In this example we will learn how to use the following-sibling function of XPath. We will start with the introduction of XPath – what it is and how to use it, then we will see the working model of ‘following-sibling’ function.
Tools and technologies used in this example are Java 1.7, Maven, Intellij.
1. Overview
An XPath expression specifies a pattern that selects a set of XML nodes. XSLT templates then use those patterns when applying transformations. The nodes in an XPath expression refer to more than just elements. They also refer to text and attributes, among other things. In fact, the XPath specification defines an abstract document model that defines seven kinds of nodes:
- Root
- Element
- Text
- Attribute
- Comment
- Processing instruction
- Namespace
XPath also provides rules for converting a node in an XML document object model (DOM) tree to a boolean, double, or string value. XPath is a W3C-defined language and an official W3C recommendation; the W3C hosts the XML Path Language (XPath) Version 1.0 specification.
2. XPath Expressions
An XPath expression is composed of a location path and one or more optional predicates. Expressions may also include XPath variables.
The following is an example of a simple XPath expression:
/Country/City
This example would select the <City> element in an XML document
The following-sibling function selects all siblings after the current node
3. Project Structure
Below is the project structure used in this example
4. XLM file
Below is the xml file representing Users. Each user has got a unique UserId, name, address, sex, Date Of Birth and email.
user.xml
<?xml version="1.0" encoding="UTF-8"?>
<Users>
<User>
<UserId>12345</UserId>
<Name>
<FirstName>Maden</FirstName>
<MiddleName>Over</MiddleName>
<Surname>Gulliver</Surname>
</Name>
<Address>
<FirstLineOfAddress>Oxford Street</FirstLineOfAddress>
<SecondLineOfAddress></SecondLineOfAddress>
<City>London</City>
<County>Middlesex</County>
<Country>United Kingdom</Country>
</Address>
<Sex>Male</Sex>
<DateOfBirth>01/02/1967</DateOfBirth>
<Email></Email>
</User>
<User>
<UserId>56789</UserId>
<Name>
<FirstName>Tom</FirstName>
<MiddleName>Cruise</MiddleName>
<Surname>Kidman</Surname>
</Name>
<Address>
<FirstLineOfAddress>Reagent Street</FirstLineOfAddress>
<SecondLineOfAddress></SecondLineOfAddress>
<City>New York</City>
<County></County>
<Country>United States</Country>
</Address>
<Sex>Female</Sex>
<DateOfBirth>02/03/1978</DateOfBirth>
<Email></Email>
</User>
<User>
<UserId>72638</UserId>
<Name>
<FirstName>Amitabh</FirstName>
<MiddleName></MiddleName>
<Surname>Bachchan</Surname>
</Name>
<Address>
<FirstLineOfAddress>Panama Street</FirstLineOfAddress>
<SecondLineOfAddress></SecondLineOfAddress>
<City>Mumbai</City>
<County></County>
<Country>India</Country>
</Address>
<Sex>Male</Sex>
<DateOfBirth>05/04/1999</DateOfBirth>
<Email>amitabh.bachchan@asv.com</Email>
</User>
</Users>5. Java file
Below is the java file which will use XPath to extract information from the User.xml.
ExampleXPathFollowingSibling.java
package com.javacodegeeks;
import org.w3c.dom.Document;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathFactory;
import java.io.FileNotFoundException;
import java.io.IOException;
/**
* Example class for describing how the XPath following-sibling function works.
* @author JavaCodeGeeks
*/
public class ExampleXPathFollowingSibling {
DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = null;
public static void main(String q[]) {
ExampleXPathFollowingSibling exampleXPathFollowingSibling = new ExampleXPathFollowingSibling();
exampleXPathFollowingSibling.execute();
}
public void execute() {
try {
builder = builderFactory.newDocumentBuilder();
Document document = builder.parse(this.getClass().getResourceAsStream("user.xml"));
XPath xPath = XPathFactory.newInstance().newXPath();
String expression = "//following-sibling::User[position()=3]";
NodeList nl = (NodeList) xPath.compile(expression).evaluate(document, XPathConstants.NODESET);
System.out.println(nl.item(0).getTextContent());
} catch (ParserConfigurationException e) {
e.printStackTrace();
} catch (SAXException e) {
e.printStackTrace();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (XPathExpressionException e) {
e.printStackTrace();
}
}
}First we create a reference of DocumentBuilderFactory by calling the static newInstance method of it.
DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance();
Then we create a DocumentBuilder object by calling newDocumentBuilder() method on the factory object.
DocumentBuilder builder = builderFactory.newDocumentBuilder();
Then we call the parse() method on this builder object by passing in the xml file that we want to parse.
Document document = builder.parse(this.getClass().getResourceAsStream("user.xml"));
Then we create a XPath object:
XPath xPath = XPathFactory.newInstance().newXPath();
We will call the compile() method on this XPath object by passing in the expression and then call the evaluate() method.
NodeList nl = (NodeList) xPath.compile(expression).evaluate(document, XPathConstants.NODESET);
6. Output
Run the ExampleXPathFollowingSibling.java file. Below is the generated output.
72638
Amitabh
Bachchan
Panama Street
Mumbai
India
Male
05/04/1999
amitabh.bachchan@asv.com7. Download the source file
This was an example of XPath’s following-sibling function.
You can download the full source code of this example here: XPath-following-sibling
