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XPath Syntax

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XPath uses path expressions to select nodes or node-sets in an XML document.The node is selected by following a path or steps.

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The XML Example Document

We will use the following XML document in the examples below.

 
  29.99



 
  39.95

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Selecting Nodes

XPath uses path expressions to select nodes in an XML document. The node is selected by following a path or steps.The most usefulpath expressions are listed below:

Expression Description nodename Selects all child nodes of the named node / 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

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

Path Expression Result bookstore Selects all the child nodes of the bookstore element /bookstore Selects the root element bookstore

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

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

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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 theexpressions:

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

Note: IE5 and later has implemented that [0] should be the first node, but according to the W3C standard it should have been [1]!!

/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='eng'] Selects all the title elements that have an attribute named lang with a value of 'eng' /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]/title Selects all the title elements of the book elements of the bookstore element that have a price element with a value greater than 35.00

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Selecting Unknown Nodes

XPath wildcards can be used to select unknown XML elements.

Wildcard Description * 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 theexpressions:

Path Expression Result /bookstore/* Selects all the child nodes of the bookstore element //* Selects all elements in the document //title[@*] Selects all title elements which have any attribute

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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 theexpressions:

Path Expression Result //book/title | //book/price Selects all the title AND price elements of all book elements //title | //price Selects all the title AND price elements in the document /bookstore/book/title | //price Selects all the title elements of the book element of the bookstore element AND all the price elements in the document