Apache Xerces SAX Parser - Modify XML Document

Demo Example

Here is the input xml file we need to Modify by appending <Result>Pass<Result/>
at the end of </marks> tag

<?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>

SAXModifyDemo.java

package com.tutorialspoint.xml;

import java.io.*;
import org.xml.sax.*;
import javax.xml.parsers.*;
import org.xml.sax.helpers.DefaultHandler;

public class SAXModifyDemo extends DefaultHandler {
   static String displayText[] = new String[1000];
   static int numberLines = 0;
   static String indentation = "";

   public static void main(String args[]) {

      try { 
         File inputFile = new File("input.txt");
         SAXParserFactory factory = 
         SAXParserFactory.newInstance();
         SAXModifyDemo obj = new SAXModifyDemo();
            obj.childLoop(inputFile);
         FileWriter filewriter = new FileWriter("newfile.xml");
         for(int loopIndex = 0; loopIndex < numberLines; loopIndex++){
            filewriter.write(displayText[loopIndex].toCharArray());
            filewriter.write('\n');
            System.out.println(displayText[loopIndex].toString());
         }
         filewriter.close();
      }
      catch (Exception e) {
         e.printStackTrace(System.err);
      }
   }

   public void childLoop(File input){
      DefaultHandler handler = this;
         SAXParserFactory factory = SAXParserFactory.newInstance();
      try {
         SAXParser saxParser = factory.newSAXParser();
         saxParser.parse(input, handler);
      } catch (Throwable t) {}
   }

   public void startDocument() {
      displayText[numberLines] = indentation;
      displayText[numberLines] += "<?xml version=\"1.0\" encoding=\""+
         "UTF-8" + "\"?>";
      numberLines++;
   }

   public void processingInstruction(String target,
      String data) {
      displayText[numberLines] = indentation;
      displayText[numberLines] += "<?";
      displayText[numberLines] += target;
      if (data != null && data.length() > 0) {
         displayText[numberLines] += ' ';
         displayText[numberLines] += data;
      }
      displayText[numberLines] += "?>";
      numberLines++;
   }

   public void startElement(String uri, String localName,
      String qualifiedName, Attributes attributes) {
      displayText[numberLines] = indentation;

      indentation += "    ";

      displayText[numberLines] += '<';
      displayText[numberLines] += qualifiedName;
      if (attributes != null) {
         int numberAttributes = attributes.getLength();
         for (int loopIndex = 0; loopIndex < numberAttributes;
            loopIndex++){
            displayText[numberLines] += ' ';
            displayText[numberLines] += attributes.getQName(loopIndex);
            displayText[numberLines] += "=\"";
            displayText[numberLines] += attributes.getValue(loopIndex);
            displayText[numberLines] += '"';
         }
      }
      displayText[numberLines] += '>';
      numberLines++;
   }

   public void characters(char characters[],
      int start, int length) {
      String characterData = (new String(characters, start, length)).trim();
      if(characterData.indexOf("\n") < 0 && characterData.length() > 0) {
         displayText[numberLines] = indentation;
         displayText[numberLines] += characterData;
         numberLines++;
      }
   }

   public void endElement(String uri, String localName,
      String qualifiedName) {
      indentation = indentation.substring(0, indentation.length() - 4) ;
      displayText[numberLines] = indentation;
      displayText[numberLines] += "</";
      displayText[numberLines] += qualifiedName;
      displayText[numberLines] += '>';
      numberLines++;

      if (qualifiedName.equals("marks")) {
            startElement("", "Result", "Result", null);
            characters("Pass".toCharArray(), 0, "Pass".length());
            endElement("", "Result", "Result");
      }
   }
}

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>
        <Result>
            Pass
        </Result>
    </student>
    <student rollno="493">
        <firstname>
            Vineet
        </firstname>
        <lastname>
            Gupta
        </lastname>
        <nickname>
            Vinni
        </nickname>
        <marks>
            95
        </marks>
        <Result>
            Pass
        </Result>
    </student>
    <student rollno="593">
        <firstname>
            Jasvir
        </firstname>
        <lastname>
            Singh
        </lastname>
        <nickname>
            Jazz
        </nickname>
        <marks>
            90
        </marks>
        <Result>
            Pass
        </Result>
    </student>
</class>

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