Saturday, July 10, 2010

XPath

All text is from www.w3schools.com/XPath/


XPath is a language for finding information in an XML document.
XPath includes over 100 built-in functions. There are functions for string values, numeric values, date and time comparison, node and QName manipulation, sequence manipulation, Boolean values, and more.
In XPath, there are seven kinds of nodes:
  1. element
  2. attribute
  3. text
  4. namespace
  5. processing-instruction
  6. comment
  7. document nodes



The XML Example Document


 

Selecting Nodes

Path ExpressionResult
bookstoreSelects all the child nodes of the bookstore element
/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 always embedded in square brackets.
Path ExpressionResult
/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]/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

Wildcard

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 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.
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

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 everything in the document that is before the start tag of the current node
preceding-siblingSelects all siblings before the current node
selfSelects the current node

The syntax for a location step is:

axisname::nodetest[predicate]

Examples

ExampleResult
child::bookSelects all book nodes that are children of the current node
attribute::langSelects the lang attribute of the current node
child::*Selects all children of the current node
attribute::*Selects all attributes of the current node
child::text()Selects all text child nodes of the current node
child::node()Selects all child nodes of the current node
descendant::bookSelects all book descendants of the current node
ancestor::bookSelects all book ancestors of the current node
ancestor-or-self::bookSelects all book ancestors of the current node - and the current as well if it is a book node
child::*/child::priceSelects all price grandchildren of the curren




Examples

Select all the titles
/bookstore/book/title
Select the title of the first book
/bookstore/book[1]/title
Select price nodes with price>35
/bookstore/book[price>35]/price
Select title nodes with price>35
/bookstore/book[price>35]/title

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