XPath Nodes

Welcome to The Coding College! In this tutorial, we will focus on XPath Nodes, which form the building blocks of navigating and querying XML documents using XPath. Understanding the types of nodes and their characteristics is crucial for efficiently working with XPath.

What Are XPath Nodes?

In XPath, everything in an XML document is represented as a node. Nodes are the fundamental units of an XML document and can represent elements, attributes, text, comments, and more.

XPath operates on these nodes to locate specific parts of an XML document.

Types of Nodes in XPath

XPath defines seven types of nodes:

Example XML Document

We will use the following XML document to explore XPath nodes:

<library>
  <book id="1" genre="Programming">
    <title>XML Basics</title>
    <author>John Doe</author>
    <description>An introductory guide to XML.</description>
  </book>
  <book id="2" genre="Programming">
    <title>Learn JavaScript</title>
    <author>Jane Smith</author>
    <description>A comprehensive guide to JavaScript programming.</description>
  </book>
  <!-- This is a comment -->
</library>

Working with Different XPath Nodes

1. Root Node

The root node represents the entire document, starting from the top level.

XPath Expression:

/

Result:
Selects the root node <library>:

<library>
  ...
</library>

2. Element Nodes

Element nodes represent the tags in the XML document.

XPath Expression:

/library/book

Result:
Selects all <book> elements:

<book id="1" genre="Programming">
  ...
</book>
<book id="2" genre="Programming">
  ...
</book>

3. Attribute Nodes

Attribute nodes represent attributes inside an element. Attributes are not part of the element’s child nodes but can be accessed using the @ symbol.

XPath Expression:

/library/book/@id

Result:
Selects the id attribute of all <book> elements:

1  
2

4. Text Nodes

Text nodes represent the content inside elements. Text nodes do not include the surrounding tags.

XPath Expression:

/library/book/title/text()

Result:
Selects the text content of all <title> elements:

XML Basics  
Learn JavaScript

5. Comment Nodes

Comment nodes represent XML comments. You can access comments using the comment() function in XPath.

XPath Expression:

//comment()

Result:
Selects all comment nodes in the document:

<!-- This is a comment -->

6. Namespace Nodes

Namespace nodes are used when an XML document includes namespaces. For example:

<library xmlns:tech="https://example.com/tech">
  <tech:book id="1">
    <tech:title>XML Guide</tech:title>
  </tech:book>
</library>

XPath Expression to Access Namespaces:

/library/namespace::*

Result:
Retrieves the xmlns:tech namespace.

7. Processing Instruction Nodes

Processing instruction nodes represent special instructions in the XML. For example:

<?xml-stylesheet type="text/xsl" href="style.xsl"?>

XPath Expression:

/processing-instruction()

Result:
Selects the processing instruction:

<?xml-stylesheet type="text/xsl" href="style.xsl"?>

Practical Examples

Example 1: Select All Book Titles

XPath Expression:

/library/book/title

Result:
Selects all <title> elements:

<title>XML Basics</title>
<title>Learn JavaScript</title>

Example 2: Select All Attributes of <book>

XPath Expression:

/library/book/@*

Result:
Selects all attributes of <book> elements:

id="1" genre="Programming"  
id="2" genre="Programming"

Example 3: Select Nodes Containing Specific Text

XPath Expression:

/library/book/description[contains(text(), 'guide')]

Result:
Selects all <description> elements containing the word “guide”:

<description>An introductory guide to XML.</description>
<description>A comprehensive guide to JavaScript programming.</description>

Example 4: Count Nodes

XPath Expression:

count(/library/book)

Result:
Counts the number of <book> elements:

2

Combining XPath Node Types

You can combine multiple node types in a single XPath expression to retrieve specific information.

Example: Get the Title of the Book with ID 1

XPath Expression:

/library/book[@id="1"]/title

Result:

<title>XML Basics</title>

Conclusion

XPath nodes provide the foundation for querying and navigating XML documents. Understanding node types like elements, attributes, and text is essential for writing powerful and efficient XPath expressions.