的Perl和XPath：考虑层次

Question

我想提取XML的属性值考虑层级：

<?xml version="1.0" encoding="UTF-8"?> 
<database> 
    <row1s> 
    <row1 name="fox" category="mammal"> 
     <row2s> 
     <row2 type="1"/> 
     <row2 type="2"/> 
     </row2s> 
    </row1> 
    <row1 name="horse" category="mammal"> 
     <row2s> 
     <row2 type="3"/> 
     </row2s> 
    </row1> 
    <row1 name="bee" category="insect"> 
     <row2s/> 
    </row1> 
    <row1 name="wasp" category="insect"> 
     <row2s/> 
    </row1> 
    </row1s> 
</database> 

这是Perl代码我提取值：

use strict; 
use DBI; 
use XML::XPath; 
use XML::XPath::XMLParser; 

my $xrow1; 
my $xrow2; 

my $xp = XML::XPath->new (filename => "animals3.xml"); 

my $node_list1 = $xp->find ("//row1s/row1"); 

foreach my $row1 ($node_list1->get_nodelist()) { 
    $xrow1 = $row1->getAttribute("name"); 
    print "Level row1 gives: $xrow1\n"; 

    my $node_list2 = $xp->find ("//row2s/row2"); 

    foreach my $row2 ($node_list2->get_nodelist()) { 
    $xrow2 = $row2->getAttribute("type");  
    print "Level row2 gives: $xrow2\n"; 
    } 
} 

我得到的是：

Level row1 gives: fox 
Level row2 gives: 1 
Level row2 gives: 2 
Level row2 gives: 3 
Level row1 gives: horse 
Level row2 gives: 1 
Level row2 gives: 2 
Level row2 gives: 3 
Level row1 gives: bee 
Level row2 gives: 1 
Level row2 gives: 2 
Level row2 gives: 3 
Level row1 gives: wasp 
Level row2 gives: 1 
Level row2 gives: 2 
Level row2 gives: 3 

对于每个级别1，我从级别2获得所有属性值。这不是什么iw蚂蚁。我想只输出correpondent级别1的水平2项，但我要的是：

Level row1 gives: fox 
Level row2 gives: 1 
Level row2 gives: 2 
Level row1 gives: horse 
Level row2 gives: 3 
Level row1 gives: bee 
Level row1 gives: wasp 

我将不胜感激任何提示如何解决这个问题。

谢谢。

Answer 1

领先/表示绝对路径。

my $node2 = $xp->find("//row2s/row2"); 

应该

my $node2 = $xp->find("row2s/row2", $row1); 

---

评论：

• 无论$node1也不$node2是节点。选择更好的名字。

• 声明你所做的变量部分无视声明它们的目的。他们应该在适当的循环中声明。

Answer 2

下修复和简化你的脚本：

use strict; 
use warnings; 

use XML::XPath; 
use XML::XPath::XMLParser; 

#my $xp = XML::XPath->new(filename => "animals3.xml"); 
my $xp = XML::XPath->new(ioref => \*DATA); 

for my $row1 ($xp->findnodes('//row1s/row1')){ 
    printf "Level row1 gives: %s\n", $row1->getAttribute("name"); 

    for my $row2 ($row1->findnodes('.//row2s/row2')) { 
     printf "Level row2 gives: %s\n", $row2->getAttribute("type"); 
    } 
} 

__DATA__ 
<?xml version="1.0" encoding="UTF-8"?> 
<database> 
    <row1s> 
    <row1 name="fox" category="mammal"> 
     <row2s> 
     <row2 type="1"/> 
     <row2 type="2"/> 
     </row2s> 
    </row1> 
    <row1 name="horse" category="mammal"> 
     <row2s> 
     <row2 type="3"/> 
     </row2s> 
    </row1> 
    <row1 name="bee" category="insect"> 
     <row2s/> 
    </row1> 
    <row1 name="wasp" category="insect"> 
     <row2s/> 
    </row1> 
    </row1s> 
</database> 

输出：

Level row1 gives: fox 
Level row2 gives: 1 
Level row2 gives: 2 
Level row1 gives: horse 
Level row2 gives: 3 
Level row1 gives: bee 
Level row1 gives: wasp