xpath 语法(节点)

(转自:http://www.w3schools.com/xpath/xpath_nodes.asp)

XPath Nodes

 

In XPath, there are seven kinds of nodes: element, attribute, text, namespace, processing-instruction, comment, and document (root) nodes.

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XPath Terminology

Nodes

In XPath, there are seven kinds of nodes: element, attribute, text, namespace, processing-instruction, comment, and document (root) nodes. XML documents are treated as trees of nodes. The root of the tree is called the document node (or root node).

Look at the following 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>

Example of nodes in the XML document above:

<bookstore>  (document node)

<author>J K. Rowling</author>  (element node)

lang="en"  (attribute node)

Atomic values

Atomic values are nodes with no children or parent.

Example of atomic values:

J K. Rowling

"en"

Items

Items are atomic values or nodes.

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Relationship of Nodes

Parent

Each element and attribute has one parent.

In the following example; the book element is the parent of the title, author, year, and price:

<book>
  
xml 代码
<book>
  <title>Harry Potter</title>
  <author>J K. Rowling</author>
  <year>2005</year>
  <price>29.99</price>
</book>
<price></price>
</book>

Children

Element nodes may have zero, one or more children.

In the following example; the title, author, year, and price elements are all children of the book element:

<book>
  
xml 代码
<book>
  <title>Harry Potter</title>
  <author>J K. Rowling</author>
  <year>2005</year>
  <price>29.99</price>
</book>

  <author></author><price>
</book>

Siblings

Nodes that have the same parent.

In the following example; the title, author, year, and price elements are all siblings:

<book>
  
xml 代码
<book>
  <title>Harry Potter</title>
  <author>J K. Rowling</author>
  <year>2005</year>
  <price>29.99</price>
</book>
<author></author><year></year><price></price>
</book>

Ancestors

A node's parent, parent's parent, etc.

In the following example; the ancestors of the title element are the book element and the bookstore element:

<bookstore></bookstore>

<book><author></author><year></year><price></price>
xml 代码
xml 代码
<bookstore>

<book>
  <title>Harry Potter</title>
  <author>J K. Rowling</author>
  <year>2005</year>
  <price>29.99</price>
</book>

</bookstore>

</book>

Descendants

A node's children, children's children, etc.

In the following example; descendants of the bookstore element are the book, title, author, year, and price elements:

<bookstore></bookstore>

<book>
 <price>
xml 代码
<bookstore>

<book>
  <title>Harry Potter</title>
  <author>J K. Rowling</author>
  <year>2005</year>
  <price>29.99</price>
</book>

</bookstore>
</price>
</book>