Extract value of attribute node via XPath

问题:

How can I extract the value of an attribute node via XPath?

A sample XML file is:

<parents name='Parents'>
  <Parent id='1' name='Parent_1'>
    <Children name='Children'>
      <child name='Child_2' id='2'>child2_Parent_1</child>
      <child name='Child_4' id='4'>child4_Parent_1</child>
      <child name='Child_1' id='3'>child1_Parent_1</child>
      <child name='Child_3' id='1'>child3_Parent_1</child>
    </Children>
  </Parent>
  <Parent id='2' name='Parent_2'>
    <Children name='Children'>
      <child name='Child_1' id='8'>child1_parent2</child>
      <child name='Child_2' id='7'>child2_parent2</child>
      <child name='Child_4' id='6'>child4_parent2</child>
      <child name='Child_3' id='5'>child3_parent2</child>
    </Children>
  </Parent>
</parents>

So far I have this XPath string:

//Parent[@id='1']/Children/child[@name]  

It returns only child elements, but I would like to have the value of the name attribute.

For my sample XML file, here's what I'd like the output to be:

Child_2
Child_4
Child_1
Child_3

回答1:

//Parent[@id='1']/Children/child/@name 

Your original child[@name] means an element child which has an attribute name. You want child/@name.

回答2:

To get just the value (without attribute names), use string():

string(//Parent[@id='1']/Children/child/@name)

The fn:string() fucntion will return the value of its argument as xs:string. In case its argument is an attribute, it will therefore return the attribute's value as xs:string.

回答3:

You should use //Parent[@id='1']/Children/child/data(@name)

The attributes can not be serialized so you can't return them in an xml looking result. What you need to do is obtain the data from the attribute using data() function.

回答4:

As answered above:

//Parent[@id='1']/Children/child/@name 

will only output the name attribute of the 4 child nodes belonging to the Parent specified by its predicate [@id=1]. You'll then need to change the predicate to [@id=2] to get the set of child nodes for the next Parent.

However, if you ignore the Parent node altogether and use:

//child/@name

you can select name attribute of all child nodes in one go.

name="Child_2"
name="Child_4"
name="Child_1"
name="Child_3"
name="Child_1"
name="Child_2"
name="Child_4"
name="Child_3"

回答5:

//Parent/Children[@  Attribute='value']/@Attribute

This is the case which can be used where element is having 2 attribute and we can get the one attribute with the help of another one.

回答6:

@ryenus, You need to loop through the result. This is how I'd do it in vbscript;

Set xmlDoc = CreateObject("Msxml2.DOMDocument")
xmlDoc.setProperty "SelectionLanguage", "XPath"
xmlDoc.load("kids.xml")

'Remove the id=1 attribute on Parent to return all child names for all Parent nodes
For Each c In xmlDoc.selectNodes ("//Parent[@id='1']/Children/child/@name")
    Wscript.Echo c.text
Next

回答7:

for all xml with namespace use local-name()

//*[local-name()='Parent'][@id='1']/*[local-name()='Children']/*[local-name()='child']/@name