使用 XSLT 预处理 XML 中的 #ifdefs [英] Using XSLT to preprocess #ifdefs in XML

问题描述

这大概是使用 XSLT 作为 XML 预处理器的几乎副本处理器 但是由于该问题的 OP 没有发布完整的示例，尽管被要求，但对于不熟悉 XSLT 的任何人来说，这些回复都没有用.广泛的网络搜索也没有发现任何有用的东西 - XSLT 似乎非常缺乏文档，并且在网络上很少讨论.

This is presumably an almost carbon copy of Using XSLT as an XML pre-processor But as the OP of that question did not post a full example, despite being asked to, the replies are no use to anyone not familiar with XSLT. Neither have extensive web searches turned up anything helpful - XSLT seems remarkably poorly documented and little discussed on the Web.

无论如何...

我有一个 XML 文件，比如说 foo.xml，如下(显然已经大大简化了):

I have an XML file, say foo.xml, as follows (greatly simplified, obviously):

 <?xml version="1.0" encoding="UTF-8"?>

 <main>

  <fee>blah</fee>

  <ifdef select="OLD_VERSION">
   <fi>blah blah</fi>
  </ifdef>

  </main>

(根据 Ian Roberts 的回答，C 风格的 #ifdef 更改为ifdef"块)

(C-style #ifdef changed to "ifdef" block in light of Ian Roberts's answer)

我想在linux上运行一个xsltproc命令，如下:

I want to run an xsltproc command on linux, as follows:

xsltproc --stringparam xmlver NEW_VERSION --nonet foo.xslt foo.xml

并使用以下 XSLT 文件 foo.xslt 来排除 #ifdef'ed 部分:

and have this use the following XSLT file, foo.xslt, to exclude the #ifdef'ed section:

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

 <xsl:output method="xml" />
 <xsl:param name="xmlver" required="yes"/>

 <xsl:template match="node() | @*">
  <xsl:copy><xsl:apply-templates select="node() | @*"/></xsl:copy>
 </xsl:template>

 <xsl:variable name="defines" select="document($xmlver)/defines"/>

 <xsl:template match="ifdef">

  <xsl:variable name="this" select="."/>

  <xsl:for-each select="$defines[def = $this/@select]">
   <xsl:apply-templates select="$this/node()" />
  </xsl:for-each>

 </xsl:template>

</xsl:stylesheet>

(我确实使用了对上面引用的问题的答复来构建此 XSLT；但是缺少的要素是在何处/如何合并xmlver"值.当然不能保证上面的内容是正确的；但是这个基本上我要问的是 - 如何以有效的方式将所有这些组合在一起?)

(I did use the replies to the question referenced above to construct this XSLT; but the missing ingredient is where/how to incorporate the "xmlver" value. Of course there is no guarantee it is correct in the above; but this essentially what I am asking - How is all this put together in a way that works?)

任何建设性的答复将不胜感激，并且无疑对将来有类似需求的许多人有用；但请不要厌烦，教条的你为什么要这样做?"回复！

Any constructive replies will be greatly appreciated, and will doubtless be useful to many people with a similar requirement in the future; but please no tiresome, dogmatic "Why would you want to do that?" replies!

推荐答案

您提到的问题看起来像是基于 XML 结构，该结构将 XML 元素用于其 ifdef.在您的情况下，您的 #ifdef 行不是 XML 元素，因此您无法将它们与 XSLT 模板匹配.如果您需要对其进行其他 XML 感知处理，最好使用非 XML 工具(甚至可能是普通的 C 预处理器)来处理 ifdef 并将生成的 XML 提供给 XSLT.

The question you refer to looks like it's based on an XML structure that uses XML elements for its ifdefs. In your case your #ifdef lines are not XML elements, so you can't match them with an XSLT template. You'd be better off using a non-XML tool (possibly even the normal C pre-processor) to handle the ifdefs and feed the resulting XML to an XSLT if you need to do other XML-aware processing on it.

如果您愿意为 ifdef 使用真正的 XML 元素，如上一个问题所示:

If you're happy to use real XML elements for your ifdefs, as in the previous question:

<?xml version="1.0" encoding="UTF-8"?>
<main>
  <fee>blah</fee>

  <ifdef select="OLD_VERSION">
   <fi>blah blah</fi>
  </ifdef>

</main>

那么问题就变成了如何将 xmlver 命令行参数视为您想要包含的单个 ifdef，而不是作为加载一整套定义的文件位置(这就是上一个问题的工作方式).这要简单得多:

then the question becomes how to treat the xmlver command line parameter as the single ifdef that you want to include, rather than as the location of a file from which to load a whole set of defines (which is how the previous question worked). That is much simpler:

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

 <xsl:output method="xml" />
 <xsl:param name="xmlver" />

 <xsl:template match="node() | @*">
  <xsl:copy><xsl:apply-templates select="node() | @*"/></xsl:copy>
 </xsl:template>

 <xsl:template match="ifdef">
 <!-- for the ifdef we want, include all its child elements, text nodes etc
      but not its attributes, for other ifdefs do nothing -->    
  <xsl:if test="@select = $xmlver">
   <xsl:apply-templates select="node()" />
  </xsl:if>
 </xsl:template>

</xsl:stylesheet>

我之前的尝试使用了 <xsl:template match="ifdef[@select=$xmlver]">，它适用于某些处理器，但不适用于 xsltproc(它是 技术上不允许 XSLT 规范，并且 xsltproc 比我通常的测试工具更严格，夏兰).

My previous attempt at this used a <xsl:template match="ifdef[@select=$xmlver]">, which works in some processors but not in xsltproc (it is technically not allowed by the XSLT spec, and xsltproc is stricter than my usual test harness, Xalan).

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