XPATH is XML path language. As from abbreviation, it is an XML language which is use for the query to selecting XML node from XML document.
XPath also used for compute values (e.g., strings, numbers, or Boolean values) and converting values from one type to other from the content of XML documents.
XPath was defined by World Wide Web Consortium (W3C).
This is Complete Tutorial in which I will explain everything Which is closely related to XPATH.
XPath is used to navigate through elements and attributes in an XML document.
XPath Path Expressions
XPath uses path expressions to select nodes or node-sets in an XML document. These path expressions look very much like the expressions you see when you work with a traditional computer file system.
XPath Standard Functions
XPath includes over 100 built-in functions. There are functions for string values, numeric values, date and time comparison, type conversion, node and QName manipulation, sequence manipulation, Boolean values, and etc.
XPath Terminology
Nodes
In XPath, there are seven kinds of nodes: element, attribute, text, namespace, processing-instruction, comment, and document nodes
XML documents are treated as trees of nodes. The topmost element of the tree is called the root element.
look following sample XML document:
Explanation of nodes in the above XML document :<?xml version="1.0" encoding="ISO-8859-1"?> <bookstore> <book> <title lang="en">Harry Potter</title> <author>J K. Rowling</author> <year>2005</year> <price>29.99</price> </book> </bookstore>
Atomic values<bookstore> (root element node) <author>J K. Rowling</author> (element node) lang="en" (attribute node)
Atomic values are nodes with no children or parent.
Example of atomic values:
J K. Rowling
"en"
Items
Items are atomic values or nodes.
Relationship of Nodes
Parent
Each element and attribute has one parent.
In the above example; the book element is the parent of the title, author, year, and price:
Each element and attribute has one parent.
In the above example; the book element is the parent of the title, author, year, and price:
Children
Element nodes may have zero, one or more children.
In the above example; the title, author, year, and price elements are all children of the book element:
Element nodes may have zero, one or more children.
In the above example; the title, author, year, and price elements are all children of the book element:
Siblings
Nodes that have the same parent.
In the above example; the title, author, year, and price elements are all siblings:
Nodes that have the same parent.
In the above example; the title, author, year, and price elements are all siblings:
Ancestors
A node's parent, parent's parent, etc.
In the above example; the ancestors of the title element are the book element and the bookstore element:
A node's parent, parent's parent, etc.
In the above example; the ancestors of the title element are the book element and the bookstore element:
Descendants
A node's children, children's children, etc.
In the above example; descendants of the bookstore element are the book, title, author, year, and price elements:
A node's children, children's children, etc.
In the above example; descendants of the bookstore element are the book, title, author, year, and price elements:
XPath Syntax
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:
node name:-
Selects all nodes with the name "node name"
/:-
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
Here we have listed some path expressions and the result of the expressions:
bookstore:-
Selects all nodes with the name "bookstore"
/bookstore:-
Select 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.
we have listed some path expressions with predicates and the result of the expressions:
/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.
* :-
Matches any element node
@*:-
Matches any attribute node
node() :-
Matches any node of any kind
Examples:-
/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.
we have listed some path expressions and the result of the expressions:
//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
XPath Operators
An XPath expression returns either a node-set, a string, a Boolean, or a number.
Below is a list of the operators that can be used in XPath expressions:
| Computes two node-sets,
+ Addition,
- Subtraction,
* Multiplication,
div Division,
= Equal,
!= Not equal,
< Less than,
<= Less than or equal to,9.00
> Greater than,
>= Greater than or equal to,price is 9.90
or or,
and and,
mod Modulus (division remainder).
The XML Example Document
We will use the following XML document in the examples below.Create an XML File save as "books.xml" with following data:-<?xml version="1.0" encoding="ISO-8859-1"?> <bookstore> <book category="COOKING"> <title lang="en">Everyday Italian</title> <author>Giada De Laurentiis</author> <year>2005</year> <price>30.00</price> </book> <book category="CHILDREN"> <title lang="en">Harry Potter</title> <author>J K. Rowling</author> <year>2005</year> <price>29.99</price> </book> <book category="WEB"> <title lang="en">XQuery Kick Start</title> <author>James McGovern</author> <author>Per Bothner</author> <author>Kurt Cagle</author> <author>James Linn</author> <author>Vaidyanathan Nagarajan</author> <year>2003</year> <price>49.99</price> </book> <book category="WEB"> <title lang="en">Learning XML</title> <author>Erik T. Ray</author> <year>2003</year> <price>39.95</price> </book> </bookstore>
Select all the titles
Now we select all titles from XML document:-<!DOCTYPE html> <html> <body> <script> function loadXMLDoc(dname) { if (window.XMLHttpRequest) { xhttp=new XMLHttpRequest(); } else { xhttp=new ActiveXObject("Microsoft.XMLHTTP"); } xhttp.open("GET",dname,false); xhttp.send(""); return xhttp.responseXML; } xml=loadXMLDoc("books.xml"); path="/bookstore/book/title" // code for IE if (window.ActiveXObject) { var nodes=xml.selectNodes(path); for (i=0;i<nodes.length;i++) { document.write(nodes[i].childNodes[0].nodeValue); document.write("<br>"); } } // code for Mozilla, Firefox, Opera, etc. else if (document.implementation && document.implementation.createDocument) { var nodes=xml.evaluate(path, xml, null, XPathResult.ANY_TYPE, null); var result=nodes.iterateNext(); while (result) { document.write(result.childNodes[0].nodeValue); document.write("<br>"); result=nodes.iterateNext(); } } </script> </body> </html> Output:- Everyday Italian Harry Potter XQuery Kick Start Learning XML
Select the title of the first book
just replace path variable (in above code) value with
/bookstore/book[1]/title
Select price nodes with price>35
just replace path variable (in above code) value with
/bookstore/book[price>35]/price
For Xpath Function please follow the below Link :
XPath basic Function
0 comments:
Post a Comment