How to parse XML file using XPath parser

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XPath is used to parse a XML document whenever we know  what we have to parse like: tag name, attribute name. That means we can directly indicate and parse whatever(tag or attribute value) we want to parse.

Lets see an example:

import java.io.File;

import java.io.FileInputStream;

import java.io.IOException;

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 org.w3c.dom.Document;

import org.w3c.dom.Element;

import org.w3c.dom.Node;

import org.w3c.dom.NodeList;

import org.xml.sax.SAXException;

/**

*

* @author Kayum

*/

/**

we are going to parse the below XML file:

*

*

<company>

   <customers>

       <customer cusId="1" deskNo="1">

           <firstname>Euna</firstname>

           <lastname>Islam</lastname>

           <username>E Islam</username>

           <position>Software Engineer</position>

       </customer>

       <customer cusId="2" deskNo="2">

           <firstname>Mamun</firstname>

           <lastname>Kayum</lastname>

           <username>Mamun_Kayum</username>

           <position>Software Engineer</position>

       </customer>

       <customer cusId="3" deskNo="3">

           <firstname>Gulam</firstname>

           <lastname>Samdani</lastname>

           <username>Masum</username>

           <position>Software Engineer</position>

       </customer>

   </customers>

</company>

*/

public class XPathEX {

   public void readFile() {

       // reading the file

       ClassLoader classLoader = getClass().getClassLoader();

       File fileDir = new File(classLoader.getResource("resources/customer.xml").getFile());

       String nodeValue;

       String attributeValue;

       String firstName;

       if (fileDir.exists()) { // if the xml is exist

           System.out.println("file found");

           try {

               DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();

               DocumentBuilder db = dbf.newDocumentBuilder();

               Document document = db.parse(new FileInputStream(fileDir));// same xml comments as above.

               XPathFactory xpf = XPathFactory.newInstance();

               XPath xpath = xpf.newXPath();

               String nodeLavel = "/company/customers/customer";

               // reading attribute value

               Element userElement = (Element) xpath.evaluate(nodeLavel, document,

                       XPathConstants.NODE);



               attributeValue = userElement.getAttribute("deskNo"); // will return first child node's 'deskNo' attribute value

               System.out.println("Value of attribute 'Desk No:' " + attributeValue);

               attributeValue = userElement.getAttribute("cusId");

               System.out.println("Value of attribute 'Customer no:' " + attributeValue);

               nodeValue = userElement.getElementsByTagName("firstname").item(0).getTextContent();

               System.out.println("value of clild node 'firstname:' " + nodeValue);


               // read all child node 'firstname' values

               NodeList nodeList = (NodeList) xpath.compile(nodeLavel).evaluate(document, XPathConstants.NODESET);

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

               Node nNode = nodeList.item(i);

               Element userElementForNodes = (Element) nNode;

               nodeValue = userElementForNodes.getElementsByTagName("firstname").item(0).getTextContent();

               System.out.println("value of clild node 'firstname:' " + nodeValue);

               }


           } catch (ParserConfigurationException | SAXException | IOException | XPathExpressionException e) {

           }


       } else {

           System.out.println("file not found");

       }

   }


   public static void main(String[] args) {

       XPathEX readObj = new XPathEX();

       readObj.readFile();

   }



}

Where our XML file is:

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

<company>

   <customers>

       <customer cusId="1" deskNo="1">

           <firstname>Euna</firstname>

           <lastname>Islam</lastname>

           <username>E Islam</username>

           <position>Software Engineer</position>

       </customer>

       <customer cusId="2" deskNo="2">

           <firstname>Mamun</firstname>

           <lastname>Kayum</lastname>

           <username>Mamun_Kayum</username>

           <position>Software Engineer</position>

       </customer>

       <customer cusId="3" deskNo="3">

           <firstname>Gulam</firstname>

           <lastname>Samdani</lastname>

           <username>Masum</username>

           <position>Software Engineer</position>

       </customer>

   </customers>

</company>