c# - 如何解析 XSL 包含在从字符串加载 XSL 的转换中？

Question

.NET 2.0/VS2005

我正在尝试使用 XslCompiledTransform类来执行 XSL 转换。我有两个 XSL 文件，第一个文件以 <xsl:include> 的形式包含对另一个文件的引用。声明:

主.xsl:

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:include href="Included.xsl" />
  ...
  ...
</xsl:stylesheet>

现在，如果我可以将“Main.xsl”文件本身作为 URI 加载，我的转换代码将非常简单:

// This is a function that works. For demo only.
private string Transform(string xslFileURI)
{
  XslCompiledTransform xslt = new XslCompiledTransform();

  // This load works just fine, if I provide the path to "Main.xsl".
  // The xsl:include is automatically resolved.
  xslTransform.Load(xslFileURI);

  StringWriter sw = new StringWriter();
  xslt.Transform(Server.MapPath("~/XML/input.xml"), null, sw);
  return sw.ToString();
}

问题是我收到 Main.xsl 文件的内容作为一个字符串，并且需要将该字符串作为 XmlReader/IXpathNavigable 加载. 此时这是必要的限制。当我尝试使用 XmlReader/XpathDocument 执行相同操作时，它失败了，因为代码在 C:\Program Files\Microsoft Visual Studio 8\Common7\IDE\ 中查找“Included.xsl”文件夹!显然，XmlResolver无法解析相对 URL，因为它只接收一个字符串作为输入 XSL。

我在这个方向上的努力是这样的:

// This doesn't work! Halp!
private string Transform(string xslContents)
{
  XslCompiledTransform xslt = new XslCompiledTransform();
  XmlUrlResolver resolver = new XmlUrlResolver();
  resolver.Credentials = CredentialCache.DefaultCredentials;

  //METHOD 1: This method does not work.
  XmlReaderSettings settings = new XmlReaderSettings();
  settings.XmlResolver = resolver;
  XmlReader xR = XmlReader.Create(new StringReader(xslContents), settings);
  xslt.Load(xR);    // fails

  // METHOD 2: Does not work either.
  XPathDocument xpDoc = new XPathDocument(new StringReader(xslContents));
  xslt.Load(xpDoc, new XsltSettings(true, true), resolver);  //fails.

  StringWriter sw = new StringWriter();
  xslt.Transform(Server.MapPath("~/XML/input.xml"), null, sw);
  return sw.ToString();
}

我尝试使用 ResolveUri XmlUrlResolver 的方法获取 Stream引用要包含的 XSL 文件，但对如何使用此 Stream 感到困惑。 IOW，我怎么告诉 XslCompiledTransform除了 Main.xsl XmlReader 之外还使用此流的对象:

Uri mainURI = new Uri(Request.PhysicalApplicationPath + "Main.xsl");
Uri uri = resolver.ResolveUri(mainURI, "Included.xsl");

// I can verify that the Included.xsl file loads in the Stream below.
Stream s = resolver.GetEntity(uri, null, typeof(Stream)) as Stream;

// How do I use this Stream in the function above??

任何帮助是极大的赞赏。很抱歉发了这么长的帖子!

供您引用，Exception StackTrace 如下所示:

[FileNotFoundException: Could not find file 'C:\Program Files\Microsoft Visual Studio 8\Common7\IDE\Included.xsl'.]
   System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath) +328
   System.IO.FileStream.Init(String path, FileMode mode, FileAccess access, Int32 rights, Boolean useRights, FileShare share, Int32 bufferSize, FileOptions options, SECURITY_ATTRIBUTES secAttrs, String msgPath, Boolean bFromProxy) +1038
   System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize) +113
   System.Xml.XmlDownloadManager.GetStream(Uri uri, ICredentials credentials) +78
   System.Xml.XmlUrlResolver.GetEntity(Uri absoluteUri, String role, Type ofObjectToReturn) +51
   System.Xml.Xsl.Xslt.XsltLoader.CreateReader(Uri uri, XmlResolver xmlResolver) +22
   System.Xml.Xsl.Xslt.XsltLoader.LoadStylesheet(Uri uri, Boolean include) +33
   System.Xml.Xsl.Xslt.XsltLoader.LoadInclude() +349
   System.Xml.Xsl.Xslt.XsltLoader.LoadRealStylesheet() +704
   System.Xml.Xsl.Xslt.XsltLoader.LoadDocument() +293
   System.Xml.Xsl.Xslt.XsltLoader.LoadStylesheet(XmlReader reader, Boolean include) +173

Answer 1

使用自定义的 XmlUrlResolver

class MyXmlUrlResolver : XmlUrlResolver
    {
        public override Uri ResolveUri(Uri baseUri, string relativeUri)
        {
            if (baseUri != null)
                return base.ResolveUri(baseUri, relativeUri);
            else
                return base.ResolveUri(new Uri("http://mypath/"), relativeUri);
        }
    }

并在XslCompiledTransform的加载函数中使用它，

resolver=new MyXmlUrlResolver();
xslt.Load(xR,null,resolver);