Finding the specified node through XPath

using XPath to find the need to introduce Jaxen-xx-xx.jar, otherwise it will report java.lang.noclassdeffounderror:org/jaxen/jaxenexception exception.

List list=document. selectnodes ("/books/book/@show");

XPath syntax 1, selecting nodes

XPath uses a path expression to select a node in an XML document, and the node is selected along a path or step.

Common Path Expressions:

An expression	Describe
NodeName	Selects all child nodes of the current node
/	Select from the root node
//	Selects nodes in the document from the current node of the matching selection, regardless of their location
.	Select the current node
..	Select the parent node of the current node
@	Select Properties

Instance

path expression   /p>	result
Bookstore	Select all child nodes of the bookstore element
/bookstore	Select root element bookstore
Bookstore/book	The Selects all child elements named book under Bookstore .
//book	Select all book child elements, regardless of their position in the document.
Bookstore//book	Select All Bookstore under the name book descendant elements , regardless of where they are located under bookstore.
// @ lang	Select All properties named Lang.

2. Predicate (predicates)

To find a particular node or a node that contains a specified value.

The predicate is embedded in square brackets.

Instance

Some path expressions for common predicates:

Path expression	Results
/BOOKSTORE/BOOK[1]	Selects the first book element that belongs to a bookstore child element.
/bookstore/book[last ()]	Select the last book element that belongs to the bookstore child element.
/bookstore/book[last ()-1]	Select the second-to-last book element that belongs to the bookstore child element.
/bookstore/book[position () <3]	Select The first two book element that belongs to the child element of the bookstore element.
title[@lang]	Select all the title elements that have properties named Lang.
title[@lang = ' Eng ']	Select all title elements that require these elements to have the Lang attribute value of Eng.
/BOOKSTORE/BOOK[PRICE>35.00]	Select the book element for all bookstore elements, which requires that the value of the child element of the book element, the price element, be greater than 35.00.
/bookstore/book[price>35.00]/title	Selects the title element of the book element in all bookstore elements, requiring that the value of the child element of the book element price element be greater than 35.00

3. Select Unknown node

XPath wildcard characters can be used to select unknown XML elements.

Wildcard characters	Describe
*	Match any element node
@*	Match any attribute node
Node ()	Match any type of node

Instance

Path expression	Results
/bookstore/*	Selects all child nodes of the bookstore element
//*	Select all elements in a document
Title[@*]	Select all the title elements with attributes.

4. Select a number of paths

By using the '|' in a path expression operator, you can select a number of paths.

Instance

Path expression	Results
Book/title | //book/price	Selects the title and price elements of all book elements.
Title | //price	Select the title and price elements in all documents.
/bookstore/book/title| Price	Select all the title elements of the book element that belong to the bookstore element, and all the price elements in the document.

5. XPath Axis

An axis defines a node set that is relative to the current node.

Axis Name	Results
Ancestor	Selects all ancestors of the current node (parent, grandfather, etc.)
Ancestor-or-self	Selects all ancestors of the current node (parent, grandfather, etc.) and the current node itself
Attribute	Selects all properties of the current node
Child	Selects all child elements of the current node.
Descendant	Selects all descendant elements (child, grandchild, and so on) of the current node.
Descendant-or-self	Selects all descendant elements (child, grandchild, and so on) of the current node and the current node itself.
Following	Selects all nodes after the end tag of the current node in the document.
Namespace	Selects all namespace nodes of the current node
Parent	Selects the parent node of the current node.
Preceding	Selects all nodes before the start tag of the current node in the document.
Preceding-sibling	Selects all sibling nodes before the current node.
Self	Select the current node.

6. Path

• Position path expression

The location path can be absolute, or it can be relative.

The absolute path starts with a forward slash (/), and the relative path does not. In both cases, the location path consists of one or more steps, each of which is split by a slash:

• Absolute location Path:
• Relative position path:

/step/step/...

step/step/...

Each step is calculated based on the nodes in the current node set.

• Step includes:

Axis: Defines the tree relationship between the selected node and the current node

Node Test (node-test): Identify the nodes inside an axis

0 or more predicates (predicate): Refine the selected node set more deeply

syntax for step : axis Name:: node test [predicate]

Instance

Example	Results
Child::book	Select all book nodes that belong to the child elements of the current node
Attribute::lang	Select the Lang property of the current node
Child::*	Selects all child elements of the current node
Attribute::*	Selects all properties of the current node
Child::text ()	Selects all the text subnodes of the current node
Child::node ()	Selects all child nodes of the current node
Descendant::book	Selects all book descendants of the current node
Ancestor::book	Selects all the book ancestors of the current node
Ancestor-or-self::book	Selects all the book ancestors of the current node and the current node (false so that the node is the book node)
Child::*/child::p	Selects all the price sun for the current node.

7. XPath operator

Operator	Describe	Instance	return value
|	Compute two node sets	Book | Cd	Returns all node sets with the book and CK elements
+	Addition	6 + 4	10
-	Subtraction	6-4	2
*	Multiplication	6 * 4	24
Div	Division	8 Div 4	2
=	Equals	price=9.80	Returns true if Price is 9.80. If Price is 9.90, the Fasle is returned.
!=	Not equal to	price!=9.80	Returns true if Price is 9.90. If Price is 9.80, the Fasle is returned.
<	Less than	price<9.80	Returns true if Price is 9.00. If Price is 9.90, the Fasle is returned.
<=	Less than or equal to	price<=9.80	Returns true if Price is 9.00. If Price is 9.90, the Fasle is returned.
>	Greater than	price>9.80	Returns true if Price is 9.90. If Price is 9.80, the Fasle is returned.
>=	Greater than or equal to	price>=9.80	Returns true if Price is 9.90. If Price is 9.70, the Fasle is returned.
Or	Or	price=9.80 or price=9.70	Returns true if Price is 9.80. If Price is 9.50, the Fasle is returned.
and	And	price>9.00 and price<9.90	Returns true if Price is 9.80. If Price is 8.50, the Fasle is returned.
MoD	Calculate the remainder of a division	5 MoD 2	1

Finding the specified node through XPath