致命行动38:XPath Syntax
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from:w3cschool
XPath Syntax
« Previous Next Chapter »XPath uses path expressions to select nodes or node-sets in an XML document.The node is selected by following a path or steps.
The XML Example Document
We will use the following XML document in the examples below.
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 usefulpath expressions are listed below:
In the table below we have listed some path expressions and the result of theexpressions:
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 langPredicates
Predicates are used to find a specific node or a node that contains a specific value.
Predicates are always embedded in square brackets.
In the table below we have listed some path expressions with predicates and the result of theexpressions:
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 35.00Selecting Unknown Nodes
XPath wildcards can be used to select unknown XML elements.
In the table below we have listed some path expressions and the result of theexpressions:
Selecting Several Paths
By using the | operator in an XPath expression you can select several paths.
In the table below we have listed some path expressions and the result of theexpressions: