I have to parse XML formatted messages being sent across a network connection and prefer to use XPath. I thought I was being clever by using code like the below to avoid a fatal error in the network server while parsing the messages:

use XML::XPath;
my ($xml, $xp);
$xml = “not xml”;
eval {
  $xp = XML::XPath->new(xml => $xml);
};
if ($@) {
 print “Parsing failed\n”;
}
…..
[download]

The problem is that apparently XML::XPath doesn’t check for valid XML on object creation. It returns the object fine, which is far from ideal for my needs. I don’t think anyone will ever send me invalid XML since I wrote the client apps too, but I don’t want to bet a midnight call in on it either. The solution involves also using XML::Parser and letting it do the parsing. If everything is okay, then we create an XPath object.

use XML::XPath;
use XML::Parser;
my ($xml, $xp);
$xml = “not xml”;
eval {
 my $po = new XML::Parser;
 $po->parse($xml);
};
if ($@) {
 print “Parsing failed\n”;    #handle error
} else {
 $xp = XML::XPath->new(xml => $xml);
}
…..
[download]

The XML::XPath documentation says that the constructor will take a parser argument that is an XML::Parser object but this seems to work just fine too (although probably has higher overhead). What would be ideal is if XML::XPath just did XML validation before returning the object.