查找XML文档中的所有名称空间声明 - xPath 1.0 vs xPath 2.0 [英] Find all namespace declarations in an XML document - xPath 1.0 vs xPath 2.0

问题描述

作为Java 6应用程序的一部分，我想在XML文档中找到所有名称空间声明，包括任何重复项。

As part of a Java 6 application, I want to find all namespace declarations in an XML document, including any duplicates.

编辑 ：Per Martin的请求，这是我正在使用的Java代码：

Edit: Per Martin's request, here's the Java code I am using:

XPathFactory xPathFactory = XPathFactory.newInstance();
XPath xPath = xPathFactory.newXPath();
XPathExpression xPathExpression = xPathExpression = xPath.compile("//namespace::*"); 
NodeList nodeList = (NodeList) xPathExpression.evaluate(xmlDomDocument, XPathConstants.NODESET);

假设我有这个XML文档：

Suppose I have this XML document:

<?xml version="1.0" encoding="UTF-8"?>
<root xmlns:ele="element.com" xmlns:att="attribute.com" xmlns:txt="textnode.com">
    <ele:one>a</ele:one>
    <two att:c="d">e</two>
    <three>txt:f</three>
</root>

要查找所有名称空间声明，我将此xPath语句应用于XML文档使用xPath 1.0 ：

To find all namespace declarations, I applied this xPath statement to the XML document using xPath 1.0:

//namespace::*

它找到4个命名空间声明，这是我期望的（和期望）：

It finds 4 namespace declarations, which is what I expect (and desire):

/root[1]/@xmlns:att - attribute.com
/root[1]/@xmlns:ele - element.com
/root[1]/@xmlns:txt - textnode.com
/root[1]/@xmlns:xml - http://www.w3.org/XML/1998/namespace

但如果我改用使用xPath 2.0 ，那么我得到16个命名空间声明（每个先前的声明4次），这不是我的意思期待（或渴望）：

But if I change to using xPath 2.0, then I get 16 namespace declarations (each of the previous declarations 4 times), which is not what I expect (or desire):

/root[1]/@xmlns:xml - http://www.w3.org/XML/1998/namespace
/root[1]/@xmlns:att - attribute.com
/root[1]/@xmlns:ele - element.com
/root[1]/@xmlns:txt - textnode.com
/root[1]/@xmlns:xml - http://www.w3.org/XML/1998/namespace
/root[1]/@xmlns:att - attribute.com
/root[1]/@xmlns:ele - element.com
/root[1]/@xmlns:txt - textnode.com
/root[1]/@xmlns:xml - http://www.w3.org/XML/1998/namespace
/root[1]/@xmlns:att - attribute.com
/root[1]/@xmlns:ele - element.com
/root[1]/@xmlns:txt - textnode.com
/root[1]/@xmlns:xml - http://www.w3.org/XML/1998/namespace
/root[1]/@xmlns:att - attribute.com
/root[1]/@xmlns:ele - element.com
/root[1]/@xmlns:txt - textnode.com

即使是我使用xPath语句的非缩写版本：

This same difference is seen even when I use the non-abbreviated version of the xPath statement:

/descendant-or-self::node()/namespace::*

它可以在各种XML解析器中看到（LIBXML，MSXML.NET，Saxon）在oXygen测试。 （编辑：正如我在评论中稍后提到的，这种说法不正确。虽然我认为我正在测试各种XML解析器，但我真的不是。）

And it is seen across a variety of XML parsers (LIBXML, MSXML.NET, Saxon) as tested in oXygen. ( As I mention later in the comments, this statement is not true. Though I thought I was testing a variety of XML parsers, I really wasn't.)

问题＃1：为什么从xPath 1.0到xPath 2.0的区别？

Question #1: Why the difference from xPath 1.0 to xPath 2.0?

问题＃2 ：使用xPath 2.0获得所需结果是否可能/合理？

Question #2: Is it possible/reasonable to get desired results using xPath 2.0?

提示：使用 distinct-values（） xPath 2.0中的函数将不返回所需的结果，因为我想要所有名称空间声明，即使同一名称空间被声明两次。例如，请考虑以下XML文档：

Hint: Using the distinct-values() function in xPath 2.0 will not return the desired results, as I want all namespace declarations, even if the same namespace is declared twice. For example, consider this XML document:

<?xml version="1.0" encoding="UTF-8"?>
<root>
    <bar:one xmlns:bar="http://www.bar.com">alpha</bar:one>
    <bar:two xmlns:bar="http://www.bar.com">bravo</bar:two>
</root>

所需的结果是：

/root[1]/@xmlns:xml - http://www.w3.org/XML/1998/namespace
/root[1]/bar:one[1]/@xmlns:bar - http://www.bar.com
/root[1]/bar:two[1]/@xmlns:bar - http://www.bar.com

推荐答案

我认为这将获得所有名称空间，没有任何重复：

I think this will get all namespaces, without any duplicates:

for $i in 1 to count(//namespace::*) return 
if (empty(index-of((//namespace::*)[position() = (1 to ($i - 1))][name() = name((//namespace::*)[$i])], (//namespace::*)[$i]))) 
then (//namespace::*)[$i] 
else ()

这篇关于查找XML文档中的所有名称空间声明 - xPath 1.0 vs xPath 2.0的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！