Java JDOM Parser - Parse XML Document

Steps to Using JDOM

Following are the steps used while parsing a document using JDOM Parser.

• Import XML-related packages.
• Create a SAXBuilder
  
• Create a Document from a file or stream
• Extract the root element
• Examine attributes
• Examine sub-elements

Import XML-related packages

import java.io.*;
import java.util.*;
import org.jdom2.*;

Create a DocumentBuilder

SAXBuilder saxBuilder = new SAXBuilder();

Create a Document from a file or stream

File inputFile = new File("input.txt");
SAXBuilder saxBuilder = new SAXBuilder();
Document document = saxBuilder.build(inputFile);

Extract the root element

Element classElement = document.getRootElement();

Examine attributes

//returns specific attribute
getAttribute("attributeName"); 

Examine sub-elements

//returns a list of subelements of specified name
getChildren("subelementName"); 
//returns a list of all child nodes
getChildren(); 
//returns first child node
getChild("subelementName"); 

Demo Example

Here is the input xml file we need to parse:

<?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:
DomParserDemo.java

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

import org.jdom2.Attribute;
import org.jdom2.Document;
import org.jdom2.Element;
import org.jdom2.JDOMException;
import org.jdom2.input.SAXBuilder;


public class JDomParserDemo {
   public static void main(String[] args) {
      try {
         File inputFile = new File("input.txt");

         SAXBuilder saxBuilder = new SAXBuilder();

         Document document = saxBuilder.build(inputFile);

         System.out.println("Root element :" 
            + document.getRootElement().getName());

         Element classElement = document.getRootElement();

         List<Element> studentList = classElement.getChildren();
         System.out.println("----------------------------");

         for (int temp = 0; temp < studentList.size(); temp++) {    
            Element student = studentList.get(temp);
            System.out.println("\nCurrent Element :" 
               + student.getName());
            Attribute attribute =  student.getAttribute("rollno");
            System.out.println("Student roll no : " 
               + attribute.getValue() );
            System.out.println("First Name : " + student.getChild("firstname").getText());
            System.out.println("Last Name : "+ student.getChild("lastname").getText());
            System.out.println("Nick Name : "+ student.getChild("nickname").getText());
            System.out.println("Marks : "+ student.getChild("marks").getText());               
         }
      }catch(JDOMException e){
         e.printStackTrace();
      }catch(IOException ioe){
         ioe.printStackTrace();
      }
   }
}

This would produce the following result:

Root element :class
----------------------------

Current Element :student
Student roll no : 393
First Name : dinkar
Last Name : kad
Nick Name : dinkar
Marks : 85

Current Element :student
Student roll no : 493
First Name : Vaneet
Last Name : Gupta
Nick Name : vinni
Marks : 95

Current Element :student
Student roll no : 593
First Name : jasvir
Last Name : singn
Nick Name : jazz
Marks : 90