Apache Xerces StAX Parser - Modify XML Document

Demo Example

In order to run this example, you should have jdom.jar in your application's classpath. Download jdom-2.0.5.zip.
Here is the XML we need to modify:

<?xml version="1.0"?>
<class>
<student rollno="393">
   <firstname>Dinkar</firstname>
   <lastname>Kad</lastname>
   <nickname>Dinkar</nickname>
   <marks>85</marks>
</student>
<student rollno="493">
   <firstname>Vineet</firstname>
   <lastname>Gupta</lastname>
   <nickname>Vinni</nickname>
   <marks>95</marks>
</student>
<student rollno="593">
   <firstname>Jasvir</firstname>
   <lastname>Singh</lastname>
   <nickname>Jazz</nickname>
   <marks>90</marks>
</student>
</class>

Demo Example:
StAXModifyDemo.java

package com.tutorialspoint.xml;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.Iterator;
import java.util.List;

import javax.xml.stream.XMLEventReader;
import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.XMLStreamConstants;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.events.Attribute;
import javax.xml.stream.events.StartElement;
import javax.xml.stream.events.XMLEvent;

import org.jdom2.Document;
import org.jdom2.Element;
import org.jdom2.JDOMException;
import org.jdom2.input.SAXBuilder;
import org.jdom2.output.Format;
import org.jdom2.output.XMLOutputter;

public class StAXModifyDemo {
   public static void main(String[] args) {

      try {
         XMLInputFactory factory = XMLInputFactory.newInstance();
         XMLEventReader eventReader =
            factory.createXMLEventReader(
               new FileReader("input.txt"));
         SAXBuilder saxBuilder = new SAXBuilder();
         Document document = saxBuilder.build(new File("input.txt"));
         Element rootElement = document.getRootElement();
         List<Element> studentElements = rootElement.getChildren("student");
         while(eventReader.hasNext()){
            XMLEvent event = eventReader.nextEvent();
            switch(event.getEventType()){
               case XMLStreamConstants.START_ELEMENT:
               StartElement startElement = event.asStartElement();
               String qName = startElement.getName().getLocalPart();

               if (qName.equalsIgnoreCase("student")) {             
                  Iterator<Attribute> attributes = startElement.getAttributes();
                  String rollNo = attributes.next().getValue();               
                  if(rollNo.equalsIgnoreCase("393")){       
                     //get the student with roll no 393                     
                     for(int i=0;i < studentElements.size();i++){
                        Element studentElement = studentElements.get(i);
                        if(studentElement.getAttribute("rollno").getValue().equalsIgnoreCase("393")){
                           studentElement.removeChild("marks");
                           studentElement.addContent(new Element("marks").setText("80"));
                        }
                    }
                  }
               }       
               break;
            }      
         }
         XMLOutputter xmlOutput = new XMLOutputter();
         // display xml
         xmlOutput.setFormat(Format.getPrettyFormat());
         xmlOutput.output(document, System.out); 
      } catch (FileNotFoundException e) {
         e.printStackTrace();
      } catch (XMLStreamException e) {
         e.printStackTrace();
      } catch (JDOMException e) {
         e.printStackTrace();
      } catch (IOException e) {
         e.printStackTrace();
      }
   }
}

This would produce the following result:

<student rollno="393">
   <firstname>Dinkar</firstname>
   <lastname>Kad</lastname>
   <nickname>Dinkar</nickname>
   <marks>80</marks>
</student>
<student rollno="493">
   <firstname>Vineet</firstname>
   <lastname>Gupta</lastname>
   <nickname>Vinni</nickname>
   <marks>95</marks>
</student>
<student rollno="593">
   <firstname>Jasvir</firstname>
   <lastname>Singh</lastname>
   <nickname>Jazz</nickname>
   <marks>90</marks>
</student>