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Using child axis in XPath expression
Posted on: September 29, 2008 at 12:00 AM

In this section you will know about the use of "child axis". "child axis" consists of the children of context node.

Using child axis in XPath expression

In this section you will know about the use of "child axis". "child axis" consists of the children of context node. It can be omitted as well because it is the default axis you may or may not use it.

In this example we have created an XML file "persons.xml" as in our previous section, which is necessary to execute XPath query on to it. This "persons.xml" contains information related to name, age, gender of different persons.

Here is the full source code for persons.xml file as follows :

persons.xml

<?xml version="1.0" ?>

      <information>

        <person id="1">

        <name>Deep</name>

        <age>34</age>

        <gender>Male</gender>

        </person>

       

       <person id="2">

        <name>Kumar</name>

        <age>24</age>

        <gender>Male</gender>

        </person>

       

        <person id="3">

        <name>Deepali</name>

        <age>19</age>

        <gender>Female</gender>

        </person>

      

        <!-- more persons... -->

      </information>

Now we have declared a class XPathChildAxis and in this class we are parsing the XML file with JAXP. First of all we need to load the document into DOM Document object. We have put that persons.xml file in that current working directory.

 
      DocumentBuilderFactory domFactory = 

        DocumentBuilderFactory.newInstance();

        domFactory.setNamespaceAware(true); 

        DocumentBuilder builder = domFactory.newDocumentBuilder();

        Document doc = builder.parse("persons.xml");

Above lines of code parses "persons.xml" file and creates a Document object. Next we have created XPath object with the use of XPathFactory.

XPath xpath = XPathFactory.newInstance().newXPath();

"//child::person/name" is as same as "//person/name".

Here is the example code for XPathChildAxis.java as follows:

XPathChildAxis.java


import org.w3c.dom.*;

import javax.xml.xpath.*;

import javax.xml.parsers.*;

import java.io.IOException;

import org.xml.sax.SAXException;



public class XPathChildAxis {



  public static void main(String[] args) 

 throws ParserConfigurationException, SAXException, 

  IOException, XPathExpressionException {



  DocumentBuilderFactory domFactory = 

      DocumentBuilderFactory.newInstance();

  domFactory.setNamespaceAware(true); 

  DocumentBuilder builder = domFactory.newDocumentBuilder();

  Document doc = builder.parse("persons.xml");

  XPath xpath = XPathFactory.newInstance().newXPath();

XPathExpression expr =

        xpath.compile("//child::person/name/text()");

  // using Child Axis 

  Object result = 

      expr.evaluate(doc, XPathConstants.NODESET);

  NodeList nodes = (NodeList) result;

  for (int i = 0; i < nodes.getLength(); i++) {

 System.out.println(nodes.item(i).getNodeValue()); 

  }  

  }

}

Output:

Download Source Code

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