Delphi / MSXML：XPath查询失败 [英] Delphi/MSXML: XPath queries fail

问题描述

我已经加载了一个XML文档，现在我希望运行一个XPath查询来选择XML的某个子集。 XML是

 <？xml version =1.0？> 
< catalog xmlns：xsi ='http：//www.w3.org/2001/XMLSchema-instance'> 
< book id =bk101> 
< author> Gambardella，Matthew< / author> 
< title> XML开发人员指南< / title> 
< genre> Computer< / genre> 
< price> 44.95< / price> 
< publish_date> 2000-10-01< / publish_date> 
< description>深入了解使用
 XML创建应用程序。< / description> 
< / book> 
< / catalog> 
  

，过程类似于

  procedure RunXPathQuery（XML：IXMLDOMDocument2; Query：string）; 
 begin 
 
 XML.setProperty（'SelectionLanguage'，'XPath'）; 
 
 NodeListResult：= XML.documentElement.selectNodes（Query））; 
 
 ShowMessage（'Found（'+ IntToStr（NodeListResult.length）+'）nodes）'）; 
 
 end; 
  

问题是：当我为上述XML运行XPath查询'/ catalog'时，它返回如预期）一个元素的一个元素。但是，如果我从
< catalog xmlns：xsi ='http：//www.w3.org/2001中删除：xsi / XMLSchema-instance'> ，并重新运行查询，返回的模板器为空。如果我删除了整个xmlns属性，则生成的nodelist再次有1个元素。所以我的问题是这样的：我该如何解决这个问题，即如何让MSXML返回正确数量的实例（运行XPath查询时），不管的命名空间（或其他属性）？

谢谢！

解决方案

请参阅此链接！

当您使用< catalog xmlns ='http：//www.w3.org/2001/XMLSchema-instance'> 时，整个节点将被移动到一个不同的（默认）命名空间。你的XPath没有看到这个其他命名空间，所以它找不到任何数据。使用< catalog xmlns：xsi ='http：//www.w3.org/2001/XMLSchema-instance'> 你只是将xsi声明为不同的命名空间。这将是与默认命名空间不同的命名空间。

我现在无法测试，但添加一些像这样可能有帮助：

  XML.setProperty（'SelectionNamespaces'，'xmlns =''http：//www.w3.org/2001/XMLSchema-instance'''）; 
  

或者也许没有。正如我所说，我现在不能测试。

I've loaded a XML document, and now I wish to run a XPath query to select a certain subset of the XML. The XML is

<?xml version="1.0"?>
<catalog xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance'>
   <book id="bk101">
      <author>Gambardella, Matthew</author>
      <title>XML Developer's Guide</title>
      <genre>Computer</genre>
      <price>44.95</price>
      <publish_date>2000-10-01</publish_date>
      <description>An in-depth look at creating applications with
      XML.</description>
   </book>
</catalog>

and the procedure goes something like

procedure RunXPathQuery(XML: IXMLDOMDocument2; Query: string);
begin

  XML.setProperty('SelectionLanguage', 'XPath');

  NodeListResult := XML.documentElement.selectNodes(Query));

  ShowMessage('Found (' + IntToStr(NodeListResult.length) + ') nodes.');

end;

Problem is: when I run the XPath query '/catalog' for the above XML, it returns (as expected) a nodelist of 1 element. However, if I remove :xsi from <catalog xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance'> and re-run the query, the nodelist returned is empty. If I remove the entire 'xmlns'-attribute, the resulting nodelist has, once again, 1 element.

So my question is this: what can I do to remedy this, i.e. how do I make MSXML return the correct number of instances (when running a XPath query), regardless of the namespace (or other attributes)?

Thanks!

解决方案

See this link!

When you use <catalog xmlns='http://www.w3.org/2001/XMLSchema-instance'> then the whole node will be moved to a different (default) namespace. Your XPath isn't looking inside this other namespace so it can't find any data. With <catalog xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance'> you're just declaring xsi as a different namespace. This would be a different namespace than the default namespace.

I can't test it right now but adding something like this might help:

XML.setProperty('SelectionNamespaces', 'xmlns=''http://www.w3.org/2001/XMLSchema-instance''');

Or maybe it doesn't. As I said, I can't test it right now.

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