Java DOM4J Parser - Modify XML Document

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Demo Example

Here is the XML that 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>

DOM4jModifyXMLDemo.java

package com.howcodex.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>
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