Perl LibXML findvalues(...) 连接值

Question

我正在尝试使用 LibXML 从 XML 文件中提取节点值。当我调用findvalue 时，所有相同元素类型的节点都被连接起来。我对使用 LibXML 完全陌生，而且我对 Perl 不是最敏感的。不幸的是，xml 不是最好的。如何提取单个节点？

下面是示例 XML 和输出。 XML 是来自 iTunes 库导出的 sn-p。

<playlists>
    <dict>
        <key>Name</key><string>Yes - Tales From Topographic Oceans</string>
        <key>Description</key><string></string>
        <key>Playlist ID</key><integer>67312</integer> 
        <key>Playlist Persistent ID</key><string>F28F195257143396</string> 
        <key>All Items</key><true/> 
        <key>Playlist Items</key> 
        <array> 
            <dict>
                <key>Track ID</key><integer>25912</integer>
            </dict>
            <dict>
                <key>Track ID</key><integer>25914</integer>
            </dict>
            <dict>
                <key>Track ID</key><integer>25916</integer>
            </dict>
            <dict>
                <key>Track ID</key><integer>25918</integer>
            </dict>
        </array>
    </dict>
    <dict>
        <key>Name</key><string>Yes - Yessongs</string>
            <key>Description</key><string>Live Album</string>
            <key>Playlist ID</key><integer>67319</integer>
            <key>Playlist Persistent ID</key><string>405B144877D8B8E4</string>
            <key>All Items</key><true/>
            <key>Playlist Items</key>
            <array>
                <dict>
                    <key>Track ID</key><integer>25920</integer>
                </dict>
                <dict>
                    <key>Track ID</key><integer>25922</integer>
                </dict>
                <dict>
                    <key>Track ID</key><integer>25924</integer>
            </dict>

                <dict>
                    <key>Track ID</key><integer>25926</integer>
                </dict>
                <dict>
                    <key>Track ID</key><integer>25928</integer>
                </dict>
                <dict>
                    <key>Track ID</key><integer>25930</integer>
                </dict>
            </array>
    </dict> 
</playlists>

my $dom = XML::LibXML->load_xml(location => $playlistxml);
foreach my $title ($dom->findnodes('//playlists/dict')) {
    my $nodestring = $title->findvalue('./string');
    print $nodestring, "\n";
    foreach my $tracks ($title->findnodes('//playlists/dict/array')) {
        my @trackid = $tracks->findvalue('./dict/integer');
        print @trackid, "\n";
    }
}

这是生成的输出：

Yes - Tales From Topographic OceansF28F195257143396
25912259142591625918
259202592225924259262592825930
Yes - YessongsLive Album405B144877D8B8E4
25912259142591625918
259202592225924259262592825930

期望的输出：

Yes - Tales From Topographic Oceans
25912
25914
25916
25918

Yes - YessongsLive Album
25920
25922
25924
25926
25928
25930

任何帮助将不胜感激

Answer 1

按如下方式更改 XPath：

//playlists/dict        →  /playlists/dict
./string                →  key[text()="Name"]/following-sibling::*[1]
//playlists/dict/array  →  key[text()="Playlist Items"]/following-sibling::*[1]/*
./dict/integer          →  key[text()="Track ID"]/following-sibling::*[1]

是的，那些 XPath 非常混乱，但那是因为我们正在处理一个可怕的架构。

固定：

use strict;
use warnings;
use feature qw( say );

use XML::LibXML qw( );

my $doc = XML::LibXML->load_xml( location => $ARGV[0] );

my @playlist_nodes = $doc->findnodes('/playlists/dict');
for my $playlist_idx (0..$#$playlist_nodes) {
   my $playlist_node = $playlist_nodes->[$playlist_idx];

   say "" if $playlist_idx;

   my $name = $playlist_node->findvalue('key[text()="Name"]/following-sibling::*[1]');
   say $name;

   for my $track_node ($playlist_node->findnodes('key[text()="Playlist Items"]/following-sibling::*[1]/*')) {
      my $id = $track_node->findvalue('key[text()="Track ID"]/following-sibling::*[1]');
      say $id;
   }
}

