如何在 Nokogiri 中将 xmlns 声明与 XPath 一起使用

问题描述

我正在使用 Nokogiri::XML 来解析来自 Amazon SimpleDB 的响应.响应类似于:

I'm using Nokogiri::XML to parse responses from Amazon SimpleDB. The response is something like:

<SelectResponse xmlns="http://sdb.amazonaws.com/doc/2007-11-07/">
  <SelectResult>
    <Item>
      <Attribute><Name>Foo</Name><Value>42</Value></Attribute>
      <Attribute><Name>Bar</Name><Value>XYZ</Value></Attribute>
    </Item>
  </SelectResult>
</SelectResponse>

如果我直接将响应交给 Nokogiri，所有 XPath 查询(例如 doc/"//Item/Attribute[Name='Foo']/Value")都会返回一个空数组.但是，如果我从 SelectResponse 标记中删除 xmlns 属性，它就可以完美运行.

If I just hand the response straight over to Nokogiri, all XPath queries (e.g. doc/"//Item/Attribute[Name='Foo']/Value") return an empty array. But if I remove the xmlns attribute from the SelectResponse tag, it works perfectly.

我需要做一些额外的事情来说明命名空间声明吗?这种变通方法感觉非常像黑客.

Is there some extra thing I need to do to account for the namespace declaration? This workaround feels horribly like a hack.

推荐答案

该 XPath 查询查找不在任何命名空间中的元素.您需要告诉您的 XPath 处理器您正在 http://sdb.amazonaws.com/doc/2007-11-07/ 命名空间中查找元素.

That XPath query looks for elements that are not in any namespace. You need to tell your XPath processor that you are looking for elements in the http://sdb.amazonaws.com/doc/2007-11-07/ namespace.

使用 Nokogiri 做到这一点的一种方法是:

One way to do that with Nokogiri is:

doc = Nokogiri::XML.parse(...)
doc.xpath("//aws:Item/aws:Attribute[Name='Foo']/aws:Value", {"aws" => "http://sdb.amazonaws.com/doc/2007-11-07/"})

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