How to read XML using XPath in Java

Question

I want to read XML data using XPath in Java, so for the information I have gathered I am not able to parse XML according to my requirement.

here is what I want to do

Answer 1

You can try this.

XML Document

Save as employees.xml.

    
        29
        Pankaj
        Male
        Java Developer
    
    
        35
        Lisa
        Female
        CEO
    
    
        40
        Tom
        Male
        Manager
    
    
        25
        Meghan
        Female
        Manager
    

Parser class

The class have following methods

• List item
• A Method that will return the Employee Name for input ID.
• A Method that will return list of Employees Name with age greater than the input age.
• A Method that will return list of Female Employees Name.

Source Code

import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

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.XPathExpression;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathFactory;

import org.w3c.dom.Document;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;


public class Parser {

    public static void main(String[] args) {
        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
        factory.setNamespaceAware(true);
        DocumentBuilder builder;
        Document doc = null;
        try {
            builder = factory.newDocumentBuilder();
            doc = builder.parse("employees.xml");

            // Create XPathFactory object
            XPathFactory xpathFactory = XPathFactory.newInstance();

            // Create XPath object
            XPath xpath = xpathFactory.newXPath();

            String name = getEmployeeNameById(doc, xpath, 4);
            System.out.println("Employee Name with ID 4: " + name);

            List names = getEmployeeNameWithAge(doc, xpath, 30);
            System.out.println("Employees with 'age>30' are:" + Arrays.toString(names.toArray()));

            List femaleEmps = getFemaleEmployeesName(doc, xpath);
            System.out.println("Female Employees names are:" +
                    Arrays.toString(femaleEmps.toArray()));

        } catch (ParserConfigurationException | SAXException | IOException e) {
            e.printStackTrace();
        }

    }


    private static List getFemaleEmployeesName(Document doc, XPath xpath) {
        List list = new ArrayList<>();
        try {
            //create XPathExpression object
            XPathExpression expr =
                xpath.compile("/Employees/Employee[gender='Female']/name/text()");
            //evaluate expression result on XML document
            NodeList nodes = (NodeList) expr.evaluate(doc, XPathConstants.NODESET);
            for (int i = 0; i < nodes.getLength(); i++)
                list.add(nodes.item(i).getNodeValue());
        } catch (XPathExpressionException e) {
            e.printStackTrace();
        }
        return list;
    }


    private static List getEmployeeNameWithAge(Document doc, XPath xpath, int age) {
        List list = new ArrayList<>();
        try {
            XPathExpression expr =
                xpath.compile("/Employees/Employee[age>" + age + "]/name/text()");
            NodeList nodes = (NodeList) expr.evaluate(doc, XPathConstants.NODESET);
            for (int i = 0; i < nodes.getLength(); i++)
                list.add(nodes.item(i).getNodeValue());
        } catch (XPathExpressionException e) {
            e.printStackTrace();
        }
        return list;
    }


    private static String getEmployeeNameById(Document doc, XPath xpath, int id) {
        String name = null;
        try {
            XPathExpression expr =
                xpath.compile("/Employees/Employee[@id='" + id + "']/name/text()");
            name = (String) expr.evaluate(doc, XPathConstants.STRING);
        } catch (XPathExpressionException e) {
            e.printStackTrace();
        }

        return name;
    }

}