如何在具有命名空间前缀的TXMLDocument上使用XPath？ [英] How to use XPath on TXMLDocument which has namespace prefixes?

问题描述

我有一个从第三方网络服务器收到的XML数据包：

 <？xml version =1.0 encoding =utf-8？> 
< soap：Envelope xmlns：xsi =http://www.w3.org/2001/XMLSchema-instance
 xmlns：xsd =http://www.w3.org/2001 / XMLSchema
 xmlns：soap =http://schemas.xmlsoap.org/soap/envelope/> 
< soap：Body> 
< SomeResponse xmlns =http：// someurl> 
< SomeResult> 
 ..... 
< / SomeResult> 
< / SomeResponse> 
< / soap：Body> 
< / soap：Envelope> 
  

为了跨平台的能力，这个XML被加载到Delphi的 IXMLDocument ：

  XmlDoc.LoadFromXML（XmlString）; 
  

我是使用解决方案使用XPath查找XML节点。该解决方案在其他情况下起作用，但是当XML文档包含命名空间前缀时，它将失败。

我正在尝试访问路径：

  / soap：Envelope / soap：Body / SomeResponse / SomeResult 
  

从链接的答案：

  function selectNode（xnRoot：IXmlNode; const nodePath：WideString）：IXmlNode ; 
 var 
 intfSelect：IDomNodeSelect; 
 dnResult：IDomNode; 
 intfDocAccess：IXmlDocumentAccess; 
 doc：TXmlDocument; 
 begin 
结果：= nil; 
如果没有分配（xnRoot）或不支持（xnRoot.DOMNode，IDomNodeSelect，intfSelect）然后
退出; 
 dnResult：= intfSelect.selectNode（nodePath）; 
如果分配（dnResult）然后
 begin 
如果支持（xnRoot.OwnerDocument，IXmlDocumentAccess，intfDocAccess）然后
 doc：= intfDocAccess.DocumentObject 
 else 
 doc：= nil; 
结果：= TXmlNode.Create（dnResult，nil，doc）; 
结束
结束
  

它在 dnResult：= intfSelect.selectNode（nodePath） code> with EOleException ：引用未声明的命名空间前缀：'soap'

当节点名称具有命名空间前缀时，如何使其工作？

解决方案

不要尝试在XPath查询中包含命名空间。
如果您想要的是SomeResult节点的文本，那么可以使用// SomeResult作为查询。由于某种原因，默认名称空间 xmlns =http：// someurl上的缺省xml实现（msxml）barfs在 SomeResponse parentnode。然而，使用OmniXML作为DOMVendor（= Crossplatform并且从XE7有效 - 感谢@gabr）这样做：

 程序Project3; 
 
 {$ APPTYPE CONSOLE} 
 
 {$ R * .res} 
 
使用
 Xml.XmlIntf，
 Xml .XMLDoc，
 Xml.XMLDom，
 Xml.omnixmldom，
 System.SysUtils; 
 
 const 
 xml ='<？xml version =1.0encoding =utf-8？>'+＃13＃10 + 
' ：Envelope xmlns：xsi =http://www.w3.org/2001/XMLSchema-instance'+＃13＃10 + 
'xmlns：xsd =http://www.w3.org/ 2001 / XMLSchema'+＃13＃10 + 
'xmlns：soap =http://schemas.xmlsoap.org/soap/envelope/>'+＃13＃10 + 
' < soap：Body>'+＃13＃10 + 
'< SomeResponse xmlns =http://tempuri.org>'+＃13＃10 + 
'< SomeResult> 1< / SomeResult>'+＃13＃10 + 
'< / SomeResponse>'+＃13＃10 + 
'< / soap：Body>'+＃13＃10 + 
'< / soap：Envelope>'; 
 
函数selectNode（xnRoot：IXmlNode; const nodePath：WideString）：IXmlNode; 
 var 
 intfSelect：IDomNodeSelect; 
 dnResult：IDomNode; 
 intfDocAccess：IXmlDocumentAccess; 
 doc：TXmlDocument; 
 begin 
结果：= nil; 
如果没有分配（xnRoot）或不支持（xnRoot.DOMNode，IDomNodeSelect，intfSelect）然后
退出; 
 dnResult：= intfSelect.selectNode（nodePath）; 
如果分配（dnResult）然后
 begin 
如果支持（xnRoot.OwnerDocument，IXmlDocumentAccess，intfDocAccess）然后
 doc：= intfDocAccess.DocumentObject 
 else 
 doc：= nil; 
结果：= TXmlNode.Create（dnResult，nil，doc）; 
结束
结束
 
