Extract value of attribute node via XPath – Dev

The best answers to the question “Extract value of attribute node via XPath” in the category Dev.

QUESTION:

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

ANSWER:

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.

ANSWER:

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

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

ANSWER:

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"

ANSWER:

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.