XPath with node names and attributes...

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

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Re: XPath with node names and attributes... by Corion (Patriarch) on Oct 16, 2009 at 15:58 UTC
Just give the XPath engine properly formatted XPath queries and all will work. In your case, that likely means using: `root/head/node1@att1` [download] instead of `root/head/node1/@att1` [download]	[reply] [d/l] [select]
Re^2: XPath with node names and attributes... by mirod (Canon) on Oct 16, 2009 at 16:17 UTC
There must be something I am missing here. `root/head/node1@att1` is invalid, while `root/head/node1/@att1` works just fine. I tested that with several tools, including XML::LibXML. I would actually had the starting slash: `/root/head/node1@att1`.	[reply] [d/l] [select]
Re^2: XPath with node names and attributes... by biswanath_c (Beadle) on Oct 16, 2009 at 16:05 UTC
I tried using the XPath that you suggested (root/head/node1@att1). But in that case, i call findnodes(<XPath with attribute>) and iterate thru the resulting array and call findValue(".") on the array elements, it returns nothing! i tried calling nodeValue() also, that too returned nothing! i tried textContent(), it returned value of the node but not the value of the attribute! What do i do?	[reply]
Re^3: XPath with node names and attributes... by Corion (Patriarch) on Oct 17, 2009 at 13:23 UTC
Actually, I am wrong and you are right - queries for attributes also need `/` as the separator. I thought the `@` would separate a element node from an attribute node, as the documentation seems to suggest to me in `//title[@lang]`, but upon actually trying it, I find that only `node/@attribute` works for me, and likely is the correct query to use.	[reply] [d/l] [select]
Re: XPath with node names and attributes... by thunders (Priest) on Oct 16, 2009 at 16:56 UTC
Perhaps It would help if you provide some example code and xml that demonstrates the problem you are having.	[reply]
Re^2: XPath with node names and attributes... by biswanath_c (Beadle) on Oct 16, 2009 at 17:33 UTC
okay! here we go. I am just giving an example here that I tested and which demonstrates my problem: The XML: `<root> <head> <node1 attr1="Node1 Attribute"> Node1 Value </node1> </head> </root>` [download] The PERL script that tries to read the attribute: use XML::LibXML; $inp = $ARGV[0]; # create object my $parser = XML::LibXML->new(); # read input XML file my $inp_tree = $parser->parse_file($inp); my $inp_root = $inp_tree->getDocumentElement; my $root_text = $inp_root->toString(); $rule_source = "head/node1@attr1"; my @inp_search_nodes = $inp_root->findnodes($rule_source); my $inp_search_results = scalar @inp_search_nodes; if ( 0 == $inp_search_results ) { print "XPath $rule_source not found! \n"; } else { my $path_text = $inp_search_nodes[ 0 ]->findvalue("."); print "Xpath ->: $path_text\n"; my $val = $inp_search_nodes[ 0 ]->textContent(); + print "Value of XPath $rule_source : $val \n"; } [download] If i search for XPath head/node1@attr1 , the code works fine and fetches the value of the node. If i use XPath XPath /head/node1@attr1 , the program gives the error : `"/head/node1 not found!"` If i use the Xpath, i get this error: `Invalid expression` If I use the XPath "/head/node1/@attr1", I get this error: `Invalid expression`	[reply] [d/l] [select]
Re^3: XPath with node names and attributes... by thunders (Priest) on Oct 20, 2009 at 17:04 UTC
Didn't have a chance to test your example, but I think this is the problem: `$rule_source = "head/node1@attr1";` [download] Perl thinks you want to insert the contents of an array called @attr1 into the string because you used double quotes. Since there is no such array your $rule_source ends up with just "head/node1". Either escape the '@' or use a single quoted string as in the examples below: `$rule_source = "head/node1\@attr1"; # or $rule_source = 'head/node1@attr1';` [download]	[reply] [d/l] [select]


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