Not able to get value of element in XPath context in perl

Question

I am not able to get value for chapter_title, though it gets values for other attributes. I have shown the structure of the xml.

use XML::LibXML;

my %chapter_columns = 
(
'Book_Id' => 'substring-before(@id,"ch")',
'Chapter_Doi' => 'book:meta/@doi',
'Chapter_Id' => '@id',
'Chapter_Title' => 'book:locator[contains(@xlink:href, "format=epub")]/@xlink:title',
'Chapter_Doi_Prefix' => 'substring-before(book:meta/@doi,"/")',
);

my $parser = XML::LibXML->new();
my $dom = $parser->parse_file("book.xml");
my $root = $dom->documentElement();
my $xpc = XML::LibXML::XPathContext->new($root);

$xpc->registerNs('book', 'http://api.abc.org/Book/1.0/');
$xpc->registerNs('xlink', 'http://www.w3.org/1999/xlink');

foreach my $chapter_node ($xpc->findnodes('/book:bookResource/book:book/
book:contents/book:chapter'))
{
foreach my $col(qw/Chapter_Id Chapter_Title Book_Id Chapter_Doi Chapter_Doi_Prefix
Chapter_Id/)
{
print $chapter_node->findvalue($chapter_columns{$col}), "
";
}
}

The structure of the 'book.xml' file is as below:

I wonder what causes it fail to get the value. Any help would be appreciable. Sorry, some part of xml was missing.

And the exact error I get is

XPath error : Undefined namespace prefix error : xmlXPathCompOpEval: parameter error error : xmlXPathCompiledEval: 1 objects left on the stack.

ikegami · Accepted Answer

You didn't use the XPC, so it doesn't know waht xlink means in your path.

print $chapter_node->findvalue($chapter_columns{$col}), "
";

should be

print $xpc->findvalue($chapter_columns{$col}, $chapter_node), "
";

Not able to get value of element in XPath context in perl

Answers (1)

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