使用 local-name() 获取 XSLT 中的第一个子节点 [英] Get first child node in XSLT using local-name()

问题描述

假设我们有这个简单的 xml ...

Assume we have this simple xml ...

 <books>   
    <book>
       <author/>
       <title/>
    </book>
    <book>
       <author/>
       <title/>
    </book>
 </books>

我使用这个 xpath 来获取第一个 book 实例的元素.

I'm using this xpath to get the elements of the first book instance.

//books[1]/*

退货

<author/>
<title/>

这很好用，但我必须使用 local-name() 让它工作.我尝试了以下但这些都不起作用...

And that works fine, but I have to get it working using local-name(). I've tried the following but none of these work...

//*[local-name()='books']/*

这会返回重复的作者和标题元素，不好，我只需要第一个孩子的它们

this returns repeating author and title elements, not good, I only need them from the first child

//*[local-name()='books'][0]/*

这不会返回任何东西

基本上，我想创建一个 CSV 文件，因此输出中的第一行将是一个标题，列出书籍属性名称，后跟任意数据值.我只需要让标题部分工作.

Basically, I want to create a CSV file, so the first line in the output will be a header listing the book attribute names followed by the arbitrary data values. I only need to get the header part working.

author,title
john,The End is Near
sally,Looking for Answers

推荐答案

你说的路径表达式适合你

The path expression you say works for you

//books[1]/*

生成第一次(并且仅在这种情况下)出现的任何 <books> 的所有子节点的列表.节点.因为，在您的数据中，唯一出现的 <books>是根，同

generates a list of all child nodes of the first (and only in this case) occurrence of any <books> node. Because, in your data, the only occurrence of <books> is at the root, it is the same as

/books/*

返回两个 <book>节点，所以你说它只返回一个节点是错误的.

which returns two <book> nodes, and so you are wrong to say that it returns only one node.

很难知道您需要什么，就好像您总是将 local-name 应用于根节点，那么您就不需要知道它的名称，只需使用 即可访问它/*，所以你只需要

It is hard to know what you need, as if you are always applying local-name to the root node then you do not need to know its name and can access it with just /*, so you would want simply

/*/*[1]

但是要访问 的第一个子节点节点在您要编写的文档中的任何位置

However to access the first child node of a <books> node anywhere in the document you would write

//*[local-name()='books']/*[1]

您应该尽可能地限制上下文，因为以 // 开头的 XPath 表达式将强制搜索整个文档，如果节点问题总是在根源上.

You should be careful to confine your context as much as possible, as starting the XPath expression with // will force a search of the entire document, which is pointless and time-consuming if the node in question is always at the root.

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