Simple modification of XML file using Java

Pretty easy using the default document classes provided by the JDK. I would prefer to use XPath on this particular item because it is easy to adapt to changes in the DOM.

First parse your document and place in a org.w3c.dom.Document class

DocumentBuilder builder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
Document document = builder.parse(new File("path to your file"));

Then I would create my XPath object that will get the version number to the item I want to change. This XPath query will find the version node where a sibling node named files value is set to cisco-upgrade_v1_5.jar.

XPath xPath = XPathFactory.newInstance().newXPath();
Node ciscoVersion = (Node)xPath.evaluate("/jnlp/resource/pattern/version-id[../file='cisco-upgrade_v1_5.jar']", 
    document.getDocumentElement(), 
    XPathConstants.NODE);

Set the new version number

ciscoVersion.setTextContent("1.5.2");

So now we have the version number changed for the cisco-upgrade_v1_5.jar entry we can output our result

TransformerFactory tranFactory = TransformerFactory.newInstance();  
Transformer aTransformer = tranFactory.newTransformer();  
Source src = new DOMSource(document);  
Result dest = new StreamResult(new FileOutputStream(new File("path to your file")));  
aTransformer.transform(src, dest);  

For convenience here is a list of imports you will need to implement this

import java.io.File;
import java.io.FileOutputStream;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.transform.Result;
import javax.xml.transform.Source;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathFactory;

import org.w3c.dom.Document;
import org.w3c.dom.Node;

One of the best way, i know is using the SAX Parser.

DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory.newInstance();

Yes, we can implement without id, but not reference.

I mean to say, we can even fetch the element using

Node nodeRef  doc.getElementsByTagName("pattern")[0];// fetches the first record.

NodeList nodes = nodeRef.getChildNodes();//loop the nodes and find the matches to replace the text.

Using Node we can access the Elements, where you will have the scope to change the content of the element.

Read more about - Node, NodeList,NamedNodeMap ,Element.