;--) ... here is a solution using XML::Twig. One big caveat though is that XML::Twig's version of XPath is way, way, _WAY_ less powerful than what XML::XPath offers. No functions except string, complex sub expressions not supported, you name it. It does /foo/bar/text/* though ;--)

      #!/usr/bin/perl -w
use strict;

use XML::Twig;

my $twig = XML::Twig->new( pretty_print => 'indented');
$twig->parse( \*DATA);

# the * means that the nodes returned will be either #PCDATA 
# or #CDATA, this would not work if the content of text was...
# not text but included sub elements
foreach my $node ($twig->find_nodes('/foo/bar/text/*')) { 
    my $data = your_munge_function($node->text);
    $node->set_text( $data);
}


$twig->print;

sub your_munge_function
  { return "munged $_[0]"; }

__DATA__
<foo>
<bar>
<text id="text1>"><![CDATA[La dee da de da.<br>Foo bar baz]]></text>
<text id="text2>">a normal text></text>
</bar>
</foo>

      [download]
[reply]
[d/l]
        Wahoo! I just tested it and that solution will work perfectly. XML::Twig supports what I need to do and the code changes will be pretty minor. Thanks for your help!

        -Mike

[reply]

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