無法獲取perl中XPath上下文中元素的值

Question

雖然它獲取其他屬性的值，但我無法獲取chapter_title的值。我已經展示了xml的結構。

use XML::LibXML; 

my %chapter_columns = 
(
'Book_Id' => 'substring-before(@id,"ch")', 
'Chapter_Doi' => 'book:meta/@doi', 
'Chapter_Id' => '@id', 
'Chapter_Title' => 'book:locator[contains(@xlink:href, "format=epub")]/@xlink:title', 
'Chapter_Doi_Prefix' => 'substring-before(book:meta/@doi,"/")', 
); 

my $parser = XML::LibXML->new(); 
my $dom = $parser->parse_file("book.xml"); 
my $root = $dom->documentElement(); 
my $xpc = XML::LibXML::XPathContext->new($root); 

$xpc->registerNs('book', 'http://api.abc.org/Book/1.0/'); 
$xpc->registerNs('xlink', 'http://www.w3.org/1999/xlink'); 

foreach my $chapter_node ($xpc->findnodes('/book:bookResource/book:book/ 
book:contents/book:chapter')) 
{ 
foreach my $col(qw/Chapter_Id Chapter_Title Book_Id Chapter_Doi Chapter_Doi_Prefix 
Chapter_Id/) 
{ 
print $chapter_node->findvalue($chapter_columns{$col}), "\n"; 
} 
} 

的「是book.xml」文件的結構如下：

<book:bookResource xmlns:book="http://api.abc.org/Book/1.0/" 
xmlns:xlink="http://www.w3.org/1999/xlink"> 
<book:book> 
<book:contents> 
<book:chapter id="bk111111ch3" type="CHAPTER"> 
<book:locator xlink:href="/book/isbn/979-0-1234-1111-1/book-part/chapter/bk111111ch3? 
releaseStatus=UNRELEASED" xlink:title="Statics" xlink:type="locator" 
xmlns:xlink="http://www.w3.org/1999/xlink"/> 
<book:locator xlink:href="/book/isbn/979-0-1234-1111-1/book-part/chapter/bk111111ch3? 
releaseStatus=UNRELEASED&amp;format=pdf" xlink:title="Statics" xlink:type="locator" 
xmlns:xlink="http://www.w3.org/1999/xlink"/> 
<book:locator xlink:href="/book/isbn/979-0-1234-1111-1/book-part/chapter/bk111111ch3? 
releaseStatus=UNRELEASED&amp;format=epub" xlink:title="Statics" xlink:type="locator" 
xmlns:xlink="http://www.w3.org/1999/xlink"/> 
<book:meta doi="10.1088/bk111111ch3" firstPage="3-1" lastPage="3-22"></book:meta> 
</book:chapter> 
</book:contents> 
</book:book> 
</book:bookResource> 

我不知道是什麼原因導致其無法獲得的價值。任何幫助將是可觀的。對不起，xml的某些部分丟失了。

<book:bookResource xmlns:book="http://api.abc.org/Book/1.0/"> 
<book:book> 
<book:locator xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="/book/isbn/979-0- 
4444-1000-17?releaseStatus=RELEASED" xlink:title="979-0-4444-1000-17" 
xlink:type="locator"> 
</book:locator> 
<book:contents> 
<book:chapter id="bk444444ch1" type="CHAPTER"> 
<book:locator xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="/book/isbn/979-0- 
4444-1000-17/book-part/chapter/bk444444ch1?releaseStatus=RELEASED" 
xlink:role="http://www.abc.org/roles/book-part-locator" xlink:title="Photonic" xlink:type="locator"></book:locator> 
<book:locator xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="/book/isbn/979-0- 
4444-1000-17/book-part/chapter/bk444444ch1?releaseStatus=RELEASED&amp;format=pdf" 
xlink:role="http://www.abc.org/roles/book-part-pdf-locator" xlink:title="Photonic" 
xlink:type="locator"></book:locator> 
<book:locator xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="/book/isbn/979-0- 
4444-1000-17/book-part/chapter/bk444444ch1?releaseStatus=RELEASED&amp;format=epub" 
xlink:role="http://www.abc.org/roles/book-part-epub-locator" xlink:title="Photonic" 
xlink:type="locator"></book:locator> 
<book:meta doi="10.1088/bk444444ch1" firstPage="1-1" lastPage="1-118"> 
<book:author givenName="J E" surname="Field"> 
<book:affiliation xmlns:xlink="http://www.w3.org/1999/xlink" 
xlink:href="bk444444ch1af1" 
xlink:role="http://www.abc.org/roles/affiliation-locator" xlink:type="locator"> 
</book:affiliation> 
</book:author> 
</book:meta> 
</book:chapter> 
</book:contents> 
</book:book> 
</book:bookResource> 

以及確切的錯誤我得到的是

的XPath錯誤：未定義命名空間前綴 錯誤：xmlXPathCompOpEval：參數錯誤 錯誤：xmlXPathCompiledEval：1對象留在堆棧中。

Answer 1

你沒有使用XPC，所以它不知道你的路徑中的xlink意味着什麼。

print $chapter_node->findvalue($chapter_columns{$col}), "\n"; 

應該

print $xpc->findvalue($chapter_columns{$col}, $chapter_node), "\n";