---

在上面，我提到所使用的架构很糟糕。设计 XML 模式的人被告知要使用 XML，但显然不理解 XML。即使模式对 JSON 等任意数据结构进行编码也是很糟糕的。 （This 会更好。）设计它的人只是为了在使用之前将数据转换为不同的格式。以下是这样做的：

use strict;
use warnings;
use feature qw( say state );

use Carp              qw( croak );
use Types::Serialiser qw( );
use XML::LibXML       qw( );


sub qname {
   my ($node) = @_;
   my $ns   = $node->namespaceURI();
   my $name = $node->nodeName();
   return defined($ns) ? "{$ns}$name" : $name;
}

sub deserialize_array {
   my ($array_node) = @_;
   return [ map { deserialize_value($_) } $array_node->findnodes("*") ];
}

sub deserialize_dict {
   my ($dict_node) = @_;

   my $dict = {};
   my @children = $dict_node->findnodes("*");
   while (@children) {
      my $key_node = shift(@children);
      qname($key_node) eq "key"
         or croak("Expected key");

      my $val_node = shift(@children)
         or croak("Expected value");

      my $key = $key_node->textContent();
      my $val = deserialize_value($val_node);
      $dict->{$key} = $val;
   }

   return $dict;
}

sub deserialize_value {
   my ($val_node) = @_;

   state $deserializers = {
      string  => sub { $_[0]->textContent() },
      integer => sub { 0 + $_[0]->textContent() },
      true    => sub { $Types::Serialiser::true },
      false   => sub { $Types::Serialiser::false },
      array   => \&deserialize_array,
      dict    => \&deserialize_dict,
   };

   my $val_type = qname($val_node);
   my $deserializer = $deserializers->{$val_type}
      or croak("Unrecognized value type \"$val_type\"");

   return $deserializer->($val_node);
}

sub deserialize_doc {
   my ($doc) = @_;
   return deserialize_array($doc->documentElement());
}

有了上述，解决方案变成了以下：

my $doc = XML::LibXML->load_xml( location => $ARGV[0] );
my $playlists = deserialize_doc($doc);

for my $playlist_idx (0..$#$playlists) {
    my $playlist = $playlists->[$playlist_idx];

    say "" if $playlist_idx;

    my $name = $playlist->{"Name"};
    say $name;

    for my $track (@{ $playlist->{"Playlist Items"} }) {
       my $id = $track->{"Track ID"};
       say $id;
    }
}

Answer 2

正如其他发帖者所指出的那样，您的输入数据不容易处理。

使用提供的输入数据示例，您的代码可能如下所示。

use strict;
use warnings;
use feature 'say';

use XML::LibXML;

my $playlistxml = 'playlist.xml';

my $dom = XML::LibXML->load_xml(location => $playlistxml);

foreach my $title ($dom->findnodes('//playlist')) {
    say 'Title: ', $title->findvalue('./title');
    my $tracks = join "\n", map {
        $_->to_literal();
    } $title->findnodes('./tracks/track/@id');
    say $tracks;
    say '';
}

输入数据'playlist.xml'示例

<playlists>
    <playlist id="67312">
        <title>Yes - Tales From Topographic Oceans</title>
        <persistent_id>F28F195257143396</persistent_id> 
        <tracks> 
            <track id="25912" />
            <track id="25914" />
            <track id="25916" />
            <track id="25918" />
        </tracks>
    </playlist>
    <playlist id="67319">
        <title>Yes - Yessongs</title>
        <description>Live Album</description>
        <persistent_id>405B144877D8B8E4</persistent_id>
        <tracks>
            <track id="25920" />
            <track id="25922" />
            <track id="25924" />
            <track id="25926" />
            <track id="25928" />
            <track id="25930" />
        </tracks>
    </playlist> 
</playlists>

输出

Title: Yes - Tales From Topographic Oceans
25912
25914
25916
25918

Title: Yes - Yessongs
25920
25922
25924
25926
25928
25930