perl - XPath 表达式使用 XML::LibXML::XPathContext -> findnodes() 返回空节点列表

Question

xml:

<zoo xmlns="http://www.zoo.com" xmlns:xs="http://www.w3.org/2001/XMLSchema-instance" xs:schemaLocation="http://www.zoo.com animali.xsd">

<area id="1" posizione="nord" nome="scimmie">
    <animale>
        <nome>Gigi</nome>
        <sesso>Male</sesso>
        <eta>3</eta>
        <img>../images/Gigi.png</img>
    </animale>

    <animale>
        <nome>Gigia</nome>
        <sesso>Female</sesso>
        <eta>2</eta>
        <img>../images/Gigia.png</img>
    </animale>
</area>

<area id="2" posizione="nord" nome="giraffe">
    <animale>
        <nome>Giro</nome>
        <sesso>Male</sesso>
        <eta>6</eta>
        <img>../images/Giro.png</img>
    </animale>
</area>
<area id="3" posizione="D8" nome="Cammelli"/>
</zoo>

代码:

my $parser = XML::LibXML->new;
my $doc = $parser->parse_file("../xml/animals.xml");
my $root = $doc->getDocumentElement();
my $xpc = XML::LibXML::XPathContext->new;
$xpc->registerNs('zoo', 'http://www.zoo.com');
my $xpath_exp = "//zoo:animale[nome='".$name."']";  #also tried with "Gigi" instead of $name
my $size = $xpc -> findnodes($xpath_exp, $doc)->size();

有了这些 xml 和代码，我总是有 $size = 0

但是如果我尝试不带谓词的 xpath 表达式，例如“//zoo:animale”或“//zoo:animale/nome”

如果我在此 xpath 测试器上尝试相同的表达式(带有谓词): http://www.whitebeam.org/library/guide/TechNotes/xpathtestbed.rhtm ，它有效

有什么问题吗？

Answer 1

"//zoo:animale[nome='".$name."']";

必须:

"//zoo:animale[zoo:nome='".$name."']";