XPath表达式不为//元素返回任何内容，但是//*返回一个计数 [英] XPath Expression returns nothing for //element, but //* returns a count
问题描述
我正在将XOM与以下示例数据一起使用:
I'm using XOM with the following sample data:
Element root = cleanDoc.getRootElement();
//find all the bold elements, as those mark institution and clinic.
Nodes nodes = root.query("//*");
<html xmlns="http://www.w3.org/1999/xhtml" xmlns:html="http://www.w3.org/1999/xhtml">
<head>
<title>Patient Information</title>
</head>
</html>
以下元素返回许多元素(来自真实数据):
The following element returns many elements (from real data):
//*
但类似
//head
不返回任何内容.如果我遍历根的子级，则数字似乎匹配，并且如果打印元素名称，则一切看起来都正确.
Returns nothing. If I run through the children of the root, the numbers seem to match up, and if I print the element name, everything seems to look correct.
我正在获取HTML，并使用tagsoup对其进行解析，然后从结果字符串构建XOM文档.哪一部分会如此严重地出错?我觉得这里发生了一些奇怪的编码问题，但我只是没有看到它. Java字符串是字符串，对吧?
I'm taking HTML, parsing it with tagsoup, and then building a XOM Document from the resulting string. What part of this could go so horribly wrong? I feel there's some weird encoding issue going on here, but I'm just not seeing it. Java Strings are Strings, right?
推荐答案
您的文档具有默认名称空间，这意味着在XPath模型中所有元素都位于该名称空间中.
Your document has a default namespace, which means in the XPath model all the elements are in that namespace.
查询应为//html:head.您将必须提供名称空间映射到XPath查询.
The query should be //html:head. You will have to supply the namespace mapping to the XPath query.
请注意，尽管XPath表达式使用名称空间前缀，但必须匹配的是名称空间uri.
Note that while the XPath expression uses a namespace prefix, it is the namespace uri that must match.
XPathContext ctx = new XPathContext("html", "http://www.w3.org/1999/xhtml");
Nodes nodes = root.query("//html:head", ctx );
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