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
DateJuly 17, 2002/Date
To
FirstNameVicky/FirstName
LastNameP/LastName
SexMale/Sex
/To
Address
Line1900 National Pkwy/Line1
Line2Suite 105/Line2
CityBellevue/City
StateWA/State
Zip98007/Zip
CountryUSA/Country
/Address
SubjectESTATE OF JOHN DOE / FILE NO. 12345.6789/Subject
Text
Please pay the property taxes as soon as possible.
/Text
Sender
FirstNameJohn/FirstName
LastNameM/LastName
TitleSr. 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="'
'" /
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:ifxsl: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 buffer
static _TCHAR szTemp[TEMP_SIZE]; // multipurpose buffer on stack
static 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, "Press 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
译自PerfectXML
