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>

<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="'
'" />
<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 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, "\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。

标签: xpath串函数

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实例简析XPath串函数和XSLT

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