To find 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, select the node

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

Common Path Expressions:

An expression	Description
NodeName	Select all child nodes of the current node
/	Selecting from the root node
//	Select the 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	Results
Bookstore	Select all child nodes of the bookstore element
/bookstore	Select the root element bookstore
Bookstore/book	Select all child elements with the name book under Bookstore.
Book	Selects all book child elements, regardless of their position in the document.
Bookstore//book	Select all descendant elements under bookstore whose name is book, regardless of where they are located under bookstore.
@Lang	Select All properties named Lang.

2. Predicate (predicates)

predicate pragmatics 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]	Select the first book element that belongs to the bookstore child element.
/bookstore/book[last ()]	Select the last book element that belongs to the bookstore child element.
/bookstore/book[last ()-1]	Select the penultimate book element that belongs to the bookstore child element.
/bookstore/book[position () <3]	Select The book element for the first two child elements that belong to the bookstore element.
title[@lang]	Select the title element for all properties that have the name Lang.
title[@lang = ' Eng ']	Select all the title elements and require that these elements have the lang attribute with the value eng.
/BOOKSTORE/BOOK[PRICE>35.00]	Selecting the book element for all bookstore elements requires the value of the child element price element of the book element to be greater than 35.00.
/bookstore/book[price>35.00]/title	Selects the title element of the book element in all bookstore elements, requiring the value of the child element price element of the book element to be greater than 35.00

3. Select Unknown node

XPath wildcard characters can be used to select an unknown XML element.

wildcard characters	Description
*	Match any element node
@*	Match any attribute node
Node ()	Match any type of node

Instance

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

4. Select several paths

By using the "|" in a path expression operator, you can select several paths.

Instance

Path Expression	Results
Book/title | //book/price	Select 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 the title element of all book elements 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	Select all ancestors of the current node (parent, grandfather, etc.)
Ancestor-or-self	Select all ancestors of the current node (parent, grandfather, etc.) and the current node itself
Attribute	Select all properties of the current node
Child	Selects all child elements of the current node.
Descendant	Select all descendant elements (child, grandchild, etc.) for the current node.
Descendant-or-self	Selects all descendant elements (child, grandchild, etc.) 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	Select all namespace nodes for the current node
Parent	Select 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, the pathLocation path expression

The location path can be absolute or relative.

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

/step/step/...

step/step/...

Each step is computed according to the nodes in the current node set. Steps (step) include:

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

Node Test (node-test): Identifying a node within an axis

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

The syntax of the step : axis Name:: node test [predicate]

Instance

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

7. XPath Operators

operator	Description	instance	return value
|	Calculate two node sets	Book | Cd	Returns all node sets with 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, return Fasle.
!=	Not equal to	price!=9.80	Returns true if Price is 9.90. If Price is 9.80, return Fasle.
<	Less than	price<9.80	Returns true if Price is 9.00. If Price is 9.90, return Fasle.
<=	Less than or equal to	price<=9.80	Returns true if Price is 9.00. If Price is 9.90, return Fasle.
>	Greater than	price>9.80	Returns true if Price is 9.90. If Price is 9.80, return Fasle.
>=	Greater than or equal to	price>=9.80	Returns true if Price is 9.90. If Price is 9.70, return Fasle.
Or	Or	price=9.80 or price=9.70	Returns true if Price is 9.80. If Price is 9.50, return Fasle.
and	And	price>9.00 and price<9.90	Returns true if Price is 9.80. If Price is 8.50, return Fasle.
MoD	Calculate the remainder of a division	5 MoD 2	1