In this example, we demonstrate the use of DOM parser to modify an existing XML file :

  1. Add a new element
  2. Update existing element attribute
  3. Update existing element value
  4. Delete existing element

1. XML file

See before and after XML file.

File : file.xml – Original XML file.

<?xml version="1.0" encoding="UTF-8" standalone="no" ?> 
<company>
   <staff id="1">
	<firstname>yong</firstname>
	<lastname>mook kim</lastname>
	<nickname>mkyong</nickname>
	<salary>100000</salary>
   </staff>
</company>

Later, update above XML file via DOM XML Parser.

  1. Update the staff attribute id = 2
  2. Update salary value to 200000
  3. Append a new “age” element under staff
  4. Delete “firstname” element under staff

File : file.xml – Newly modified XML file.

<?xml version="1.0" encoding="UTF-8" standalone="no" ?> 
<company>
   <staff id="2">
	<lastname>mook kim</lastname>
	<nickname>mkyong</nickname>
	<salary>2000000</salary> 
        <age>28</age> 
   </staff>
</company>

2. DOM Parser

DOM XML parser to update an above XML file.

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 ModifyXMLFile {
 
	public static void main(String argv[]) {
 
	   try {
		String filepath = "c:\\file.xml";
		DocumentBuilderFactory docFactory = DocumentBuilderFactory.newInstance();
		DocumentBuilder docBuilder = docFactory.newDocumentBuilder();
		Document doc = docBuilder.parse(filepath);
 
		// Get the root element
		Node company = doc.getFirstChild();
 
		// Get the staff element , it may not working if tag has spaces, or
		// whatever weird characters in front...it's better to use
		// getElementsByTagName() to get it directly.
		// Node staff = company.getFirstChild();
 
		// Get the staff element by tag name directly
		Node staff = doc.getElementsByTagName("staff").item(0);
 
		// update staff attribute
		NamedNodeMap attr = staff.getAttributes();
		Node nodeAttr = attr.getNamedItem("id");
		nodeAttr.setTextContent("2");
 
		// append a new node to staff
		Element age = doc.createElement("age");
		age.appendChild(doc.createTextNode("28"));
		staff.appendChild(age);
 
		// loop the staff child node
		NodeList list = staff.getChildNodes();
 
		for (int i = 0; i < list.getLength(); i++) {
 
                   Node node = list.item(i);
 
		   // get the salary element, and update the value
		   if ("salary".equals(node.getNodeName())) {
			node.setTextContent("2000000");
		   }
 
                   //remove firstname
		   if ("firstname".equals(node.getNodeName())) {
			staff.removeChild(node);
		   }
 
		}
 
		// write the content into xml file
		TransformerFactory transformerFactory = TransformerFactory.newInstance();
		Transformer transformer = transformerFactory.newTransformer();
		DOMSource source = new DOMSource(doc);
		StreamResult result = new StreamResult(new File(filepath));
		transformer.transform(source, result);
 
		System.out.println("Done");
 
	   } catch (ParserConfigurationException pce) {
		pce.printStackTrace();
	   } catch (TransformerException tfe) {
		tfe.printStackTrace();
	   } catch (IOException ioe) {
		ioe.printStackTrace();
	   } catch (SAXException sae) {
		sae.printStackTrace();
	   }
	}
}
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