PerlXML::LibXML，findnodes只能读取XML文件的根

Question

我正在尝试解析这个.kml文件：

<?xml version="1.0" encoding="utf-8" ?>
<kml xmlns="http://www.opengis.net/kml/2.2">
<Document id="root_doc">
<Schema name="PostalCodeCanada" id="PostalCodeCanada">
    <SimpleField name="ZIP" type="string"></SimpleField>
    <SimpleField name="VERTICES" type="int"></SimpleField>
</Schema>
<Folder><name>PostalCodeCanada</name>
  <Placemark>
    <Style><LineStyle><color>ff0000ff</color></LineStyle><PolyStyle><fill>0</fill></PolyStyle></Style>
    <ExtendedData><SchemaData schemaUrl="#PostalCodeCanada">
        <SimpleData name="ZIP">G1Y1B1</SimpleData>
        <SimpleData name="VERTICES">5</SimpleData>
    </SchemaData></ExtendedData>
      <Polygon><altitudeMode>relativeToGround</altitudeMode><outerBoundaryIs><LinearRing><altitudeMode>relativeToGround</altitudeMode><coordinates>-73.604399,45.545611 -73.603988,45.545886 -73.602861,45.547715 -73.602861,45.547715 -73.604399,45.545611 -73.604399,45.545611</coordinates></LinearRing></outerBoundaryIs></Polygon>
  </Placemark>
  <Placemark>
    <Style><LineStyle><color>ff0000ff</color></LineStyle><PolyStyle><fill>0</fill></PolyStyle></Style>
    <ExtendedData><SchemaData schemaUrl="#PostalCodeCanada">
        <SimpleData name="ZIP">G1Y1B2</SimpleData>
        <SimpleData name="VERTICES">5</SimpleData>
    </SchemaData></ExtendedData>
      <Polygon><altitudeMode>relativeToGround</altitudeMode><outerBoundaryIs><LinearRing><altitudeMode>relativeToGround</altitudeMode><coordinates>-73.604399,45.545611 -73.603988,45.545886 -73.602861,45.547715 -73.602861,45.547715 -73.604399,45.545611 -73.604399,45.545611</coordinates></LinearRing></outerBoundaryIs></Polygon>
  </Placemark>
</Folder>
</Document></kml>

我将Perl与XML:：LibXML一起使用，但findnodes不能读取除"/"之外的任何节点。这是我的代码：

#!/usr/bin/env perl
use XML::LibXML;
use strict;
use warnings;
my $outputFilename = "PostalCodesCollegePro.kml";
my $intro = '<?xml version="1.0" encoding="utf-8" ?>'."n".'<kml xmlns="http://www.opengis.net/kml/2.2">'."n".'<Document id="root_doc">'."n".'<Schema name="PostalCodeCanada" id="PostalCodeCanada">'."nt".'<SimpleField name="ZIP" type="string"></SimpleField>'."nt".'<SimpleField name="VERTICES" type="int"></SimpleField>'."n".'</Schema>'."n".'<Folder><name>PostalCodeCanada</name>'."n";
my $outro = '</Folder>'."n".'</Document></kml>'."n";
open (my $fh, ">".$outputFilename) or die "Impossible d'ouvrir le fichier d'écriture";
print $fh $intro;
my $xml = XML::LibXML->new();
my $data = $xml->parse_file("PostalCodeCanada.kml");
foreach my $node ( $data->findnodes('//Folder') ) {
    print ($node->toString);
#   my($zip) = $node->findnodes('./ExtendedData/SchemaData/SimpleData');
#   print ($zip->to_literal."n");
#   if ($zip->to_literal =~ /(^G1Y)|(^G3A)|(^G2G)|(^G3L)|(^G3H)|G0A2R0|G0A1T0|G0A1L0|G0A3H0|G0A3G0|G0A2Y0|G0A2Z0|G0A4N0|G0A2J0|G0A3M0|G0A4A0|G0A1A0|G0A1Y0|G0A1S0|G0A4B0|G0A3T0|G0A3B0|G0A4H0|G0A1W0|G0A3L0|G0A4L0|G0A3A0/){
#       print $fh $node->to_literal;
#   }
}
print $fh $outro; 
close $fh or warn "Impossible de fermer le fichier après écriture";`

感谢所有愿意提供帮助的人！附言：这是一个缩小的.kml文件，事实上，真正的文件包含了所有加拿大邮政编码的所有地理信息。我正在尝试生成另一个仅包含所需邮政编码的.kml，以便使用GoogleMapneneneba API生成地图。

Answer 1

您的问题是您的节点都在一个名称空间内，因此需要处理这个问题。最简单的方法可能是使用XML:：LibXML:：XPathContext对象。

my $xml = XML::LibXML->new();
my $data = $xml->parse_file("PostalCodeCanada.kml");
my $xpc = XML::LibXML::XPathContext->new($data);
$xpc->registerNs('k', 'http://www.opengis.net/kml/2.2');
foreach my $node ( $xpc->findnodes('//k:Folder') ) {
  ...
}

Answer 2

您的XML数据使用默认名称空间，当您使用XPath访问它时，必须显式指定该名称空间。对于XML::LibXML，这意味着您必须创建一个XML::LibXML::XPathContext对象来搜索数据

下面是一个示例程序，它可以满足您的需求

#!/usr/bin/env perl
use strict;
use warnings;
use XML::LibXML;
my $doc = XML::LibXML->load_xml(location => 'PostalCodeCanada.kml');
my $xpc = XML::LibXML::XPathContext->new($doc);
$xpc->registerNs( gis => 'http://www.opengis.net/kml/2.2');
for my $folder ( $xpc->findnodes('/gis:kml/gis:Document/gis:Folder') ) {
    my ($zip) = $xpc->findnodes('gis:Placemark/gis:ExtendedData/gis:SchemaData/gis:SimpleData', $folder);
    $zip = $zip->to_literal;
    print "$zipn";
    if ( $zip =~ /(?:G0A(?:1A0|1L0|1S0|1T0|1W0|1Y0|2J0|2R0|2Y0|2Z0|3A0|3B0|3G0|3H0|3L0|3M0|3T0|4A0|4B0|4H0|4L0|4N0)|G1Y|G1Y1B1|G2G|G3A|G3H|G3L)/){
        print $folder->to_literal;
    }
}

Answer 3

您已经有了来自XML::LibXML的答案。但是我要指出的是，如果使用XML::Twig，则可以忽略名称空间。（这是因为它并不真正支持它们——如果你只有一个，那也没关系！）

#!/usr/bin/env perl
use strict;
use warnings;
use XML::Twig;
my $twig = XML::Twig -> new -> parsefile ( 'input.kml');
foreach my $node ( $twig -> findnodes ( '//Folder') ) {
   print $node -> text,"n";
}