Nikos Maravitsas

About Nikos Maravitsas

Nikos has graduated from the Department of Informatics and Telecommunications of The National and Kapodistrian University of Athens. Currently, his main interests are system’s security, parallel systems, artificial intelligence, operating systems, system programming, telecommunications, web applications, human – machine interaction and mobile development.

Modify XML File in Java using DOM parser example

With this tutorial we shall show you you can read and modify the contents of an XML File using a DOM parser. The basic idea is pretty straight forward. You read the XML File and use a DOM parser to parse it and construct the DOM object in the memory. Then you can just select any item you want from the elements and the nodes list and change their values.

Of course you can also add or remove nodes from the XML Tree structure.

So here is what we are going to do:

  • We are going to use Document.getElementsByTagName() to get the elements of the document with specific tag name.
  • Use Node.getAttributes() to get a NamedNodeMap of the element’s attributes.
  • Use NamedNodeMap.getNamedItem to get a specific attributes by name.
  • Use Node.setTextContent() to set the value of that specific attributes.
  • Use Node.removeChild or Node.addChild in order to remove or add a new property for the specific element.

Here is our simple XML file that we are going to use to demonstrate all this:

testFile.xml:

<?xml version="1.0"?>
<company>

	<employee id="1">
		<firstname>James</firstname>
		<lastname>Harley</lastname>
        <email>james@example.org</email>
		<department>Human Resources</department>
		<salary>1000</salary>
	</employee>

	<employee id="2">
		<firstname>John</firstname>
		<lastname>May</lastname>
		<email>john@example.org</email>
		<department>Logistics</department>
		<salary>400</salary>
	</employee>

</company>

ReadAndModifyXMLFile.java:

package com.javacodegeeks.java.core;

import java.io.File;
import java.io.IOException;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NamedNodeMap;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;

public class ReadAndModifyXMLFile {

	public static final String xmlFilePath = "C:\\Users\\nikos7\\Desktop\\files\\testFile.xml";

	public static void main(String argv[]) {

		try {

			DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory.newInstance();

			DocumentBuilder documentBuilder = documentBuilderFactory.newDocumentBuilder();

			Document document = documentBuilder.parse(xmlFilePath);

			// Get employee by tag name
			//use item(0) to get the first node with tage name "employee"
			Node employee = document.getElementsByTagName("employee").item(0);

			// update employee , set the id to 10
			NamedNodeMap attribute = employee.getAttributes();
			Node nodeAttr = attribute.getNamedItem("id");
			nodeAttr.setTextContent("10");

			// append a new node to the first employee
			Element address = document.createElement("address");

			address.appendChild(document.createTextNode("34 Stanley St."));

			employee.appendChild(address);

			// loop the employee node and update salary value, and delete a node
			NodeList nodes = employee.getChildNodes();

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

				Node element = nodes.item(i);

				if ("salary".equals(element.getNodeName())) {
					element.setTextContent("2000000");
				}

				// remove firstname
				if ("firstname".equals(element.getNodeName())) {
					employee.removeChild(element);
				}

			}

			// write the DOM object to the file
			TransformerFactory transformerFactory = TransformerFactory.newInstance();

			Transformer transformer = transformerFactory.newTransformer();
			DOMSource domSource = new DOMSource(document);

			StreamResult streamResult = new StreamResult(new File(xmlFilePath));
			transformer.transform(domSource, streamResult);

			System.out.println("The XML File was ");

		} catch (ParserConfigurationException pce) {
			pce.printStackTrace();
		} catch (TransformerException tfe) {
			tfe.printStackTrace();
		} catch (IOException ioe) {
			ioe.printStackTrace();
		} catch (SAXException sae) {
			sae.printStackTrace();
		}
	}
}

Then, the updated XML File:
testFile.xml:

<?xml version="1.0" encoding="UTF-8" standalone="no"?><company>

	<employee id="10">

		<lastname>Harley</lastname>
        <email>james@example.org</email>
		<department>Human Resources</department>
		<salary>2000000</salary>
	    <address>34 Stanley St.</address><
	/employee>

	<employee id="2">
		<firstname>John</firstname>
		<lastname>May</lastname>
		<email>john@example.org</email>
		<department>Logistics</department>
		<salary>400</salary>
	</employee>

</company>

This was an example on how to Modify XML File in Java using DOM parser.

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