XPath Syntax
XPath uses path expressions to select nodes or node-sets in an XML document.
The node is selected by following a path or steps.
The XML Example Document
We will use the following XML document in the examples below.
<?xml version="1.0" encoding="ISO-8859-1"?>
<bookstore>
<book>
<title lang="eng">Harry Potter</title>
<price>29.99</price>
</book>
<book>
<title lang="eng">Learning XML</title>
<price>39.95</price>
</book>
</bookstore>
|
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 useful
path 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 |
Examples
In the table below we have listed some path expressions and the result of the
expressions:
| 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 |
Predicates
Predicates are used to find a specific node or a node that contains a specific value.
Predicates are always embedded in square brackets.
Examples
In the table below we have listed some path expressions with predicates and the result of the
expressions:
| 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 |
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 |
Examples
In the table below we have listed some path expressions and the result of the
expressions:
| 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 |
Selecting Several Paths
By using the | operator in an XPath expression you can select several paths.
Examples
In the table below we have listed some path expressions and the result of the
expressions:
| 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 |
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