Java DOM4J Parser - Modify XML Document

Demo Example

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>Vaneet</firstname>
      <lastname>Gupta</lastname>
      <nickname>vinni</nickname>
      <marks>95</marks>
   </student>
   <student rollno="593">
      <firstname>jasvir</firstname>
      <lastname>singn</lastname>
      <nickname>jazz</nickname>
      <marks>90</marks>
   </student>
</class>

Demo Example:
DOM4jModifyXMLDemo.java

package com.tutorialspoint.xml;

import java.io.File;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.util.Iterator;
import java.util.List;

import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.Node;
import org.dom4j.io.OutputFormat;
import org.dom4j.io.SAXReader;
import org.dom4j.io.XMLWriter;

public class DOM4jModifyXMLDemo {
   public static void main(String[] args) {
      try {
         File inputFile = new File("input.txt");
         SAXReader reader = new SAXReader();
         Document document = reader.read( inputFile );

         Element classElement = document.getRootElement();

         List<Node> nodes = document.selectNodes("/class/student[@rollno='493']" );         
         for (Node node : nodes) {
            Element element = (Element)node;
            Iterator<Element> iterator=element.elementIterator("marks");
            while(iterator.hasNext()){
               Element marksElement=(Element)iterator.next();
               marksElement.setText("80");
            }
         }

         // Pretty print the document to System.out
         OutputFormat format = OutputFormat.createPrettyPrint();
         XMLWriter writer;
         writer = new XMLWriter( System.out, format );
         writer.write( document );
      } catch (DocumentException e) {
         e.printStackTrace();
      } catch (UnsupportedEncodingException e) {         
         e.printStackTrace();
      } catch (IOException e) {
         e.printStackTrace();
      }
   } 
}

This would produce the following result:

<?xml version="1.0" encoding="UTF-8"?>
<class> 
  <student rollno="393"> 
    <firstname>dinkar</firstname>  
    <lastname>kad</lastname>  
    <nickname>dinkar</nickname>  
    <marks>85</marks> 
  </student>  
  <student rollno="493"> 
    <firstname>Vaneet</firstname>  
    <lastname>Gupta</lastname>  
    <nickname>vinni</nickname>  
    <marks>80</marks> 
  </student>  
  <student rollno="593"> 
    <firstname>jasvir</firstname>  
    <lastname>singn</lastname>  
    <nickname>jazz</nickname>  
    <marks>90</marks> 
  </student> 
</class>