Steps to Use DOM
Following are the steps used while parsing a document using the DOM Parser – Parse XML Document.
- Import XML-related packages.
- Create a DocumentBuilder
- Create a Document from a file or stream
- Extract the root element
- Examine attributes
- Examine sub-elements
Import XML-related packages
import org.w3c.dom.*; import javax.xml.parsers.*; import java.io.*;
Create a DocumentBuilder
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); DocumentBuilder builder = factory.newDocumentBuilder();
Create a Document from a file or stream
StringBuilder xmlStringBuilder = new StringBuilder();
xmlStringBuilder.append("<?xml version = "1.0"?> <class> </class>");
ByteArrayInputStream input = new ByteArrayInputStream(
xmlStringBuilder.toString().getBytes("UTF-8"));
Document doc = builder.parse(input);
Extract the root element
Element root = document.getDocumentElement();
Examine attributes
//returns specific attribute
getAttribute("attributeName");
//returns a Map (table) of names/values
getAttributes();
Examine sub-elements
//returns a list of subelements of specified name
getElementsByTagName("subelementName");
//returns a list of all child nodes
getChildNodes();
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>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
DomParserDemo.java
package com.adglob.xml;
import java.io.File;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.DocumentBuilder;
import org.w3c.dom.Document;
import org.w3c.dom.NodeList;
import org.w3c.dom.Node;
import org.w3c.dom.Element;
public class DomParserDemo {
public static void main(String[] args){
try {
File inputFile = new File("input.txt");
DocumentBuilderFactory dbFactory
= DocumentBuilderFactory.newInstance();
DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
Document doc = dBuilder.parse(inputFile);
doc.getDocumentElement().normalize();
System.out.println("Root element :"
+ doc.getDocumentElement().getNodeName());
NodeList nList = doc.getElementsByTagName("student");
System.out.println("----------------------------");
for (int temp = 0; temp < nList.getLength(); temp++) {
Node nNode = nList.item(temp);
System.out.println("\nCurrent Element :"
+ nNode.getNodeName());
if (nNode.getNodeType() == Node.ELEMENT_NODE) {
Element eElement = (Element) nNode;
System.out.println("Student roll no : "
+ eElement.getAttribute("rollno"));
System.out.println("First Name : "
+ eElement
.getElementsByTagName("firstname")
.item(0)
.getTextContent());
System.out.println("Last Name : "
+ eElement
.getElementsByTagName("lastname")
.item(0)
.getTextContent());
System.out.println("Nick Name : "
+ eElement
.getElementsByTagName("nickname")
.item(0)
.getTextContent());
System.out.println("Marks : "
+ eElement
.getElementsByTagName("marks")
.item(0)
.getTextContent());
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
The above program will generate 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 : Vineet Last Name : Gupta Nick Name : Vinni Marks : 95 Current Element :student Student roll no : 593 First Name : Jasvir Last Name : Singh Nick Name : Jazz Marks : 90
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