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XML and XPath


What is XPath?

XPath is a major element in the XSLT standard.

XPath can be used to navigate through elements and attributes in an XML document.


XPath
  • XPath is a syntax for defining parts of an XML document
  • XPath uses path expressions to navigate in XML documents
  • XPath contains a library of standard functions
  • XPath is a major element in XSLT and in XQuery
  • XPath is a W3C recommendation

XPath Path Expressions

XPath uses path expressions to select nodes or node-sets in an XML document. These path expressions look very much like the expressions you see when you work with a traditional computer file system.

XPath expressions can be used in JavaScript, Java, XML模式, PHP, Python, C and C++, and lots of other languages.


XPath is Used in XSLT

XPath is a major element in the XSLT standard.

With XPath knowledge you will be able to take great advantage of XSL.



XPath Example

We will use the following XML document:

<?xml version="1.0" encoding="UTF-8"?>

<bookstore>

<book category="cooking">
  <title lang="en">Everyday Italian</title>
  <author>Giada De Laurentiis</author>
  <year>2005</year>
  <price>30.00</price>
</book>

<book category="children">
  <title lang="en">Harry Potter</title>
  <author>J K. Rowling</author>
  <year>2005</year>
  <price>29.99</price>
</book>

<book category="web">
  <title lang="en">XQuery Kick Start</title>
  <author>James McGovern</author>
  <author>Per Bothner</author>
  <author>Kurt Cagle</author>
  <author>James Linn</author>
  <author>Vaidyanathan Nagarajan</author>
  <year>2003</year>
  <price>49.99</price>
</book>

<book category="web">
  <title lang="en">Learning XML</title>
  <author>Erik T. Ray</author>
  <year>2003</year>
  <price>39.95</price>
</book>

</bookstore>

In the table below we have listed some XPath expressions and the result of the expressions:

XPath Expression Result
/bookstore/book[1] Selects the first book element that is the child of the bookstore element
/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='en'] Selects all the title elements that have a "lang" attribute with a value of "en"
/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 35.00

XPath 教程

You will learn a lot more about XPath in our XPath Tutorial.





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