Nodename selects all children of this node.

/Select from the root node.

//Select the nodes in the document that match the selection from the current nodes, regardless of their positions.

. Select the current node.

.. select the parent node of the current node.

@ Select an attribute.

Routing expression

result

Bookstore selects all the child nodes of the Bookstore element.

/bookstore Select the root element bookstore. Note: If the path starts with a forward slash (/), it always represents the absolute path of an element!

Bookstore/Book Select all the book elements that belong to the sub-elements of the bookstore.

//book selects all book child elements, regardless of their position in the document.

Book store//books selects all the child elements of the book element, no matter where they are located in the bookstore.

Named lang selects all attributes named lang.

for instance

1. Find page root element://

2. Find all input elements on the page: //input

3. Find the direct child input element in the first form element on the page (that is, the next-level input element containing only the form element, which is represented by an absolute path and represented by a single symbol): //form[ 1]/input.

4. Find all the child input elements in the first form element on the page (as long as the input in the form element is calculated, no matter how many other tabs are nested, it is represented by a relative path with a double//sign)://form [1]/input.

5. Find the first form element on the page: //form[ 1]

6. Find the form element with the id of loginForm on the page: //form[@id='loginForm'].

7. Find the input element whose name attribute is username on the page: //input[@name='username'].

8. On the page, find the first input element under the form element with the id of loginForm://form [@ id =' login form']/input [1].

9. The search page has an input element whose name attribute is continuous and whose type attribute is button://input [@ name =' continue'] [@ type =' button'].

10. Find all the elements with id in the web page? /@id

2. Decorate the content searched by the node.

for instance

Routing expression

result

/bookstore/book[ 1] Select the first book element that belongs to the child element of the bookstore.

/bookstore/book[last()] Select the last book element that belongs to the bookstore child element.

/book store/book [last ()-1] Select the penultimate Book element that belongs to the child element of Bookstore.

/bookstore/book[position()] Select the first two book elements that belong to the child elements of the bookstore element.

//title[@lang] Select all the title elements whose attribute name is lang.

//title[@lang='eng'] Select all the title elements, which have the lang attribute with the value of eng.

/Bookstore/Book [Price & gt35.00] Select all book elements of the bookstore element, and the value of the price element must be greater than 35.00.

/bookstore/book [price & gt35.00]/title Select all title elements of the Book element in the Book element, and the value of the Price element must be greater than 35.00.

3. Select an unknown node

wildcard character

describe

* Matches any element node.

@ * Matches any attribute node.

Node () matches any type of node.

for instance

Routing expression

result

/bookstore/* Select all the child elements of the bookstore element.

//* Select all elements in the document.

//title[@*] Select all title elements with attributes.

4. Choose several paths

You can select multiple paths by using the | operator in the path expression.

Routing expression

result

//book/title | //book/price Select all the titles and price elements of the book element.

//title | //price Select all the title and price elements in the document.

/bookstore/book/title | //price Select all title elements of the book element belonging to the bookstore element and all price elements in the document.

5. Keywords

Use case

for instance

Text () Book/Author/Text ()

String () Book/Author /string ()

Data () Books/Authors/Data ()

. A book/author/.

for instance

XML example

& ltbook & gt& lt author & gt Tom & lt/em & gt； John & lt/em > Cat</ Author & gt& lt Pricing & gt& lt Price & gt20 & lt/price & gt；; & lt discount & gt0.8 & lt/discount & gt；; & lt/pricing & gt； & lt/book & gt；

Text ()

You often see text () at the end of XPath expressions, which only returns the text content of the specified element.

The crawled xpath format is book/author/text (), and the crawled content is Tom cat, where John does not belong to the author's direct node content.

String ()

The string () function will get all the node text contents of the specified element, which will be spliced into a string.

The crawled xpath format is book/author/string (), and the crawled content is crawled from the head to the tail of Tom John Cat.

Data ()

Most of the time, the data () function and the string () function are commonly used, and frequent use of the data () function is not recommended. According to statistics, this function will affect the performance of XPath.

The crawled xpath format is book/pricing/data (), and the crawled content returns separated 20 and 0.8. Their types are not strings, but xs:anyAtomicType, so you can use mathematical functions to perform some operations.

You can only use data () when crawling all numbers, but you can't use text () or string () because XPath doesn't support strings for mathematical operations.

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