如何在Perl中从XML :: LibXML访问属性和元素? [英] How can I access attributes and elements from XML::LibXML in Perl?

问题描述

我在使用 XML :: LibXML 包中的名称空间时难以理解/使用名称空间Perl.我可以成功访问元素，但不能访问属性.我有以下代码可以访问XML文件( http://pastebin.com/f3fb9d1d0 ).

I am having trouble understanding / using name spaces with XML::LibXML package in Perl. I can access an element successfully but not an attribute. I have the following code which accesses an XML file (http://pastebin.com/f3fb9d1d0).

my $tree = $parser->parse_file($file); # parses the file contents into the new libXML object.
my $xpc = XML::LibXML::XPathContext->new($tree); 
$xpc->registerNs(microplateML => 'http://moleculardevices.com/microplateML');   

然后我尝试访问一个名为common-name的元素和一个名为name的属性.

I then try and access an element called common-name and an attribute called name.

foreach my $camelid ($xpc->findnodes('//microplateML:species')) {
  my $latin_name = $camelid->findvalue('@name');   
  my $common_name = $camelid->findvalue('common-name');  
  print "$latin_name, $common_name" ;
}

但是仅打印拉丁文名称(@name)，而不是普通名称.我在做什么错?我如何也可以打印出通用名称?

But only the latin-name (@name) is printing out, the common-name is not. What am I doing wrong and how can I get the common-name to print out as well?

在这种情况下，@name是做什么的?我假设它是一个数组，应该将属性放入一个数组中，因为可以有多个属性，但是元素(如common-name)不应该是因为应该只有一个?

What does the @name do in this case? I presume it is an array, and that attributes should be put into an array as there can be more than one, but elements (like common-name) should not be because there should just be one?

我一直在关注以下示例: http ://www.xml.com/pub/a/2001/11/14/xml-libxml.html 此处: http://perl-xml.sourceforge.net/faq/#namespaces_xpath，并尝试使其示例骆驼脚本与我的名称空间配合使用，从而使名称空间变得怪异.

I've been following the examples here: http://www.xml.com/pub/a/2001/11/14/xml-libxml.html and here: http://perl-xml.sourceforge.net/faq/#namespaces_xpath, and trying to get their example camel script working with my namespace, hence the weird namespace.

推荐答案

确保您的XML文件有效，然后使用$node->getAttribute("someAttribute")访问属性.

Make sure you XML file is valid then use $node->getAttribute("someAttribute") to access attributes.

@name是属性名称.您可以在findnodes()中使用它来指定具有给定属性集的元素.例如.像这样的路径:

@name is a attribute name. You'd use it in findnodes() to specify elements with a given attribute set. Eg. a path like:

//camelids/species[@name="Camelus bactrianus"]/

这是一个简单/人为的示例:

Here is a simple/contrived example:

#!/usr/bin/perl -w
use XML::LibXML;

my $parser = XML::LibXML->new();
my $doc = $parser->parse_file('/Users/castle/Desktop/animal.xml');

my $xc = XML::LibXML::XPathContext->new( $doc->documentElement()  );
$xc->registerNs('ns', 'http://moleculardevices.com/microplateML');

my @n = $xc->findnodes('//ns:species');
foreach $nod (@n) {
    print "A: ".$nod->getAttribute("name")."\n";

    my @c = $xc->findnodes("./ns:common-name", $nod);
    foreach $cod (@c) {
        print "B: ".$cod->nodeName;
        print " = ";
        print $cod->getFirstChild()->getData()."\n";
    }
}

输出为:

perl ./xmltest.pl 
A: Camelus bactrianus
B: common-name = Bactrian Camel

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