XPath

Selecting Nodes

XPath uses path expressions to select nodes in an XML document. The most useful path expressions are listed below:

ExpressionDescription
nodenameSelects all nodes with the name "nodename"
/Selects from the root node
//Selects nodes in the document from the current node that match the selection no matter where they are
.Selects the current node
..Selects the parent of the current node
@Selects attributes

We will be presenting a couple of XPath examples for the following example of XML document :

<bookstore>
  <book>
    <title lang="en">A Clockwork Orange</title>
    <author>Anthony Burgess</author>
    <year>1962</year>
    <price>19.99</price>
  </book>
  <book>
    <title lang="en">Nineteen Eighty-Four</title>
    <author>George Orwell</author>
    <year>1949</year>
    <price>14.99</price>
  </book>
</bookstore>


Here are some path expressions and the result of the expressions:

Path ExpressionResult
bookstoreSelects all nodes with the name "bookstore"
/bookstoreSelects the root element bookstore

Note: If the path starts with a slash ( / ) it always represents an absolute path to an element!

bookstore/bookSelects all book elements that are children of bookstore
//bookSelects all book elements no matter where they are in the document
bookstore//bookSelects all book elements that are descendant of the bookstore element, no matter where they are under the bookstore element
//@langSelects all attributes that are named lang

Predicates

Predicates are used to find a specific node or a node that contains a specific value. Predicates are always embedded in square brackets.

In the table below we have listed some path expressions with predicates and the result of the expressions:

Path ExpressionResult
/bookstore/book[1]Selects the first book element that is the child of the bookstore element.

Note: In IE 5,6,7,8,9 first node is[0], but according to W3C, it is [1]. To solve this problem in IE, set the SelectionLanguage to XPath:

In JavaScript: xml.setProperty("SelectionLanguage","XPath");
/bookstore/book[last()]Selects the last book element that is the child of the bookstore element
/bookstore/book[last()-1]Selects the last but one book element that is the child of the bookstore element
/bookstore/book[position()<3]Selects the first two book elements that are children of the bookstore element
//title[@lang]Selects all the title elements that have an attribute named lang
//title[@lang='en']Selects all the title elements that have a "lang" attribute with a value of "en"
/bookstore/book[price>35.00]Selects all the book elements of the bookstore element that have a price element with a value greater than 35.00
/bookstore/book[price>35.00]/titleSelects all the title elements of the book elements of the bookstore element that have a price element with a value greater than 35.00

Selecting Unknown Nodes

XPath wildcards can be used to select unknown XML nodes.

WildcardDescription
*Matches any element node
@*Matches any attribute node
node()Matches any node of any kind


In the table below we have listed some path expressions and the result of the expressions:

Path ExpressionResult
/bookstore/*Selects all the child element nodes of the bookstore element
//*Selects all elements in the document
//title[@*]Selects all title elements which have at least one attribute of any kind

Selecting Several Paths

By using the | operator in an XPath expression you can select several paths.

In the table below we have listed some path expressions and the result of the expressions:

Path ExpressionResult
//book/title | //book/priceSelects all the title AND price elements of all book elements
//title | //priceSelects all the title AND price elements in the document
/bookstore/book/title | //priceSelects all the title elements of the book element of the bookstore element AND all the price elements in the document

XPath Axes

An axis defines a node-set relative to the current node.

AxisNameResult
ancestorSelects all ancestors (parent, grandparent, etc.) of the current node
ancestor-or-selfSelects all ancestors (parent, grandparent, etc.) of the current node and the current node itself
attributeSelects all attributes of the current node
childSelects all children of the current node
descendantSelects all descendants (children, grandchildren, etc.) of the current node
descendant-or-selfSelects all descendants (children, grandchildren, etc.) of the current node and the current node itself
followingSelects everything in the document after the closing tag of the current node
following-siblingSelects all siblings after the current node
namespaceSelects all namespace nodes of the current node
parentSelects the parent of the current node
precedingSelects all nodes that appear before the current node in the document, except ancestors, attribute nodes and namespace nodes
preceding-siblingSelects all siblings before the current node
selfSelects the current node

XPath Operators

Below is a list of the operators that can be used in XPath expressions:

OperatorDescriptionExample
|Computes two node-sets//book | //cd
+Addition6 + 4
-Subtraction6 - 4
*Multiplication6 * 4
divDivision8 div 4
=Equalprice=9.80
!=Not equalprice!=9.80
<Less thanprice<9.80
<=Less than or equal toprice<=9.80
>Greater thanprice>9.80
>=Greater than or equal toprice>=9.80
ororprice=9.80 or price=9.70
andandprice>9.00 and price<9.90
modModulus (division remainder)5 mod 2

Copyright © 2010 - 2023 Emakin. All rights reserved.