Building DOM Trees Through Parsing 

Purpose

The easiest way to get a DOM Tree is to parse a XML file using a DocumentBuilder. Then you can traverse the Document object and extract what you need. The JAXP Framework provides several classes to do this. Here are two important classes related to this process:

·        javax.xml.pasers.DocumentBuilderFactory

·        javax.xml.DocumentBuilder

Process Flow

In general, all you need to do is to invoke DocumentBuilderFactory.newInstance() in order to get an instance of the DocumentBuilderFactory. Then you can use this instance to get a new DocumentBuilder – ( newDocumentBuilder()). Finally, use the DocumentBuilder instance to parse an XML file, using DocumentBuilder.parse(InputSource. You can further specify whether you want your DocumentBuilder to be validating - DocumentBuilderFactory.setValidating(boolean), or to be namespace-aware - DocumentBuilderFactory.setNamespaceAware(boolean).

Example

A short example for building trees through parsing is presented below:

public class JAXPDOMExample {   public static void main(String args[]) {     try {       String xml= "data/rich_ii.xml";       //get a DocumentBuilderFactory from the underlying       //implementation       DocumentBuilderFactory factory =       DocumentBuilderFactory.newInstance();       factory.setValidating(true);       //get a DocumentBuilder from the factory       DocumentBuilder builder = factory.newDocumentBuilder();       //parse the document       Document document = builder.parse(xml);            DOMTraverser domTester = new DOMTraverser();       domTester.traverse1(document);     } catch (Exception e) {       //if there was some error while parsing the file       e.printStackTrace();     }   }