XPath Tutorial: Complete Guide

XPath (XML Path Language) is a query language for selecting nodes from XML documents. It provides a powerful, concise syntax to navigate XML structure, extract data, and test conditions. XPath is used in XSLT transformations, XML Schema assertions, web scraping, and many XML processing tasks.

This comprehensive tutorial covers XPath from basics to advanced techniques. You'll learn path expressions, axes, predicates, functions, and real-world patterns. By the end, you'll be able to write efficient XPath queries for any XML document.

What is XPath?

XPath treats an XML document as a tree of nodes. Each element, attribute, and text value is a node. XPath expressions navigate this tree to select specific nodes.

<?xml version="1.0" encoding="UTF-8"?>
<bookstore>
  <book id="1" category="fiction">
    <title lang="en">The Great Gatsby</title>
    <author>F. Scott Fitzgerald</author>
    <year>1925</year>
    <price>10.99</price>
  </book>
  
  <book id="2" category="fiction">
    <title lang="en">1984</title>
    <author>George Orwell</author>
    <year>1949</year>
    <price>8.99</price>
  </book>
  
  <book id="3" category="programming">
    <title lang="en">Clean Code</title>
    <author>Robert C. Martin</author>
    <year>2008</year>
    <price>45.99</price>
  </book>
  
  <book id="4" category="programming">
    <title lang="en">Design Patterns</title>
    <author>Gang of Four</author>
    <year>1994</year>
    <price>54.99</price>
  </book>
</bookstore>

Basic Path Expressions

XPath uses path expressions similar to file system paths. / separates path steps, and you navigate from the document root or current node.

Predicates: Filtering Results

Predicates filter node selections using conditions inside square brackets [].

<!-- AND: Both conditions must be true -->
//book[price>20 and @category='programming']
//  Result: Books that are programming AND price > 20
//  Matches: Clean Code ($45.99), Design Patterns ($54.99)

<!-- OR: Either condition can be true -->
//book[year<1950 or year>2000]
//  Result: Books published before 1950 OR after 2000
//  Matches: The Great Gatsby (1925), 1984 (1949), Clean Code (2008)

<!-- Complex: Combine multiple conditions -->
//book[@category='fiction' and price<10]
//  Result: Fiction books under $10
//  Matches: 1984 ($8.99)

XPath Axes: Navigating Relationships

Axes define the relationship between the current node and the nodes you want to select. They provide precise control over navigation.

<!-- Example: From a <title> node, find the parent book's price -->

<!-- Starting from: <title>The Great Gatsby</title> -->

<!-- Method 1: Using parent axis -->
parent::book/price
//  Result: <price>10.99</price>

<!-- Method 2: Using .. shortcut -->
../price
//  Result: <price>10.99</price>

<!-- Example: Find all books after the first one -->
//book[1]/following-sibling::book
//  Result: books with id 2, 3, 4

XPath Functions

XPath includes built-in functions for string manipulation, numeric operations, and boolean logic.

<!-- contains(): Check if string contains substring -->
//book[contains(author, 'Orwell')]
//  Result: Books by authors containing "Orwell"

<!-- starts-with(): Check string prefix -->
//book[starts-with(title, 'The')]
//  Result: "The Great Gatsby"

<!-- string-length(): Get string length -->
//book[string-length(title) > 15]
//  Result: Books with titles longer than 15 characters

<!-- substring(): Extract substring -->
substring(//book[1]/title, 1, 3)
//  Result: "The" (first 3 characters)

<!-- concat(): Concatenate strings -->
concat(//book[1]/author, ' - ', //book[1]/title)
//  Result: "F. Scott Fitzgerald - The Great Gatsby"

<!-- normalize-space(): Remove extra whitespace -->
normalize-space('  Clean  Code  ')
//  Result: "Clean Code"

<!-- translate(): Character replacement -->
translate(//book[1]/title, 'aeiou', 'AEIOU')
//  Result: "ThE grEAt gAtsby" (vowels to uppercase)

<!-- sum(): Add values -->
sum(//book/price)
//  Result: 120.96 (10.99 + 8.99 + 45.99 + 54.99)

<!-- count(): Count nodes -->
count(//book)
//  Result: 4

<!-- number(): Convert to number -->
//book[number(year) > 2000]
//  Result: Books after year 2000

<!-- floor(), ceiling(), round() -->
floor(45.99)   //  Result: 45
ceiling(45.99) //  Result: 46
round(45.99)   //  Result: 46

<!-- not(): Logical NOT -->
//book[not(@category='fiction')]
//  Result: Programming books (non-fiction)

<!-- true() / false(): Boolean literals -->
//book[price > 20 and true()]
//  Result: Books over $20

<!-- boolean(): Convert to boolean -->
//book[boolean(@id)]
//  Result: All books with id attribute

<!-- name(): Get element name -->
//book[1]/*[name()='title']
//  Result: <title> element

<!-- position(): Current position -->
//book[position() mod 2 = 0]
//  Result: Even-positioned books (2nd, 4th)

<!-- last(): Last position -->
//book[position() = last()]
//  Result: Last book

<!-- text(): Get text content -->
//book[1]/title/text()
//  Result: "The Great Gatsby"

Real-World XPath Patterns

<!-- Books more expensive than $50 -->
//book[price > 50]
//  Result: Design Patterns ($54.99)

<!-- Top 2 most expensive books -->
//book[price >= //book[position()=1]/price or position() <= 2]
//  (More complex: requires XPath 2.0 for sorting)

<!-- All fiction books -->
//book[@category='fiction']

<!-- All programming books -->
//book[@category='programming']

<!-- Count books per category -->
count(//book[@category='fiction'])
//  Result: 2

<!-- Fiction books under $10 -->
//book[@category='fiction' and price < 10]
//  Result: 1984 ($8.99)

<!-- Books from 1900s (1900-1999) -->
//book[year >= 1900 and year < 2000]
//  Result: The Great Gatsby (1925), 1984 (1949), Design Patterns (1994)

<!-- Books with specific title pattern -->
//book[contains(title, 'Code') or contains(title, 'Pattern')]
//  Result: Clean Code, Design Patterns

<!-- Extract all product prices -->
//div[@class='product']//span[@class='price']

<!-- Find "Add to Cart" button for specific product -->
//div[contains(text(),'iPhone 15')]//button[text()='Add to Cart']

<!-- Get all links in navigation menu -->
//nav[@id='main-menu']//a/@href

<!-- Extract table data -->
//table[@id='results']//tr[position()>1]/td[2]

<!-- Find element by partial text -->
//button[contains(text(), 'Submit')]

XPath Best Practices

Related Tools & Resources

External References

Conclusion

XPath is an essential tool for working with XML documents. Whether you're parsing data, transforming documents with XSLT, scraping websites, or validating XML schemas, XPath provides a powerful and concise way to navigate and query XML structure.

Start with basic path expressions and gradually master predicates, axes, and functions. Practice on real XML documents to build intuition. Use browser DevTools to test queries interactively. With XPath in your toolkit, you can efficiently extract, transform, and validate XML data in any project.