Perl XML::LibXML 从特定节点获取信息

Question

我意识到有很多类似的问题，但我仍然无法找到我正在寻找的具体答案。

我使用 Perl 和 XML::LibXML 库从 XML 文件中读取信息。 XML 文件有许多节点和许多子节点（以及子子节点等）。我试图从“每个节点”的 XML 文件中提取信息，但我真的陷入了困境，试图弄清楚如何做到这一点。

这只是我想要做的一个例子：

#!/usr/bin/perl -w

use XML::LibXML

open ($xml_fh, "<test.xml");
my $dom = XML::LibXML->load_xml(IO => $xml_fh);;
close($xml_fh);

foreach $chapter ($dom->findnodes('/file/chapter')) {
        my $chapterNumber = $chapter->findvalue('@number');
        print "Chapter #$chapterNumber\n";

         #I tried $dom->findnodes('/file/chapter/section') <-- spelling out the xPath with same results..
        foreach $section ($dom->findnodes('//section')) {
                my $sectionNumber = $section->findvalue('@number');
                print " Section #$sectionNumber\n";

                foreach $subsection ($dom->findnodes('//subsection')) {
                        my $subsectionNumber = $subsection->findvalue('@number');
                        print "  SubSection $subsectionNumber\n";
                }
        }
}

这个特定的 XML 文件是这样设置的：

<file>
 <chapter number="1">
  <section number="abc123">
   There is some data here I'd like to get to
   <subsection number="abc123.(s)(4)">
    Some additional data here
    <subsection number="deeperSubSec">
     There might even be deeper subsections
     </subsection>
   </subsection>
  </section>
 </chapter>
 <chapter number="208">
  <section number="dgfj23">
   There is some data here I'd like to get to also
   <subsection number="dgfj23.(s)(4)">
    Some additional data here also
    <subsection number="deeperSubSec44">
     There might even be deeper subsections also
     </subsection>
   </subsection>
  </section>
 </chapter>
<chapter number="998">
  <section number="xxxid">
   There is even more data here I'd like to get to also
   <subsection number="xxxid.(s)(4)">
    Some additional data also here too
    <subsection number="deeperSubSec999">
     There might even be deeper subsections also again
     </subsection>
   </subsection>
  </section>
 </chapter>
</file>

不幸的是，我最终得到的只是重复数据的列表。我确信这是因为我嵌套了 for 循环，但我真的没有掌握关于如何操作这种数据类型的基本理解。希望有人能提供一些资源或见解。

这是我当前的输出：

Chapter #1
 Section #abc123
  SubSection abc123.(s)(4)
  SubSection deeperSubSec
  SubSection dgfj23.(s)(4)
  SubSection deeperSubSec44
  SubSection xxxid.(s)(4)
  SubSection deeperSubSec999
 Section #dgfj23
  SubSection abc123.(s)(4)
  SubSection deeperSubSec
  SubSection dgfj23.(s)(4)
  SubSection deeperSubSec44
  SubSection xxxid.(s)(4)
  SubSection deeperSubSec999
 Section #xxxid
  SubSection abc123.(s)(4)
  SubSection deeperSubSec
  SubSection dgfj23.(s)(4)
  SubSection deeperSubSec44
  SubSection xxxid.(s)(4)
  SubSection deeperSubSec999
Chapter #208
 Section #abc123
  SubSection abc123.(s)(4)
  SubSection deeperSubSec
  SubSection dgfj23.(s)(4)
  SubSection deeperSubSec44
  SubSection xxxid.(s)(4)
  SubSection deeperSubSec999
 Section #dgfj23
  SubSection abc123.(s)(4)
  SubSection deeperSubSec
  SubSection dgfj23.(s)(4)
  SubSection deeperSubSec44
  SubSection xxxid.(s)(4)
  SubSection deeperSubSec999
 Section #xxxid
  SubSection abc123.(s)(4)
  SubSection deeperSubSec
  SubSection dgfj23.(s)(4)
  SubSection deeperSubSec44
  SubSection xxxid.(s)(4)
  SubSection deeperSubSec999
Chapter #998
 Section #abc123
  SubSection abc123.(s)(4)
  SubSection deeperSubSec
  SubSection dgfj23.(s)(4)
  SubSection deeperSubSec44
  SubSection xxxid.(s)(4)
  SubSection deeperSubSec999
 Section #dgfj23
  SubSection abc123.(s)(4)
  SubSection deeperSubSec
  SubSection dgfj23.(s)(4)
  SubSection deeperSubSec44
  SubSection xxxid.(s)(4)
  SubSection deeperSubSec999
 Section #xxxid
  SubSection abc123.(s)(4)
  SubSection deeperSubSec
  SubSection dgfj23.(s)(4)
  SubSection deeperSubSec44
  SubSection xxxid.(s)(4)
  SubSection deeperSubSec999

所以对于每一章，我正在阅读所有部分，然后我正在阅读所有小节等。一遍又一遍..

我想要做的是阅读每一章的相关部分，然后阅读每个部分、相关的小节以及其中的任何适用的小节。

像这样：

Chapter #1
  Section #abc123
    Subsection #abc123.(s)(4
      Sub-Subsection #deeperSubSec
Chapter #208
   Section #dgfj23
    Subsection #dgfj23.(s)(4)
     Sub-Subsection #deeperSubSec44

etc...

此外，最终，在我弄清楚基本操作是如何工作的之后，我需要访问每个章节、部分、小节等中包含的数据。但我认为我需要在跑步之前步行，所以我将首先尝试获取属性的简单值..

感谢您的帮助。

Answer 1

所以我想我想通了。我一直在对包含整个 XML 树的 $dom 对象进行操作。我相信我需要做的是对我正在查看的那块树进行操作，如下所示：

#!/usr/bin/perl -w

use XML::LibXML

open ($xml_fh, "<test.xml");
my $dom = XML::LibXML->load_xml(IO => $xml_fh);;
close($xml_fh);


for $chapter ($dom->findnodes('/file/chapter')) {
        print "Chapter #" . $chapter->findvalue('@number') ."\n";
        foreach $section ($chapter->findnodes('section')) {
                print " Section #" .$section->findvalue('@number') . "\n";
                foreach $subsection ($section->findnodes('subsection')) {
                        print "  Subsection #" . $subsection->findvalue('@number') . "\n";
                }
        }
}

这导致输出更像我希望的：

Chapter #1
 Section #abc123
  Subsection #abc123.(s)(4)
Chapter #208
 Section #dgfj23
  Subsection #dgfj23.(s)(4)
Chapter #998
 Section #xxxid
  Subsection #xxxid.(s)(4)

这是一个更简洁的示例，有助于说明我现在正在处理从我当前所在的上一个循环获得的树的特定部分：

#!/usr/bin/perl -w

use XML::LibXML

open ($xml_fh, "<test.xml");
my $dom = XML::LibXML->load_xml(IO => $xml_fh);;
close($xml_fh);


my @chapters = $dom->findnodes('/file/chapter');

for $chapter (@chapters) {
        my $chapterNo = $chapter->findvalue('@number');
        print "Chpater #$chapterNo\n";

        @sections = $chapter->findnodes('section');
        for $section (@sections) {
                my $sectionNo = $section->findvalue('@number');
                print " Section #$sectionNo\n";

                @subsections = $section->findnodes('subsection');
                for $subsection (@subsections) {
                        my $subsectionNo = $subsection->findvalue('@number');
                        print "  Subsection #$subsectionNo\n";
                }
        }
}