实例简析XPath串函数和XSLT

XPath(xml Path language)是一种处理XML文档段的语言。XSLT(Extensible Stylesheet Language Transformations,可扩展样式表语言转换)使用XPath描述表达式和地址路径控制节点选取。XSLT可以将XML转换为各种格式，如HTML或其他格式。
下面用一个邮件合并程序来简要说明XPath的串函数。下面的XML文件中包含数据，XSLT文件中包含对邮件格式的定义。MSXML4.0对XML文档应用样式表，产生一个合并的邮件文本文档。
XML文件 Letter.xml

<?xml version="1.0" encoding="UTF-8"?><Letter>  <Date>July 17, 2002</Date>  <To>     <FirstName>Vicky</FirstName>     <LastName>P</LastName>     <Sex>Male</Sex>  </To>  <Address>     <Line1>900 National Pkwy</Line1>     <Line2>Suite 105</Line2>     <City>Bellevue</City>     <State>WA</State>     <Zip>98007</Zip>     <Country>USA</Country>  </Address>  <Subject>ESTATE OF JOHN DOE / FILE NO. 12345.6789</Subject>  <Text>     Please pay the PRoperty taxes as soon as possible.  </Text>  <Sender>     <FirstName>John</FirstName>     <LastName>M</LastName>     <Title>Sr. Tax Consultant</Title>  </Sender></Letter>

XSLT样式表文档 Letter.xsl

<?xml version='1.0' encoding="utf-8"?><xsl:stylesheet version="1.0"      xmlns:xsl="http://www.w3.org/1999/XSL/Transform"><xsl:output method="text" indent="yes"/><xsl:variable name="NL" select="'&#xA;'" /><xsl:variable name="Para" select="concat($NL, $NL)" /><xsl:template match="/">   <xsl:value-of select="//Date" />   <xsl:value-of select="$Para" />To,<xsl:value-of select="concat(//To/FirstName, ' ', //To/LastName)" /><xsl:value-of select="$NL" /><xsl:value-of select="//Address/Line1" /><xsl:value-of select="$NL" /><xsl:value-of select="//Address/Line2" /><xsl:value-of select="$NL" /><xsl:value-of select="concat(//Address/City, ' ', //Address/State, ' ', //Address/Zip)" /><xsl:value-of select="$NL" /><xsl:value-of select="//Address/Country" /><xsl:value-of select="$Para" />Regarding: <xsl:value-of select="//Subject" /><xsl:value-of select="$NL" />Dear <xsl:if test="starts-with(//Sex, 'M')">Mr. </xsl:if><xsl:if test="starts-with(//Sex, 'F')">Miss </xsl:if><xsl:value-of select="concat(//To/FirstName, ' ', //To/LastName)" />,<xsl:value-of select="$Para" /><xsl:value-of select="//Text" /><xsl:value-of select="$Para" />Sincerely,<xsl:value-of select="$Para" /><xsl:value-of select="concat(//Sender/FirstName, ' ', //Sender/LastName)" /><xsl:value-of select="$NL" /><xsl:value-of select="//Sender/Title" /></xsl:template></xsl:stylesheet>

上面的样式表举例说明了concat和starts-with XPath串函数和怎样在输出文本中增加新行，还有定义和使用变量。
下面是程序的执行结果。

1.VC6建立Win32控制台应用程序。
2.在stdafx.h中添加下面的代码：

#include <TCHAR.H>#include <stdio.h>#include <time.h>#import "msxml4.dll"// If this import statement fails, you need to install MSXML 4.0 SP1 from://http://msdn.microsoft.com/downloads/sample.asp?url=/MSDN-FILES/027/001/766/msdncompositedoc.xml#include <msxml2.h>// If this include statement fails, you need to install MSXML 4.0 SP1 SDK from://http://msdn.microsoft.com/downloads/sample.asp?url=/MSDN-FILES/027/001/766/msdncompositedoc.xml// You also need to add the include file and library search path// to Visual C++'s list of directories (Tools > Options... > Directories).using namespace MSXML2;inline void EVAL_HR( HRESULT _hr )    { if FAILED(_hr) throw(_hr); }#define TEMP_SIZE  _MAX_PATH               // size of short bufferstatic _TCHAR   szTemp[TEMP_SIZE];         // multipurpose buffer on stackstatic DWord    dwLen;

3.上面的代码引入MSXML4类型库，包含MSXML头文件，检查HRESULT值并声明了一些全局变量。
4.main函数：

  int main(int argc, char* argv[]){ try {  EVAL_HR(CoInitialize(NULL));  // Make sure that MSXML 4.0 is installed  if (!isMSXMLInstalled())   return -1;  // Make sure that XML and XSL file names are passed  // as command line parameters  if (argc < 3)   // Show proper message here   return -1;    IXMLDOMDocument2Ptr pXMLDoc = NULL;  IXMLDOMDocument2Ptr pXSLDoc = NULL;    // Load the XML document  if (loadDocument(pXMLDoc, argv[1], true))  {   // Load the stylesheet   if (loadDocument(pXSLDoc, argv[2], false))   {    _ftprintf(stdout, pXMLDoc->transformNode(pXSLDoc));   }   else   {    printMSXMLError(pXSLDoc);   }  }  else  {   printMSXMLError(pXMLDoc);  } } catch(...) {//exception handling }  _ftprintf(stdout, "\n\nPress Enter to continue..."); getchar(); CoUninitialize(); return 0;}

5.XML文件和XSLT样式表文件名作为命令行参数传递给应用程序。主函数通过调用isMSXMLInstalled验证 MSXML4.0是否安装。接下来两次调用loadDocument;先是加载XML文档,然后是加载XSLT样式表。最后调用transformNode进行转换。

6.本例代码下载：http://www.perfectxml.com/CPPMSXML/downloads/20020716MailMerge.zip

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