XML：仅获取节点的一些子节点

Posted 2023-02-24

【中文标题】XML：仅获取节点的一些子节点

【英文标题】：XML: Get only some child nodes of a node

【发布时间】：2019-04-30 03:52:45

【问题描述】：

我想将下面 xml 中的两个会话作为两个单独的节点进行遍历：

abc.xml：

<?xml version="1.0" encoding="UTF-8"?> 
<resource>    
<session>
     <parameter name="QWS" value="N1"/> 
     <parameter name="AQC" value="Y2"/>
     <parameter name="VDF" value="301"/>
     <parameter name="VTT" value="X2"/>
     <parameter name="HRR" value="Y2"/>
 </session>
 <session>
    <parameter name="ABC" value="N"/> 
     <parameter name="XYZ" value="Y"/>
     <parameter name="GHI" value="30"/>
     <parameter name="DEF" value="X"/>
     <parameter name="QQW" value="Y"/>  
    </session> 
</resource>

但是，当我运行此代码时，它会遍历两个会话：

#!/usr/bin/perl
use warnings;
use strict;
use XML::LibXML;

my $filename = 'E:/perl_files/abc.xml';
my $dom = XML::LibXML->load_xml(location => $filename);

foreach my $session ($dom->findnodes('//session'))

    print "In SESSION \n";
    foreach my $parameter ($session->findnodes('//parameter')) 
        my $name= $parameter->getAttribute('name');
        my $value= $parameter->getAttribute('value');
        print "Tag in session is $name with value $value\n";
    
    print "END OF SESSION\n";   

留下这个输出：

In SESSION
Tag in session is QWS with value N1
Tag in session is AQC with value Y2
Tag in session is VDF with value 301
Tag in session is VTT with value X2
Tag in session is HRR with value Y2
Tag in session is ABC with value N
Tag in session is XYZ with value Y
Tag in session is GHI with value 30
Tag in session is DEF with value X
Tag in session is QQW with value Y
END OF SESSION
In SESSION
Tag in session is QWS with value N1
Tag in session is AQC with value Y2
Tag in session is VDF with value 301
Tag in session is VTT with value X2
Tag in session is HRR with value Y2
Tag in session is ABC with value N
Tag in session is XYZ with value Y
Tag in session is GHI with value 30
Tag in session is DEF with value X
Tag in session is QQW with value Y
END OF SESSION

我希望输出是

In SESSION
Tag in session is QWS with value N1
Tag in session is AQC with value Y2
Tag in session is VDF with value 301
Tag in session is VTT with value X2
Tag in session is HRR with value Y2
END OF SESSION
In SESSION
Tag in session is ABC with value N
Tag in session is XYZ with value Y
Tag in session is GHI with value 30
Tag in session is DEF with value X
Tag in session is QQW with value Y
END OF SESSION

我正在使用 XML::LibXML。 我可以进行哪些更改以每次仅获取一个会话的子节点？ 我看到了使用 childNodes() 的答案，但这会返回一个列表，我不想使用 grep 来查找特定节点。

【参考方案1】：

//parameter到处搜索parameter，只需要在session下搜索，即当前节点下：

    foreach my $parameter ($session->findnodes('.//parameter')) 

【讨论】：

工作就像一个魅力！非常感谢！

【参考方案2】：

//parameter

简称

/descendant::parameter

表示根节点 (/) 的后代名为 parameter，但您想获取上下文节点的后代。为此，你想要

descendant::parameter

也可以写成

.//parameter

问题是，parameter 是会话的孩子，所以你真正想要的只是

child::parameter

也可以写成

parameter

---

最终代码：

#!/usr/bin/perl
use warnings;
use strict;
use XML::LibXML;

my $filename = 'E:/perl_files/abc.xml';
my $dom = XML::LibXML->load_xml(location => $filename);

foreach my $session ($dom->findnodes('/resource/session'))         # <---

    print "In SESSION \n";
    foreach my $parameter ($session->findnodes('parameter'))      # <---
        my $name= $parameter->getAttribute('name');
        my $value= $parameter->getAttribute('value');
        print "Tag in session is $name with value $value\n";
    
    print "END OF SESSION\n";