xpath parent attribute of selection

问题

Syntax of the xml document:

<x name="GET-THIS">
  <y>
    <z>Z</z> 
    <z>Z__2</z>
    <z>Z__3</z>   
  </y>
</x>

I'm able to get all z elements using:

xpath("//z")

But after that I got stuck, I'm not sure what to do next. I don't really understand the syntax of the .. parent method

So, how do I get the attribute of the parent of the parent of the element?

回答1:

Instead of traversing back to the parent, just find the right parent to begin with:

• //x will select all x elements.
• //x[//z] will select all x elements which have z elements as descendants.
• //x[//z]/@name will get the name attribute of each of those elements.

回答2:

You already have a good accepted answer, but here are some other helpful expressions:

• //z/ancestor::x/@name - Find <z> elements anywhere, then find all the ancestor <x> elements, and then the name="…" attributes of them.

• //z/../../@name - Find the <z> elements, and then find the parent node(s) of those, and then the parent node(s) of those, and then the name attribute(s) of the final set.

  • This is the same as: //z/parent::*/parent::*/@name, where the * means "an element with any name".

• The // is useful, but inefficient. If you know that the hierarchy is x/y/z, then it is more efficient to do something like //x[y/z]/@name

回答3:

I dont have a reputation, so I cannot add comment to accepted answer by Blender. But his answer will not work in general. Correct version is

//x[.//z]/@name

Explanation is simple - when you use filter like [//z] it will search for 'z' in global context, i.e. it returns true if xml contains at least one node z anywhere in xml. For example, it will select both names from xml below:

<root>
  <x name="NOT-THIS">
  </x>
  <x name="GET-THIS">
     <y>
        <z>Z</z> 
        <z>Z__2</z>
        <z>Z__3</z>   
     </y>
  </x>
</root>

Filter [.//z] use context of current node (.) which is xand return only 2nd name.

来源：https://stackoverflow.com/questions/16950608/xpath-parent-attribute-of-selection