函数XPathQuery（Doc：IXMLDocument; Query：String）：String; 
 
 var 
节点：IXMLNode; 
 
 begin 
结果：=''; 
 Node：= SelectNode（Doc.DocumentElement，Query）; 
如果分配（Node）然后
结果：= Node.Text 
 end; 
 
 var 
 Doc：IXMLDocument; 
 
 begin 
 DefaultDOMVendor：= sOmniXmlVendor; 
 Doc：= TXMLDocument.Create（nil）; 
 try 
 Doc.LoadFromXML（Xml）; 
 Writeln（Doc.XML.Text）; 
 Writeln（XPathQuery（Doc，'// SomeResult'）））; 
除了
在E：Exception do 
 Writeln（E.ClassName，'：'，E.Message）; 
结束
 Doc：= nil; 
 Readln; 
结束。 
  

I have an XML packet received from a third-party web server:

<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xmlns:xsd="http://www.w3.org/2001/XMLSchema"
  xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
  <soap:Body>
    <SomeResponse xmlns="http://someurl">
      <SomeResult>
        .....
      </SomeResult>
    </SomeResponse>
  </soap:Body>
</soap:Envelope>

To be cross-platform capable, this XML is loaded into Delphi's IXMLDocument:

XmlDoc.LoadFromXML(XmlString);

I'm using a solution to find an XML node using XPath. The solution works in other cases, however when the XML document contains namespace prefixes, it fails.

I'm trying to access path:

/soap:Envelope/soap:Body/SomeResponse/SomeResult

From the linked answer:

function selectNode(xnRoot: IXmlNode; const nodePath: WideString): IXmlNode;
var
  intfSelect : IDomNodeSelect;
  dnResult : IDomNode;
  intfDocAccess : IXmlDocumentAccess;
  doc: TXmlDocument;
begin
  Result := nil;
  if not Assigned(xnRoot) or not Supports(xnRoot.DOMNode, IDomNodeSelect, intfSelect) then
    Exit;
  dnResult := intfSelect.selectNode(nodePath);
  if Assigned(dnResult) then
  begin
    if Supports(xnRoot.OwnerDocument, IXmlDocumentAccess, intfDocAccess) then
      doc := intfDocAccess.DocumentObject
    else
      doc := nil;
    Result := TXmlNode.Create(dnResult, nil, doc);
  end;
end;

It fails at dnResult := intfSelect.selectNode(nodePath); with EOleException: Reference to undeclared namespace prefix: 'soap'

How do I make this work when the node names have a namespace prefix?

解决方案

Do not try to include namespaces in your XPath query. If all you want is the text of the SomeResult node, then you can use '//SomeResult' as query. For some reason the default xml implementation (msxml) barfs on the default namespace xmlns="http://someurl" on the SomeResponse parentnode. However, using OmniXML as the DOMVendor (= Crossplatform and valid from XE7 - thanks to @gabr) this works:

program Project3;

{$APPTYPE CONSOLE}

{$R *.res}

uses
  Xml.XmlIntf,
  Xml.XMLDoc,
  Xml.XMLDom,
  Xml.omnixmldom,
  System.SysUtils;

const
 xml = '<?xml version="1.0" encoding="utf-8"?>'+#13#10+
        '<soap:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"'+#13#10+
        'xmlns:xsd="http://www.w3.org/2001/XMLSchema"'+#13#10+
        'xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">'+#13#10+
        ' <soap:Body>'+#13#10+
        '  <SomeResponse xmlns="http://tempuri.org">'+#13#10+
        '   <SomeResult>1</SomeResult>'+#13#10+
        '  </SomeResponse>'+#13#10+
        ' </soap:Body>'+#13#10+
        '</soap:Envelope>';

function selectNode(xnRoot: IXmlNode; const nodePath: WideString): IXmlNode;
var
  intfSelect : IDomNodeSelect;
  dnResult : IDomNode;
  intfDocAccess : IXmlDocumentAccess;
  doc: TXmlDocument;
begin
  Result := nil;
  if not Assigned(xnRoot) or not Supports(xnRoot.DOMNode, IDomNodeSelect, intfSelect) then
    Exit;
  dnResult := intfSelect.selectNode(nodePath);
  if Assigned(dnResult) then
  begin
    if Supports(xnRoot.OwnerDocument, IXmlDocumentAccess, intfDocAccess) then
      doc := intfDocAccess.DocumentObject
    else
      doc := nil;
    Result := TXmlNode.Create(dnResult, nil, doc);
  end;
end;

function XPathQuery(Doc : IXMLDocument; Query : String) : String;

var
 Node : IXMLNode;

begin
 Result := '';
 Node := SelectNode(Doc.DocumentElement, Query);
 if Assigned(Node) then
  Result := Node.Text
end;

var
 Doc : IXMLDocument;

begin
 DefaultDOMVendor := sOmniXmlVendor;
 Doc := TXMLDocument.Create(nil);
 try
  Doc.LoadFromXML(Xml);
  Writeln(Doc.XML.Text);
  Writeln(XPathQuery(Doc, '//SomeResult'));
 except
  on E: Exception do
   Writeln(E.ClassName, ': ', E.Message);
 end;
 Doc := nil;
 Readln;
end.

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